Chapter 3. Linux Commands

aclocal [options]

Options

--acdir=dir

Look for macro files in directory dir instead of the default directory.

--help

Print help message, then exit.

--output=file

Save output to file instead of aclocal.m4.

--print-ac-dir

Print the name of the directory to be searched for m4 files, then exit.

--verbose

Print names of files being processed.

--version

Print version number, then exit.

-I dir

Additionally, search directory dir for m4 macro definitions.

addr2line [options] [addresses]

Options

-b bfdname, --target=bfdname

Set the binary file format using its binary file descriptor name, bfdname. Use the -h option for a list of supported formats for your system.

-C, --demangle[=style]

Decode (demangle) low-level symbol names into user names. See the -h help output for a list of styles supported by your compiler.

-e file, --exe=file

Specify the filename of the executable to use. The default is a.out.

-f, --functions

Display function names in addition to filenames and line numbers.

-h, --help

Display help information and exit.

-s, --basenames

Strip directories off filenames and show only the basenames.

agetty [options] port baudrate [term]

Options

-f file

Specify the use of file instead of /etc/issue upon connection to terminal. It is overridden by -i.

-h

Specify hardware, not software, flow control.

-H hostname

Write login hostname into the utmp file. By default, no login host is specified.

-I string

Specify string to be sent to tty or modem.

-i

Suppress printing of /etc/issue before printing the login prompt.

-l program

Specify the use of program instead of /bin/login.

-m

Attempt to guess the appropriate baud rate.

-n

Don't prompt for a login name.

-t timeout

Specify that agetty should exit if the open on the line succeeds and there is no response to the login prompt in timeout seconds.

-L

Do not require carrier detect; operate locally only. Use this when connecting terminals.

-w

Wait for carriage return or linefeed before sending login prompt. Use when sending an initialization string.

apmd [options]

Options

-c n, --check n

Set the number of seconds to wait for an event before rechecking the power level. Default is to wait indefinitely. Setting this causes the battery levels to be checked more frequently.

-P command, --apmd_proxy command

Specify the apmd_proxy command to run when APM driver events are reported. This is generally a shell script. The command will be invoked with parameters indicating what kind of event was received. The parameters are listed in the next section.

-p n, --percentage n

Log information whenever the power changes by n percent. The default is 5. Values greater than 100 will disable logging of power changes.

-V, --version

Print version and exit.

-v, --verbose

Verbose mode; all events are logged.

-W, --wall

Use wall to alert all users of a low battery status.

-w n, --warn n

Log a warning at ALERT level when the battery charge drops below n percent. The default is 10. Negative values disable low battery level warnings.

-q, --quiet

Disable low battery level warnings.

-?, --help

Print help summary and exit.

Parameters

The apmd proxy script will be invoked with the following parameters:

start

Invoked when the daemon starts.

stop

Invoked when the daemon stops.

suspend [ system | user ]

Invoked when a suspend request has been made. The second parameter indicates whether the request was made by the system or by the user.

standby [ system | user ]

Invoked when a standby request has been made. The second parameter indicates whether the request was made by the system or by the user.

resume [ suspend | standby | critical ]

Invoked when the system resumes normal operation. The second parameter indicates the mode the system was in before resuming. critical suspends indicate an emergency shutdown. After a critical suspend the system may be unstable, and you can use the resume command to help you recover from the suspension.

change power

Invoked when system power is changed from AC to battery or from battery to AC.

change battery

Invoked when the APM BIOS driver reports that the battery is low.

change capability

Invoked when the APM BIOS driver reports that some hardware that affects its capability has been added or removed.

apropos string ...

apt

ar key [args] [posname] [count] archive [files]

Keys

d

Delete files from archive.

m

Move files to end of archive.

p

Print files in archive.

q

Append files to archive.

r

Replace files in archive.

t

List the contents of archive or list the named files.

x

Extract contents from archive or only the named files.

Arguments

a

Use with r or m key to place files in the archive after posname.

b

Same as a, but before posname.

c

Create archive silently.

f

Truncate long filenames.

i

Same as b.

l

For backward compatibility; meaningless in Linux.

N

Use count parameter. Where multiple entries with the same name are found, use the count instance.

o

Preserve original timestamps.

P

Use full pathname. Useful for non-POSIX-compliant archives.

s

Force regeneration of archive symbol table (useful after running strip).

S

Do not regenerate symbol table.

u

Use with r to replace only files that have changed since being put in archive.

v

Verbose; print a description of actions taken.

V

Print version number.

Example

Replace mylib.a with object files from the current directory:

ar r mylib.a `ls *.o`

arch

Print machine architecture type to standard output. Equivalent to uname -m.

arp [options]

Options

host option arguments may be given as either a hostname or an IP address. When using the -D option, they may also be given as a hardware interface address (e.g., eth0, eth1).

-a [hosts], --display [hosts]

Display entries for hosts or, if none are specified, all entries.

-d host, --delete host

Remove the specified host's entry.

-D, --use-device

Use the hardware address associated with the specified interface. This may be used with -s when creating a proxy entry.

-d host [pub], --delete host [pub]

Remove host's entry. To delete a proxy entry, use the pub argument and specify the interface associated with the proxy using -i.

-f file, --file file

Read entries from file and add them.

-H type, --hw-type type, -t type

Search for type entries when examining the ARP cache. type is usually ether (Ethernet), which is the default, but may be ax25 (AX.25 packet radio), arcnet (ARCnet), pronet (PROnet), or netrom (NET/ROM).

-i interface, --device interface

Select an interface. If you are dumping the ARP cache, this option will cause the command to display only the entries using that interface. When setting entries, this will cause the interface to be associated with that entry. If you do not use this option when setting an entry, the kernel will guess.

-n, --numeric

Display host IP addresses instead of their domain names.

-s host hardware-address [netmask mask] [pub], --set host hardware-address [netmask mask] [pub]

Add a permanent entry for host at hardware-address. A hardware-address for type ether hardware is 6 hexadecimal bytes, colon-separated. The pub argument can be used to set the publish flag, creating a proxy entry. On kernels before 2.2x, you can specify a netmask on behalf of which the current system should handle requests.

-v, --verbose

Verbose mode.

Examples

Display entry for host eris:

arp -a eris

Set a permanent cache entry for host illuminati, whose hardware address you know:

arp -s illuminati 00:05:23:73:e6:cf

Set an ARP proxy for host fnord using the eth0 interface's hardware address:

arp -Ds fnord eth0 pub

Remove the fnord ARP proxy:

arp -i eth0 -d fnord pub

as [options] files

Generate an object file from each specified assembly language source file. Object files have the same root name as source files but replace the .s suffix with .o. There may be some additional system-specific options.

Options

-- [ | files]

Read input files from standard input, or from files if the pipe is used.

-a[cdhlmns][=file]

With only the -a option, list source code, assembler listing, and symbol table. The other options specify additional things to list or omit:

-ac

Omit false conditionals.

-ad

Omit debugging directives.

-ah

Include the high-level source code, if available.

-al

Include an assembly listing.

-am

Include macro expansions.

-an

Suppress forms processing.

-as

Include a symbol listing.

=file

Set the listing filename to file.

--defsym symbol=value

Define the symbol to have the value value, which must be an integer.

-f

Skip whitespace and comment preprocessing.

--fatal-warnings

Treat warnings as errors.

--gstabs

Generate stabs debugging information.

--gdwarf2

Generate DWARF2 debugging information.

-o objfile

Place output in object file objfile (default is file.o).

--statistics

Print information time and space assembler uses.

-v

Display the version number of the assembler.

-I path

Include path when searching for .include directives.

-J

Don't warn about signed overflow.

-R

Combine both data and text in text section.

-W

Don't show warnings.

-Z

Generate object file even if there are errors.

at [options] time

Execute commands at a specified time and optional date. The commands are read from standard input or from a file. (See also batch.) End input with EOF. time can be formed either as a numeric hour (with optional minutes and modifiers) or as a keyword. It can contain an optional date, formed as a month and date, a day of the week, or a special keyword (today or tomorrow). An increment can also be specified.

Options

-c job [job...]

Display the specified jobs on the standard output. This option does not take a time specification.

-d job [job...]

Delete the specified jobs. Same as atrm.

-f file

Read job from file, not from standard input.

-l

Report all jobs that are scheduled for the invoking user. Same as atq.

-m

Mail user when job has completed, regardless of whether output was created.

-q letter

Place job in queue denoted by letter, where letter is any single letter from a-z or A-Z. Default queue is a. (The batch queue defaults to b.) Higher-lettered queues run at a lower priority.

-V

Display the version number.

Time

hh:mm [modifiers]

Hours can have one digit or two (a 24-hour clock is assumed by default); optional minutes can be given as one or two digits; the colon can be omitted if the format is h, hh, or hhmm (e.g., valid times are 5, 5:30, 0530, 19:45). If modifier am or pm is added, time is based on a 12-hour clock. If the keyword zulu is added, times correspond to Greenwich Mean Time.

midnight | noon | teatime | now

Use any one of these keywords in place of a numeric time. teatime translates to 4:00 p.m.; now must be followed by an increment (described in a moment).

Date

month num[, year]

month is one of the 12 months, spelled out or abbreviated to its first three letters; num is the calendar date of the month; year is the four-digit year. If the given month occurs before the current month, at schedules that month next year.

day

One of the seven days of the week, spelled out or abbreviated to its first three letters.

today | tomorrow

Indicate the current day or the next day. If date is omitted, at schedules today when the specified time occurs later than the current time; otherwise, at schedules tomorrow.

Increment

Supply a numeric increment if you want to specify an execution time or day relative to the current time. The number should precede any of the keywords minute, hour, day, week, month, or year (or their plural forms). The keyword next can be used as a synonym of + 1.

Examples

In typical usage, you run at and input commands that you want executed at a particular time, followed by EOF.

$ at 1:00 am tomorrow
at> ./total_up > output
at> mail joe < output
at> <EOT>            Entered by pressing Ctrl-D
job 1 at 2003-03-19 01:00

The two commands could also be placed in a file and submitted as follows:

$ at 1:00 am tomorrow < scriptfile

More examples of syntax follow. Note that the first two commands are equivalent.

$ at 1945 December 9
$ at 7:45pm Dec 9
$ at 3 am Saturday
$ at now + 5 hours
$ at noon next day

atd options

System administration command. Normally started in a system startup file. Execute jobs queued by the at command.

Options

-b n

Wait at least n seconds after beginning one job before beginning the next job. Default is 60.

-d

Print error messages to standard error instead of using syslog.

-l average

When system load average is higher than average, wait to begin a new job. Default is 0.8.

-s

Process queue once, then exit.

atq [options]

List the user's pending jobs, unless the user is a privileged user; in that case, list everybody's jobs. Same as at -l, and related to batch and atrm.

Options

-q queue

Query only the specified queue and ignore all other queues.

-v

Show jobs that have completed but have not yet been deleted.

-V

Print the version number.

atrm [options] job [job...]

Delete jobs that have been queued for future execution. Same as at -d.

Options

-q queue

Remove job from the specified queue.

-V

Print the version number and then exit.

audiosend [email@address]

Send an audio recording as an email from a properly equipped workstation (Sun and Sony, with microphones). After prompting for address, subject, and Cc: fields, the program asks the user to record a message, then allows him to re-record, send, or cancel.

autoconf [options] [template_file]

Options

-d, --debug

Don't remove temporary files.

-f, --force

Replace files generated previously by autoconf.

-h, --help

Print help message, then exit.

-i, --initialization

When tracing calls with the -t option, report calls made during initialization.

-o file, --output=file

Save output to file.

-t macro, --trace=macro

Report the list of calls to macro.

-v, --verbose

Verbosely print information about the progress of autoconf.

-I dir, --include=dir

Search in directory dir for input files.

-V, --version

Print version number, then exit.

-W category, --warnings=category

Print any warnings related to category. Accepted categories are:

cross

Cross compilation.

obsolete

Obsolete constructs.

syntax

Questionable syntax.

all

All warnings.

no-category

Turn off warnings for category.

none

Turn off all warnings.

error

Treat warnings as errors.

autoheader [options] [template_file]

Options

-d, --debug

Don't remove temporary files.

-f, --force

Replace files generated previously by autoheader.

-h, --help

Print help message, then exit.

-o file, --output=file

Save output to file.

-v, --verbose

Verbosely print information about the progress of autoheader.

-I dir, --include=dir

Search in directory dir for input files.

-V, --version

Print version number, then exit.

-W category, --warnings=category

Print any warnings related to category. Accepted categories are:

obsolete

Obsolete constructs.

all

All warnings.

no-category

Turn off warnings for category.

none

Turn off all warnings.

error

Treat warnings as errors.

automake [options] [template_file]

GNU automake tool. Creates GNU standards-compliant Makefile.in files from Makefile.am template files and can be used to ensure that projects contain all files and install options required to be standards-compliant. Note that Versions 1.4 and 1.6 differ enough that many distributions include an automake14 package for backward compatibility.

Options

-a, --add-missing

Add any missing files automake requires to the directory by creating symbolic links to automake's default versions.

-c, --copy

Used with the -a option. Copy missing files instead of creating symbolic links.

--cygnus

Specifies project has a Cygnus-style source tree.

-f, --force-missing

Used with the -a option. Replace required files even if a local copy already exists.

--foreign

Treat project as a non-GNU project. Check only for elements required for proper operation.

--gnu

Treat project as a GNU project with the GNU project structure.

--gnits

A stricter version of --gnu, performing more checks to comply with GNU project structure rules.

--help

Print help message, then exit.

-i, --ignore-deps

Disable automatic dependency tracking.

--libdir=dir

Used with the -a option. Search in directory dir for default files.

--no-force

Update only Makefile.in files that have updated dependents.

-v, --verbose

List files being read or created by automake.

--version

Print version number, then exit.

-Werror

Treat warnings as errors.

autoreconf [options]

GNU autoconf tool. Update configure scripts by running autoconf, autoheader, aclocal, automake, and libtoolize in specified directories and subdirectories. This command is seldom invoked manually. It is usually called automatically from other autoconf tools.

Options

-d, --debug

Don't remove temporary files.

-f, --force

Remake all configure scripts, even when newer than their template files.

-h, --help

Print help message, then exit.

-i, --install

Add any default files missing from package by copying versions included with autoconf and automake.

-s, --symlink

Used with the -i option. Create symbolic links to default files instead of copying them.

-v, --verbose

Verbosely print information about the progress of autoreconf.

-I dir, --include=dir

Search in directory dir for input files.

-V, --version

Print version number, then exit.

-W category, --warnings=category

Print any warnings related to category. Accepted categories are:

cross

Cross compilation.

obsolete

Obsolete constructs.

syntax

Questionable syntax.

all

All warnings.

no-category

Turn off warnings for category.

none

Turn off all warnings.

error

Treat warnings as errors.

autoscan [options] [directory]

GNU autoconf tool. Create or maintain a preliminary configure.ac file named configure.scan based on source files in specified directory, or current directory if none given. If a configure.ac file already exists, autoconf will check it for completeness and print suggestions for correcting any problems it finds.

Options

-d, --debug

Don't remove temporary files.

-h, --help

Print help message, then exit.

-v, --verbose

Verbosely print information about the progress of autoscan.

-I dir, --include=dir

Search in directory dir for input files. Use multiple times to add multiple directories.

-B dir, --prepend-include=dir

Search dir for input files before searching in other directories. Use multiple times to add multiple directories.

-V, --version

Print version number, then exit.

autoupdate [options] [file]

GNU autoconf tool. Update the configure template file file, or configure.ac if no file is specified. This command is seldom invoked manually. It is usually called automatically from other autoconf tools.

Options

-d, --debug

Don't remove temporary files.

-f, --force

Remake all configure scripts, even when newer than their template files.

-h, --help

Print help message, then exit.

-v, --verbose

Verbosely print information about the progress of autoupdate.

-I dir, --include=dir

Search in directory dir for input files.

-V, --version

Print version number, then exit.

badblocks [options] device block-count

System administration command. Search device for bad blocks. You must specify the number of blocks on the device (block-count).

Options

-b blocksize

Expect blocksize-byte blocks.

-c blocksize

Test blocksize-byte blocks at a time. Default is 16.

-f

Force a read/write or nondestructive write test on a mounted device. Use only when /etc/mtab incorrectly reports a device as mounted.

-i file

Skip test of known bad blocks listed in file.

-n

Perform a nondestructive test by writing to each block and then reading back from it while preserving data.

-o file

Direct output to file.

-p number

Repeat search of device until no new bad blocks have been found in number passes. Default is 0.

-v

Verbose mode.

-w

Test by writing to each block and then reading back from it.

banner [option] [characters]

Print characters as a poster. If no characters are supplied, banner prompts for them and reads an input line from standard input. By default, the results go to standard output, but they are intended to be sent to a printer.

Option

-w width

Set width to width characters. Note that if your banner is in all lowercase, it will be narrower than width characters. If -w is not specified, the default width is 132. If -w is specified but width is not provided, the default is 80.

Example

/usr/games/banner -w50 Happy Birthday! |lpr

basename name [suffix]
basename option

Remove leading directory components from a path. If suffix is given, remove that also. The result is printed to standard output.

Options

--help

Print help message and then exit.

--version

Print the version number and then exit.

Examples

 basename /usr/lib/libm.a
libm.a

% basename /usr/lib/libm.a .a
libm

bash [options] [file [arguments]]
sh [options] [file [arguments]]

batch [options] [time]

Execute commands entered on standard input. If time is omitted, execute commands when the system load permits (when the load average falls below 0.8). Very similar to at, but does not insist that the execution time be entered on the command line. See at for details.

Options

-f file

Read job from file, not standard input.

-m

Mail user when job has completed, regardless of whether output was created.

-q letter

Place job in queue denoted by letter, where letter is one letter from a-z or A-Z. The default queue is b. (The at queue defaults to a.) Higher-lettered queues run at a lower priority.

-V

Print the version number and then exit.

-v

Display the time a job will be executed.

bc [options] [files]

bc is a language (and compiler) whose syntax resembles that of C, but with unlimited-precision arithmetic. bc consists of identifiers, keywords, and symbols, which are briefly described in the following entries. Examples are given at the end.

Options

-h, --help

Print help message and exit.

-i, --interactive

Interactive mode.

-l, --mathlib

Make functions from the math library available.

-s, --standard

Ignore all extensions, and process exactly as in POSIX.

-w, --warn

When extensions to POSIX bc are used, print a warning.

-q, --quiet

Do not display welcome message.

-v, --version

Print version number.

Identifiers

x

Variable x.

x[i]

Element i of array x. i can range from 0 to 2047 and can also be an expression.

x(y,z)

Call function x with parameters y and z.

Input-output keywords

ibase = n

Numbers that are input (e.g., typed) are read as base n (default is 10).

obase = n

Numbers that are displayed are in base n (default is 10). Note: once ibase has been changed from 10, use A to restore ibase or obase to decimal.

scale = n

Display computations using n decimal places (default is 0, meaning that results are truncated to integers). scale is normally used only for base-10 computations.

last

Value of last printed number.

Statement keywords

A semicolon or a newline separates one statement from another. Curly braces are needed when grouping multiple statements.

if (rel-expr) {statements} [else {statements}]

Do one or more statements if relational expression rel-expr is true. Otherwise, do nothing, or if else (an extension) is specified, do alternative statements. For example:

if (x=  =y) {i = i + 1} else {i = i - 1}

while (rel-expr) {statements}

Repeat one or more statements while rel-expr is true; for example:

while (i>0) {p = p*n; q = a/b; i = i-1}

for (expr1; rel-expr; expr2) {statements}

Similar to while; for example, to print the first 10 multiples of 5, you could type:

for (i=1; i<=10; i++) i*5

GNU bc does not require three arguments to for. A missing argument 1 or 3 means that those expressions will never be evaluated. A missing argument 2 evaluates to the value 1.

break

Terminate a while or for statement.

print list

GNU extension. It provides an alternate means of output. list consists of a series of comma-separated strings and expressions; print displays these entities in the order of the list. It does not print a newline when it terminates. Expressions are evaluated, printed, and assigned to the special variable last. Strings (which may contain special characters, i.e., characters beginning with \) are simply printed. Special characters can be:

a

Alert or bell

b

Backspace

f

Form feed

n

Newline

r

Carriage return

q

Double quote

t

Tab

\

Backslash

continue

GNU extension. When within a for statement, jump to the next iteration.

halt

GNU extension. Cause the bc processor to quit when executed.

quit

GNU extension. Cause the bc processor to quit whether line is executed or not.

limits

GNU extension. Print the limits enforced by the local version of bc.

Function keywords

Math library functions

s(angle)

Compute the sine of angle, a constant or expression in radians.

c(angle)

Compute the cosine of angle, a constant or expression in radians.

a(n)

Compute the arctangent of n, returning an angle in radians.

e(expr)

Compute e to the power of expr.

l(expr)

Compute the natural log of expr.

j(n, x)

Compute the Bessel function of integer order n.

Operators

arithmetic

+ - * / % ^

unary

- ++ --

assignment

=+ =- =* =/ =% =^ =

relational

< <= > >= = = !=

Other symbols

/* */

Enclose comments.

( )

Control the evaluation of expressions (change precedence). Can also be used around assignment statements to force the result to print.

{ }

Use to group statements.

[ ]

Indicate array index.

"text"

Use as a statement to print text.

Examples

Note in these examples that when you type some quantity (a number or expression), it is evaluated and printed, but assignment statements produce no display.

ibase = 8       Octal input
20              Evaluate this octal number
16              Terminal displays decimal value
obase = 2       Display output in base 2 instead of base 10
20              Octal input
10000           Terminal now displays binary value
ibase = A       Restore base-10 input
scale = 3       Truncate results to 3 decimal places
8/7             Evaluate a division
1.001001000     Oops!  Forgot to reset output base to 10
obase=10        Input is decimal now, so A isn't needed
8/7
1.142           Terminal displays result (truncated)

The following lines show the use of functions:

define p(r,n){  Function p uses two arguments
auto v          v is a local variable
v = r^n         r raised to the n power
return(v)}      Value returned

scale=5
x=p(2.5,2)      x = 2.5 ^ 2
x               Print value of x
6.25
length(x)       Number of digits
3
scale(x)        Number of places right of decimal point
2

biff [arguments]

Notify user of mail arrival and sender's name. biff operates asynchronously. Mail notification works only if your system is running the comsat(8) server. The command biff y enables notification, and the command biff n disables notification. With no arguments, biff reports biff's current status.

bison [options] file

Given a file containing context-free grammar, convert into tables for subsequent parsing while sending output to file.c. This utility is to a large extent compatible with yacc, and in fact is named for it. All input files should use the suffix .y; output files will use the original prefix. All long options (those preceded by --) may instead be preceded by +.

Options

-b prefix, --file-prefix=prefix

Use prefix for all output files.

-d, --defines

Generate file.h, producing #define statements that relate bison's token codes to the token names declared by the user.

-r, --raw

Use bison token numbers, not yacc-compatible translations, in file.h.

-k, --token-table

Include token names and values of YYNTOKENS, YYNNTS, YYNRULES, and YYNSTATES in file.c.

-l, --no-lines

Exclude #line constructs from code produced in file.c. (Use after debugging is complete.)

-n, --no-parser

Suppress parser code in output, allowing only declarations. Assemble all translations into a switch statement body and print it to file.act.

-o file, --output-file=file

Output to file.

-p prefix, --name-prefix=prefix

Substitute prefix for yy in all external symbols.

-t, --debug

Compile runtime debugging code.

-v, --verbose

Verbose mode. Print diagnostics and notes about parsing tables to file.output.

-V, --version

Display version number.

-y, --yacc, --fixed-output-files

Duplicate yacc's conventions for naming output files.

bootpd [options] [configfile [dumpfile]]

Options

-c directory

Force bootpd to work in directory.

-d level

Specify the debugging level. Omitting level will increment the level by 1.

-t timeout

Specify a timeout value in minutes. A timeout value of 0 means wait forever.

Configuration file

hostname:tg=value:tg=value:tg=value

where hostname is the name of a bootp client and tg is a tag symbol. The currently recognized tags are listed in the following section.

Tags

There is also a generic tag, Tn, where n is an RFC 1048 vendor field tag number. Generic data may be represented as either a stream of hexadecimal numbers or as a quoted string of ASCII characters.

bootpgw [options] server

TCP/IP command. Internet Boot Protocol Gateway. Maintain a gateway that forwards bootpd requests to server. In addition to dealing with BOOTREPLY packets, also deal with BOOTREQUEST packets. bootpgw is normally run by /etc/inetd by including the following line in the file /etc/inetd.conf:

bootps dgram udp wait root /etc/bootpgw bootpgw

This causes bootpgw to be started only when a boot request arrives. bootpgw takes all the same options as bootpd, except -c.

bootptest [options] server [template]

TCP/IP command. Test server's bootpd daemon by sending requests every second for 10 seconds or until the server responds. Read options from the template file, if provided.

Options

-f file

Read the boot filename from file.

-h

Identify client by hardware address, not IP address.

-m magic-number

Provide magic-number as the first word of the vendor options field.

bzcmp [options] file1 file2

Apply cmp to the data from files in the bzip2 format without requiring on-disk decompression. See bzip2 and cmp for usage.

bzdiff [options] file1 file2

Apply diff to data from files in the bzip2 format without requiring on-disk decompression. See bzip2 and cmp for usage.

bzgrep [options] pattern [file...]

Apply grep to data from files in the bzip2 format without requiring on-disk decompression. See bzip2 and grep for usage.

bzip2 [options] filenames
bunzip2 [options] filenames
bzcat [option] filenames
bzip2recover filenames

File compression and decompression utility similar to gzip, but uses a different algorithm and encoding method to get better compression. bzip2 replaces each file in filenames with a compressed version of the file and with a .bz2 extension appended. bunzip2 decompresses each file compressed by bzip2 (ignoring other files, except to print a warning). bzcat decompresses all specified files to standard output, and bzip2recover is used to try to recover data from damaged files.

Additional related commands include bzcmp, which compares the contents of bzipped files; bzdiff, which creates diff (difference) files from a pair of bzip files; bzgrep, to search them; and the bzless and bzmore commands, which apply the more and less commands to bzip output as bzcat does with the cat command. See cat, cmp, diff, and grep for information on how to use those commands.

Options

--

End of options; treat all subsequent arguments as filenames.

-dig

Set block size to dig × 100KB when compressing, where dig is a single digit from 1 to 9.

-c, --stdout

Compress or decompress to standard output.

-d, --decompress

Force decompression.

-f, --force

Force overwrite of output files. Default is not to overwrite. Also forces breaking of hard links to files.

-k, --keep

Keep input files; don't delete them.

-L, --license, -V, --version

Print license and version information and exit.

-q, --quiet

Print only critical messages.

-s, --small

Use less memory, at the expense of speed.

-t, --test

Check the integrity of the files, but don't actually compress them.

-v, --verbose

Verbose mode. Show the compression ratio for each file processed. Add more -v's to increase the verbosity.

-z, --compress

Force compression, even if invoked as bunzip2 or bzcat.

--repetitive-fast, --repetitive-best

Sometimes useful in versions earlier than 0.9.5 (which has an improved sorting algorithm) for providing some control over the algorithm.

bzless [options] file

Applies less to data files in the bzip2 format without requiring on-disk decompression. See bzip2 and less for usage.

bzmore [options] file

Applies more to data files in the bzip2 format without requiring on-disk decompression. See bzip2 and more for usage.

c++ [options] files

See g++.

c++filt [options] [symbol]

Options

-_, --strip-underscores

Remove initial underscores from symbol names.

--help

Print usage information, then exit.

-j, --java

Print names using Java syntax.

-n, --no-strip-underscores

Preserve initial underscores on symbol names.

-s format, --format=format

Expect symbols to have been coded in the specified format. Format may be one of the following:

arm

C++ Annotated Reference Manual.

edg

EDG (Intel) compiler.

gnu

Gnu compiler (the default).

gnu-new-abi

Gnu compiler with the new application binary interface (for gcc 3.x.)

hp

HP compiler.

lucid

Lucid compiler.

--version

Print version number, then exit.

cal [options] [[month] year]

Print a 12-month calendar (beginning with January) for the given year, or a one-month calendar of the given month and year. month ranges from 1 to 12. year ranges from 1 to 9999. With no arguments, print a calendar for the current month.

Options

-j

Display Julian dates (days numbered 1 to 365, starting from January 1).

-m

Display Monday as the first day of the week.

-y

Display entire year.

Examples

cal 12 1995
cal 1994 > year_file

cardctl [options] command

Commands

config [socket]

Display current socket configuration.

eject [socket]

Prepare the system for the card(s) to be ejected.

ident [socket]

Display card identification information.

insert [socket]

Notify system that a card has been inserted.

reset [socket]

Send reset signal to card.

resume [socket]

Restore power to socket and reconfigure for use.

scheme [name]

Display current scheme or change to specified scheme name.

status [socket]

Display current socket status.

suspend [socket]

Shut down device and cut power to socket.

Options

-c directory

Look for card configuration information in directory instead of /etc/pcmcia.

-f file

Use file to keep track of the current scheme instead of /var/run/pcmcia-scheme.

-s file

Look for current socket information in file instead of /var/run/stab.

cardmgr [options]

System administration command. The PCMCIA card daemon. cardmgr monitors PCMCIA sockets for devices that have been added or removed. When a card is detected, it attempts to get the card's ID and configure it according to the card configuration database (usually stored in /etc/pcmcia/config). By default, cardmgr does two things when it detects a card: it creates a system log entry and it beeps. Two high beeps mean it successfully identified and configured a device. One high beep followed by one low beep means it identified the device, but was unable to configure it successfully. One low beep means it could not identify the inserted card. Information on the currently configured cards can be found in /var/run/stab.

Options

-c directory

Look for the card configuration database in directory instead of /etc/pcmcia.

-d

Use modprobe instead of insmod to load the PCMCIA device driver.

-f

Run in the foreground to process the current cards, then run as a daemon.

-m directory

Look in directory for card device modules. Default is /lib/modules/RELEASE, where RELEASE is the current kernel release.

-o

Configure the cards present in one pass, then exit.

-pfile

Write cardmgr's process ID to file instead of /var/run/cardmgr.pid.

-q

Run in quiet mode. No beeps.

-s file

Write current socket information to file instead of /var/run/stab.

-v

Verbose mode.

-V

Print version number and exit.

cat [options] [files]

Read (concatenate) one or more files and print them on standard output. Read standard input if no files are specified or if - is specified as one of the files; input ends with EOF. You can use the > operator to combine several files into a new file or >> to append files to an existing file.

Options

-A, --show-all

Same as -vET.

-b, --number-nonblank

Number all nonblank output lines, starting with 1.

-e

Same as -vE.

-E, --show-ends

Print $ at the end of each line.

-n, --number

Number all output lines, starting with 1.

-s, --squeeze-blank

Squeeze down multiple blank lines to one blank line.

-t

Same as -vT.

-T, --show-tabs

Print TAB characters as ^I.

-u

Ignored; retained for Unix compatibility.

-v, --show-nonprinting

Display control and nonprinting characters, with the exception of LINEFEED and TAB.

Examples

cat ch1               Display a file
cat ch1 ch2 ch3 > all Combine files
cat note5 >> notes    Append to a file
cat > temp1           Create file at terminal; end with EOF
cat > temp2 << STOP   Create file at terminal; end with STOP

cc [options] files

cdda2wav [options] [output.wav]

Convert Compact Disc Digital Audio (CDDA) to the WAV format. This process is often called "ripping" a CD-ROM, and is generally performed before using an encoder to convert the file to a compressed music format such as OGG or MP3. By default, cdda2wav reads data from the /dev/cdrom device and outputs one WAV file per track.

Options

Some of the following options use sectors as a unit of measurement. Each sector of data on a CD represents approximately 1/75 second of play time.

-D, --device devicename

Specify the device. The device must work with the -i (--interface) settings.

-A , --auxdevice drivename

Specify a different drive for ioctl purposes.

-I, --interface ifname

Specify the type of interface. For Linux systems, the most appropriate value is usually cooked_ioctl.

-s, --stereo

Record in stereo. Use -m (--mono) to record in mono.

-x, --max

Set recording quality (and amount of hard disk usage) to maximum.

-b, --bits-per-sample n

Set the quality of samples to n bits per sample per channel. Possible values are 8, 12, and 16.

-r, --rate n

Set the sample rate in samples per second. To get a list of possible values, use the -R option.

-R, --dump-rates

Output a list of possible sample rates and dividers. This option is typically used alone.

-P, --set-overlap n

Use n sectors of overlap for jitter correction.

-n, --sectors-per-request n

Read n sectors in each request.

-t, --track tracknumber

Set start track and, optionally, end track. Separate the tracks with the + character.

-i, --index n

Set the start index to n when recording.

-o, --offset n

Start recording n sectors before the beginning of the first track.

-O, --output-format

Choose the output file format. Normal file options are wav, aiff, aifc, au, and sun. You can also use cdr and raw for headerless files dumped into recording devices.

-d, --duration

Set to a number followed by f for frames (sectors) or s for seconds. Set time to zero to record an entire track. For example, to copy two minutes, enter 120s.

-B, --bulk

Copy each track into its own file.

-w, --wait

Wait for a signal before recording anything.

-e, --echo

Copy audio data to a sound device rather than to a file.

-p, --set-pitch n

Adjust the pitch by n percent when copying data to an audio device.

-S, --speed-select n

Specify the speed at which your system will read the CD-ROM. Set the value to the multiple of normal playback speed given as your CD-ROM drive speed (4, 16, 32, and so forth). Setting the speed lower than the maximum can prevent errors in some cases.

-q, --quiet

Quiet mode; the program will not send any data to the screen.

-J, --version

Display version and quit.

Examples

For most systems, you should be able to copy a complete CD to a single WAV file with the following command:

cdda2wav

To copy a complete CD to a set of WAV files, one per track:

cdda2wav -B

cdparanoia [options] span [outfile]

Like cdda2wav, cdparanoia records Compact Disc audio files as WAV, AIFF, AIFF-C, or raw format files. It uses additional data-verification and sound-improvement algorithms to make the process more reliable, and is used by a number of graphical recording programs as a backend.

Options

-v, --verbose

Verbose mode.

-q, --quiet

Quiet mode.

-e, --stderr-progress

Send all progress messages to stderr instead of stdout; used by wrapper scripts.

-V, --version

Print version information and quit.

-Q, --query

Display CD-ROM table of contents and quit.

-s, --search-for-drive

Search for a drive, even if /dev/cdrom exists.

-h, --help

Display options and syntax.

-p, --output-raw

Output headerless raw data.

-r, --output-raw-little-endian

Output raw data in little-endian byte order.

-R, --output-raw-big-endian

Output raw data in big-endian byte order.

-w, --output-wav

Output in WAV format. This is the default.

-f, --output-aiff

Output in AIFF format.

-a, --output-aifc

Output in AIFF-C format.

-c, --force-cdrom-little-endian

Force cdparanoia to treat the drive as a little-endian device.

-C, --force-cdrom-big-endian

Force cdparanoia to treat the drive as a big-endian device.

-d, --force-cdrom-device devicename

Specify a device name to use instead of the first readable CD-ROM available.

-S, --force-read-speed n

Set the read speed to n on drives that support it. This is useful if you have a slow drive or are low on memory.

-Z, --disable-paranoia

Disable data verification and correction. Causes cdparanoia to behave exactly as cdda2wav would.

-z, --never-skip[=retries]

If a read fails (for example, due to a scratch in the disc), try again and again. If you specify a number, cdparanoia will try that number of times. If you do not, cdparanoia will retry until it succeeds.

-Y, --disable-extra-paranoia

Use data verification and correction only at read boundaries. Not recommended.

-X, --abort-on-skip

If a read fails and must be skipped, skip the entire track and delete any partially completed output file.

Progress symbols

The output during operation cdparanoia includes both smiley faces and more standard progress symbols. They are:

:-)

Operation proceeding normally.

:-|

Operation proceeding normally, but with jitter during reads.

:-/

Read drift.

8-|

Repeated read problems in the same place.

:-O

SCSI/ATAPI transport error (hardware problem not related to the disc itself).

:-(

Scratch detected.

;-(

Unable to correct problem.

8-X

Unknown and uncorrectable error.

:^D

Finished.

Blank space in the progress indicator means that no corrections were necessary.

-

Jitter correction was required.

+

Read errors.

!

Errors even after correction; repeated read errors.

e

Corrected transport errors.

V

An uncorrected error or a skipped read.

The span argument

The cdparanoia command takes exactly one argument, which describes how much of the CD to record. It uses numbers followed by bracketed times to designate track numbers and time within them. For example, the string 1[2:23]-2[5] indicates a recording from the two-minute and twenty-three-second mark of the first track up to the fifth second of the second track. The time format is demarcated by colons, hours:minutes:seconds:.sectors, with the last item, sectors, preceded by a decimal point (a sector is 1/75 of a second). It's best to put this argument within quotes.

cdrdao command [options] toc-file

Commands

The first argument must be a command. Note that not all options are available for all commands.

show-toc

Print a summary of the CD to be created.

read-toc

Read from a CD and create a disk image and toc file that will allow creation of duplicates.

read-cddb

Check a CDDB server for data about the CD represented by a given toc file, then write that data to the toc file as CD-TEXT data.

show-data

Print out the data that will be written to the CD-R. Useful for checking byte order.

read-test

Check the validity of the audio files described in the toc file.

disk-info

Display information about the CD-R currently in the drive.

msinfo

Display multisession information. Useful mostly for wrapper scripts.

scanbus

Scan the system bus for devices.

simulate

A dry run: do everything except write the CD.

unlock

Unlock the recorder after a failure. Run this command if you cannot eject the CD after using cdrdao.

write

Write the CD.

copy

Copy the CD. If you use a single drive, you will be prompted to insert the CD-R after reading. An image file will be created unless you use the --on-the-fly flag and two CD drives.

Options

cdrecord [general-options] dev=device [track-options] 
track1,track2...

Record data or audio compact discs. This program normally requires root access, and has a large number of options and settings. A number of useful examples can be found in the manpage, which is quite extensive.

General options

General option flags go directly after the cdrecord command. Options affecting the track arguments are placed after the device argument and before the track arguments themselves. The general options are:

--version

Print version information and exit.

-v

Verbose mode. Use one v for each level of verbosity: -vv would be very verbose, and -vvv would be even more so.

-V

As with the -v, a verbose mode counter. However, this applies only to SCSI transport messages. This will slow down the application.

--debug=n, -d

Set the debug level to an integer (greater numbers are more verbose), or use multiple -d flags as with the -v and -V flags.

--kdebug=n, --kd=n

Set the kernel's debug notification value to n during SCSI command execution. Works through the scg-driver.

-s, --silent

Silent mode. Do not print any SCSI error commands.

--force

Override errors if possible. May allow you to blank an otherwise broken CD-RW.

--dummy

Perform a dry run, doing all the steps of recording with the laser turned off. This will let you know whether the process is going to work.

--dao

Disk-at-once mode. Works only with MMC drives that support non-raw session-at-once modes.

--multi

Set to record in multisession mode. Must be present on all sessions but the last one for a multisession disc.

--msinfo

Get multisession information from the CD. Used only with multisession discs onto which you can still record more sessions.

--toc

Display the table of contents for the CD currently in the drive. Works for CD-ROM as well as CD-R and CD-RW drives.

--atip

Display the ATIP (Absolute Time In Pregroove) information for a disc. Only some drives allow you to read this information.

--fix

Close ("fixate") the session, preventing future multisession recordings and allowing the disc to be played in standard audio CD players (some can also play a disc that has not been closed).

--nofix

Do not close the disc after writing.

--load

Load media and exit. Works with tray-loading mechanisms only.

--eject

Eject disc after recording. Some hardware may need to eject a disc after a dummy recording and before the actual recording.

--speed=n

Set the speed to n, a multiple of the audio speed. Normally, cdrecord will get this from the CDR_SPEED environment variable. If your drive has trouble with higher numbers, try 0 as a value.

blank=type

Erase data from a CD-RW in one of the following ways:

help

Display a possible list of blanking methods.

all

Erase all information on the disc. May take a long time.

fast

Perform a quick erase of the disc, erasing only the PMA, TOC, and pregap.

track

Blank a track.

unreserve

Unreserve a track previously marked as reserved.

trtail

Blank the tail of a track only.

unclose

Unclose the last session.

session

Blank the last session.

fs=n

Set the fifo buffer size to n, in bytes. You may use k, m, s, or f to specify kilobytes, megabytes, or units of 2048 and 2352 bytes, respectively. The default is 4MB.

timeout=n

Set the timeout to n seconds. Defaults to 40.

driver=name

Lets you specify a driver for your system. Suggested for experts only. The special drivers cdr_simul and dvd_simul are used for simulation and profiling tests.

driveropts=optlist

Specify a comma-separated list of driver options. To get a list of valid options, use driveropts=help and --checkdrive.

--checkdrive

Check to see if there are valid drivers for the current drive. Returns 0 if the drive is valid.

--scanbus

Scan SCSI devices.

--reset

Attempt to reset the SCSI bus. Does not work on all systems.

--useinfo

Use .inf files to override audio options set elsewhere.

mcn=n

Set the Media Catalog Number to n.

The device argument

The device argument should be specified not as a file but as three integers representing the bus, target, and logical unit, as in the cdrdao command. To check the available options, use the --scanbus option.

Track options and arguments

Track options may be mixed with track arguments, and normally apply to the track immediately after them or to all tracks after them. The track arguments themselves should be the files that you will be writing to the CD. Options are:

cfdisk [options] [device]

System administration command. Partition a hard disk. Normally, device will be /dev/hda, /dev/hdb, /dev/sda, /dev/sdb, /dev/hdc, /dev/hdd, and so on. See also fdisk.

Options

-a

Highlight the current partition with a cursor, not reverse video.

-c cylinders

Specify the number of cylinders.

-g

Ignore driver-provided geometry; guess one instead.

-h heads

Specify the number of heads.

-s sectors

Specify the number of sectors per track.

-v

Print version number and exit.

-z

Do not read the partition table; partition from scratch.

-P format

Display the partition table in format, which must be r (raw data), s (sector order), or t (raw format).

Commands

up arrow, down arrow

Move among partitions.

b

Toggle partition's bootable flag.

d

Delete partition (allow other partitions to use its space).

g

Alter the disk's geometry. Prompt for what to change: cylinders, heads, or sectors (c, h, or s, respectively).

h

Help.

m

Attempt to ensure maximum usage of disk space in the partition.

n

Create a new partition. Prompt for more information.

p

Display the partition table.

q

Quit without saving information.

t

Prompt for a new filesystem type, and change to that type.

u

Change the partition size units, rotating from megabytes to sectors to cylinders and back.

W

Save information.

chage [options] user

Change information about user password expirations. If run without any option flags, chage will prompt for values to be entered; you may also use option flags to change or view information.

Options

-l

This flag is used without any others, and causes chage to display the current password expiration attributes for the user.

-m mindays

Minimum number of days between password changes. Default is zero, meaning that the user may change the password at any time.

-M maxdays

Maximum number of days between password changes.

-d lastday

Date of last password change. This may be expressed as a date in YYYY-MM-DD format, or as the number of days between January 1, 1970 and the last password change.

-I inactive-days

If a password expires and the user does not log in for this number of days, the account will be locked, and the user must contact a system administrator before logging in. Set to 0 to disable the feature.

-E expiredate

Set the date when the account will be locked. This is not a date for password expiration, but for account expiration. It may be expressed as a YYYY-MM-DD date or as a number of days since January 1, 1970.

-W warning

The number of days before password expiration that a user will be warned to change passwords.

chat [options] [script]

System administration command. Set up or initiate dial-up Internet connections; often used in conjunction with pppd, the PPP daemon. On some systems, chat takes the place of the dip program. A chat script is composed of a simple but expressive syntax of paired expect and send strings and sometimes substrings. A script string may contain either text expected from the modem or text to be sent, a chat directive, a substitution character, or a mixture of all three. When reading from a file, lines beginning with # are treated as comments.

Options

-e

Start script with the ECHO directive turned on.

-E

Allow script to read environment variables by using shell $VARIABLE syntax.

-f file

Read chat script from file instead of standard input.

-r file

Send the output of the REPORT directive to file. By default, they are sent to standard error.

-s

Send all error and log information to standard error, even when using the -v option.

-S

Silent mode; send neither error nor log messages to syslogd.

-t n

Set the default timeout value to n seconds. When not specified, the default timeout value is 45 seconds.

-T string

Set the string to be used instead of the \T substitution character. This is usually a phone number.

-U string

Set the string to be used instead of the \U substitution character. This is usually a second phone number.

-v

Verbose mode; log the chat script state and text sent to and received from the modem to syslogd.

-V

Standard error verbose mode; identical to -v, but send information to standard error instead of syslogd.

Chat directives

Scripts are built from paired strings, an expect string and a send string. A null string formed with two single quotes, '', tells chat to expect nothing and just send the send string. A hyphen, -, may be used in an expect string to specify an alternate expect and send in the event the first expect fails. chat will wait, expecting the first part of the string, and if it fails to receive it, it will perform the second part of the string, often a directive. For example:

ogin:-BREAK-ogin:

is interpreted by chat to mean expect the string "ogin:"; if it is not received before the timeout period, send a break signal to the modem, then expect "ogin:" again.

BREAK is an example of a chat directive, which is a special keyword that directs chat to take some action. Most directives are meant for use as expect strings. Some are meant to be special reply strings. BREAK can be used as a reply, or, as the above example shows, can be inserted into an expect substring. The following chat directives are recognized by chat:

ABORT string

If the modem returns the specified string, abort the script. This is often used to capture a modem status sent as a string, such as BUSY or NO CARRIER.

BREAK string

Reply string. Send a break signal to the modem. If the modem returns the specified string, abort the script. This is often used to capture a modem status sent as a string, such as BUSY or NO CARRIER.

CLR_ABORT string

Clear an ABORT string from memory.

CLR_ABORT string

Clear a REPORT string from memory.

ECHO status

Set ECHO to status ON or OFF. When on, chat will echo output from the modem to standard error.

EOT

Reply string. EOT is used as a send string. It instructs chat to send an end-of-file character. This can also be embedded in a string using the character sequence ^D.

REPORT string

When the script receives string, write it and any characters following it to standard error.

HANGUP status

Set HANGUP to status ON or OFF. When on, chat will treat a modem hanging up as an error. When off, it will continue to process the script. You usually want to set this to on after the modem has connected.

SAY string

Print the string to the standard error. This can be used to communicate with the script's user.

TIMEOUT n

Set the timeout value for subsequent expect strings to n seconds.

Substitution characters

''

The null string. When used in place of a send string, chat sends a return character. When used in an expect string, chat expects nothing and just sends the send string.

\b

Backspace character.

\c

Used at the end of a string. Suppresses the newline character automatically added to send strings. Not valid in expect strings.

\d

Pause one second. Not valid in expect strings.

\n

The newline character.

\N, \0

The null character.

\p

Pause one tenth of a second. Not valid in expect strings.

\xd5

Mask this string. Write the string ?????? instead when writing to the system log. Not valid in expect strings.

\r

The carriage return character.

\t

The tab character.

\T

The string specified with the -T option, usually a phone number. Not valid in expect strings.

\U

The string specified with the -U option, usually a second phone number. Not valid in expect strings.

\\

The backslash character.

\ddd

An ASCII character expressed in octal. Not valid in expect strings.

^char

Substitute a control character for char.

@file

Substitute the contents of file. Not valid in expect strings.

$NAME

When using the -E option, substitute the value of the specified environment variable NAME, or substitute nothing if the variable is not set.

Exit codes

checkpc [options]

Options

-a

Don't create missing accounting files specified in :af entries.

-c

Print verbose configuration details.

-D

Run with debugging flags on.

-f

Fix database by creating missing files and changing incorrect file permissions.

-h

Print help message and exit.

-l

Don't create missing logging files specified in :lf entries.

-p

Print information about printcap database.

-r

Remove old job files. Use -A to set the maximum age for job files.

-s

Don't create missing filter status files specified in :ps entries.

-t size[unit]

Truncate log files to specified size. You may specify the unit of that size in k or M for kilobytes or megabytes. The default is megabytes.

-A age[unit]

Report junk or job files older than age. A unit of D, H, M, or S may be used to specify that age represents days, hours, minutes, or seconds. The default is days.

-P printer

Check or fix entries only for the specified printer.

-V

Verbose mode. Report on progress of checkpc including all entries checked and repairs made.

chfn [options] [username]

Options

-f, --full-name

Specify new full name.

-h, --home-phone

Specify new home phone number.

-o, --office

Specify new office number.

-p, --office-phone

Specify new office phone number.

-u, --usage, --help

Print help message and then exit.

-v, --version

Print version information and then exit.

Example

chfn -f "Ellen Siever" ellen

chgrp [options] newgroup files
chgrp [options]

Change the group of one or more files to newgroup. newgroup is either a group ID number or a group name located in /etc/group. Only the owner of a file or a privileged user may change the group.

Options

-c, --changes

Print information about files that are changed.

-f, --silent, --quiet

Do not print error messages about files that cannot be changed.

--help

Print help message and then exit.

-R, --recursive

Traverse subdirectories recursively, applying changes.

--reference=filename

Change the group to that associated with filename. In this case, newgroup is not specified.

-v, --verbose

Verbosely describe ownership changes.

--version

Print version information and then exit.

chmod [options] mode files
chmod [options] --reference=filename files

Change the access mode (permissions) of one or more files. Only the owner of a file or a privileged user may change the mode. mode can be numeric or an expression in the form of who opcode permission. who is optional (if omitted, default is a); choose only one opcode. Multiple modes are separated by commas.

Options

-c, --changes

Print information about files that are changed.

-f, --silent, --quiet

Do not notify user of files that chmod cannot change.

--help

Print help message and then exit.

-R, --recursive

Traverse subdirectories recursively, applying changes.

--reference=filename

Change permissions to match those associated with filename.

-v, --verbose

Print information about each file, whether changed or not.

--version

Print version information and then exit.

Who

u

User.

g

Group.

o

Other.

a

All (default).

Opcode

+

Add permission.

-

Remove permission.

=

Assign permission (and remove permission of the unspecified fields).

Permissions

r

Read.

w

Write.

x

Execute.

s

Set user (or group) ID.

t

Sticky bit; used on directories to prevent removal of files by non-owners.

u

User's present permission.

g

Group's present permission.

o

Other's present permission.

Alternatively, specify permissions by a three-digit octal number. The first digit designates owner permission; the second, group permission; and the third, other's permission. Permissions are calculated by adding the following octal values:

4

Read.

2

Write.

1

Execute.

Note that a fourth digit may precede this sequence. This digit assigns the following modes:

4

Set user ID on execution to grant permissions to process based on the file's owner, not on permissions of the user who created the process.

2

Set group ID on execution to grant permissions to process based on the file's group, not on permissions of the user who created the process.

1

Set sticky bit.

Examples

Add execute-by-user permission to file:

chmod u+x file

Either of the following will assign read/write/execute permission by owner (7), read/execute permission by group (5), and execute-only permission by others (1) to file:

chmod 751 file
chmod u=rwx,g=rx,o=x file

Any one of the following will assign read-only permission to file for everyone:

chmod =r file
chmod 444 file
chmod a-wx,a+r file

The following makes the executable setuid, assigns read/write/execute permission by owner, and assigns read/execute permission by group and others:

chmod 4755 file

chown [options] newowner files
chown [options] --reference=filename files

Change the ownership of one or more files to newowner. newowner is either a user ID number or a login name located in /etc/passwd. chown also accepts users in the form newowner:newgroup or newowner.newgroup. The last two forms change the group ownership as well. If no owner is specified, the owner is unchanged. With a period or colon but no group, the group is changed to that of the new owner. Only the current owner of a file or a privileged user may change the owner.

Options

-c, --changes

Print information about files that are changed.

--dereference

Follow symbolic links.

-f, --silent, --quiet

Do not print error messages about files that cannot be changed.

-h, --no-dereference

Change the ownership of each symbolic link (on systems that allow it) rather than the referenced file.

-v, --verbose

Print information about all files that chown attempts to change, whether or not they are actually changed.

-R, --recursive

Traverse subdirectories recursively, applying changes.

--reference=filename

Change owner to the owner of filename instead of specifying a new owner explicitly.

--help

Print help message and then exit.

--version

Print version information and then exit.

chpasswd [option]

System administration command. Change user passwords in a batch. chpasswd accepts input in the form of one username:password pair per line. If the -e option is not specified, password is encrypted before being stored.

Option

-e

Passwords given are already encrypted.

chroot newroot [command]

System administration command. Change root directory for command or, if none is specified, for a new copy of the user's shell. This command or shell is executed relative to the new root. The meaning of any initial / in pathnames is changed to newroot for a command and any of its children. In addition, the initial working directory is newroot. This command is restricted to privileged users.

chsh [options] [username]

Change your login shell, either interactively or on the command line. Warn if shell does not exist in /etc/shells. Specify the full path to the shell. chsh prompts for your password. Only a privileged user can change another user's shell.

Options

-l, --list-shells

Print valid shells, as listed in /etc/shells, and then exit.

-s shell, --shell shell

Specify new login shell.

-u, --help

Print help message and then exit.

-v, --version

Print version information and then exit.

Example

chsh -s /bin/tcsh

chvt N

cksum [files]

Compute a cyclic redundancy check (CRC) checksum for all files; this is used to ensure that a file was not corrupted during transfer. Read from standard input if the character - or no files are given. Display the resulting checksum, the number of bytes in the file, and (unless reading from standard input) the filename.

clear

Clear the terminal display.

cmp [options] file1 file2 [skip1 [skip2]]

Compare file1 with file2. Use standard input if file1 is - or missing. This command is normally used for comparing binary files, although files can be of any type. (See also comm and diff.) skip1 and skip2 are optional offsets in the files at which the comparison is to start.

Options

-c, --print-chars

Print differing bytes as characters.

-i num, --ignore-initial=num

Ignore the first num bytes of input.

-l, --verbose

Print offsets and codes of all differing bytes.

-s, --quiet, --silent

Work silently; print nothing, but return exit codes:

0

Files are identical.

1

Files are different.

2

Files are inaccessible.

Example

Print a message if two files are the same (exit code is 0):

cmp -s old new && echo 'no changes'

col [options]

A postprocessing filter that handles reverse linefeeds and escape characters, allowing output from tbl or nroff to appear in reasonable form on a terminal.

Options

-b

Ignore backspace characters; helpful when printing manpages.

-f

Process half-line vertical motions, but not reverse line motion. (Normally, half-line input motion is displayed on the next full line.)

-l n

Buffer at least n lines in memory. The default buffer size is 128 lines.

-x

Normally, col saves printing time by converting sequences of spaces to tabs. Use -x to suppress this conversion.

Examples

Run myfile through tbl and nroff, then capture output on screen by filtering through col and more:

tbl myfile | nroff | col | more

Save manpage output for the ls command in out.print, stripping out backspaces (which would otherwise appear as ^H):

man ls | col -b > out.print

colcrt [options] [files]

A postprocessing filter that handles reverse linefeeds and escape characters, allowing output from tbl or nroff to appear in reasonable form on a terminal. Put half-line characters (e.g., subscripts or superscripts) and underlining (changed to dashes) on a new line between output lines.

Options

-

Do not underline.

-2

Double space by printing all half-lines.

column [options] [files]

Format input from one or more files into columns, filling rows first. Read from standard input if no files are specified.

Options

-c num

Format output into num columns.

-s char

Delimit table columns with char. Meaningful only with -t.

-t

Format input into a table. Delimit with whitespace, unless an alternate delimiter has been provided with -s.

-x

Fill columns before filling rows.

comm [options] file1 file2

Compare lines common to the sorted files file1 and file2. Three-column output is produced: lines unique to file1, lines unique to file2, and lines common to both files. comm is similar to diff in that both commands compare two files. But comm can also be used like uniq; comm selects duplicate or unique lines between two sorted files, whereas uniq selects duplicate or unique lines within the same sorted file.

Options

-

Read the standard input.

-num

Suppress printing of column num. Multiple columns may be specified and should not be space-separated.

--help

Print help message and exit.

--version

Print version information and exit.

Example

Compare two lists of top-10 movies, and display items that appear in both lists:

comm -12 siskel_top10 ebert_top10

compress [options] files

Compress one or more files, replacing each with the compressed file of the same name with .Z appended. If no file is specified, compress standard input. Each file specified is compressed separately. compress ignores files that are symbolic links. See also gzip and bzip2, which are more commonly used now.

Options

-b maxbits

Limit the maximum number of bits.

-c

Write output to standard output, not to a .Z file.

-d

Decompress instead of compressing. Same as uncompress.

-f

Force generation of an output file even if one already exists.

-r

If any of the specified files is a directory, compress recursively.

-v

Print compression statistics.

-V

Print version and compilation information and then exit.

cp [options] file1 file2
cp [options] files directory

Copy file1 to file2, or copy one or more files to the same names under directory. If the destination is an existing file, the file is overwritten; if the destination is an existing directory, the file is copied into the directory (the directory is not overwritten).

Options

-a, --archive

Preserve attributes of original files where possible. The same as -dpR.

-b, --backup

Back up files that would otherwise be overwritten.

-d, --no-dereference

Do not dereference symbolic links; preserve hard link relationships between source and copy.

-f, --force

Remove existing files in the destination.

-i, --interactive

Prompt before overwriting destination files.

-l, --link

Make hard links, not copies, of nondirectories.

-p, --preserve

Preserve all information, including owner, group, permissions, and timestamps.

-P, --parents

Preserve intermediate directories in source. The last argument must be the name of an existing directory. For example, the command:

cp --parents jphekman/book/ch1 newdir

copies the file jphekman/book/ch1 to the file newdir/jphekman/book/ch1, creating intermediate directories as necessary.

-r, -R, --recursive

Copy directories recursively.

-S backup-suffix, --suffix=backup-suffix

Set suffix to be appended to backup files. This may also be set with the SIMPLE_BACKUP_SUFFIX environment variable. The default is ~. You need to explicitly include a period if you want one before the suffix (for example, specify .bak, not bak).

-s, --symbolic-link

Make symbolic links instead of copying. Source filenames must be absolute.

-u, --update

Do not copy a file to an existing destination with the same or newer modification time.

-v, --verbose

Before copying, print the name of each file.

-V type, --version-control=type

Set the type of backups made. You may also use the VERSION_CONTROL environment variable. The default is existing. Valid arguments are:

t, numbered

Always make numbered backups.

nil, existing

Make numbered backups of files that already have them; otherwise, make simple backups.

never, simple

Always make simple backups.

-x, --one-file-system

Ignore subdirectories on other filesystems.

Example

Copy the contents of the guest directory recursively into the archives/guest/ directory, and display a message for each file copied:

cd /archives && cp -av /home/guest guest

cpio flags [options]

Copy file archives from or to tape or disk, or to another location on the local machine. Each of the three flags -i, -o, or -p accepts different options.

Flags

-i, --extract [options] [patterns]

Copy in (extract) from an archive files whose names match selected patterns. Each pattern can include Bourne shell filename metacharacters. (Patterns should be quoted or escaped so that they are interpreted by cpio, not by the shell.) If pattern is omitted, all files are copied in. Existing files are not overwritten by older versions from the archive unless -u is specified.

-o, --create [options]

Copy out to an archive a list of files whose names are given on the standard input.

-p, --pass-through [options] directory

Copy (pass) files to another directory on the same system. Destination pathnames are interpreted relative to the named directory.

Comparison of valid options

Options available to the -i, -o, and -p flags are shown here (the - is omitted for clarity):

i:   bcdf mnrtsuv B SVCEHMR IF
o: 0a c         vABL VC HM O F
p: 0a  d lm    uv  L V    R

Options

-0, --null

Expect list of filenames to be terminated with null, not newline. This allows files with a newline in their names to be included.

-a, --reset-access-time

Reset access times of input files after reading them.

-A, --append

Append files to an existing archive, which must be a disk file. Specify this archive with -O or -F.

-b, --swap

Swap bytes and half-words to convert between big-endian and little-endian 32-bit integers.

-B

Block input or output using 5120 bytes per record (default is 512 bytes per record).

--blocksize=size

Set input or output blocksize to size × 512 bytes.

-c

Read or write header information as ASCII characters; useful when source and destination machines are different types.

-C n, --io-size=n

Like -B, but blocksize can be any positive integer n.

-d, --make-directories

Create directories as needed.

-E file, --pattern-file=file

Extract from the archives filenames that match patterns in file.

-f, --nonmatching

Reverse the sense of copying; copy all files except those that match patterns.

-F file, --file=file

Use file as the archive, not stdin or stdout. file can reside on another machine, if given in the form user@hostname:file (where user@ is optional).

--force-local

Assume that file (provided by -F, -I, or -O) is a local file, even if it contains a colon (:) indicating a remote file.

-H type, --format=type

Use type format. Default for copy-out is bin; default for copy-in is autodetection of the format. Valid formats (all caps also accepted) are:

bin

Binary.

odc

Old (POSIX.1) portable format.

newc

New (SVR4) portable format.

crc

New (SVR4) portable format with checksum added.

tar

Tar.

ustar

POSIX.1 tar (also recognizes GNU tar archives).

hpbin

HP-UX's binary (obsolete).

hpodc

HP-UX's portable format.

-I file

Read file as an input archive. May be on a remote machine (see -F).

-k

Ignored. For backward compatibility.

-l, --link

Link files instead of copying.

-L, --dereference

Follow symbolic links.

-m, --preserve-modification-time

Retain previous file modification time.

-M msg, --message=msg

Print msg when switching media, as a prompt before switching to new media. Use variable %d in the message as a numeric ID for the next medium. -M is valid only with -I or -O.

-n, --numeric-uid-gid

When verbosely listing contents, show user ID and group ID numerically.

--no-absolute-filenames

Create all copied-in files relative to the current directory.

--no-preserve-owner

Make all copied files owned by yourself, instead of the owner of the original. Can be used only if you are a privileged user.

-O file

Archive the output to file, which may be a file on another machine (see -F).

--only-verify-crc

For a CRC-format archive, verify the CRC of each file; don't actually copy the files in.

--quiet

Don't print the number of blocks copied.

-r

Rename files interactively.

-R [user][:group], --owner [user][:group]

Reassign file ownership and group information to the user's login ID (privileged users only).

-s, --swap-bytes

Swap bytes of each two-byte half-word.

-S, --swap-half-words

Swap half-words of each four-byte word.

--sparse

For copy-out and copy-pass, write files that have large blocks of zeros as sparse files.

-t, --list

Print a table of contents of the input (create no files). When used with the -v option, resembles output of ls -l.

-u, --unconditional

Unconditional copy; old files can overwrite new ones.

-v, --verbose

Print a list of filenames processed.

-V, --dot

Print a dot for each file read or written (this shows cpio at work without cluttering the screen).

--version

Print version number and then exit.

Examples

Generate a list of files whose names end in .old using find; use the list as input to cpio:

find . -name "*.old" -print | cpio -ocBv > /dev/rst8

Restore from a tape drive all files whose names contain save (subdirectories are created if needed):

cpio -icdv "*save*" < /dev/rst8

Move a directory tree:

find . -depth -print | cpio -padm /mydir

cpp [options] [ ifile [ ofile ] ]

GNU C language preprocessor. cpp is normally invoked as the first pass of any C compilation by the gcc command. The output of cpp is a form acceptable as input to the next pass of the C compiler. The ifile and ofile options are, respectively, the input and output for the preprocessor; they default to standard input and standard output.

Options

-$

Do not allow $ in identifiers.

-ansi

Use 1990 ISO C standard. This is equivalent to -std=c89.

-dD

Similar to -dM, but exclude predefined macros and include results of preprocessing.

-dM

Suppress normal output. Print series of #defines that create the macros used in the source file.

-dN

Similar to -dD, but don't print macro expansions.

-dI

Print #include directives in addition to other output.

-fpreprocessed

Treat file as already preprocessed. Skip most processing directives, remove all comments, and tokenize file.

-ftabstop=width

Set distance between tabstops so columns will be reported correctly in warnings and errors. Default is 8.

-fno-show-column

Omit column numbers in warnings and errors.

-gcc

Define _ _GNUC_ _, _ _GNUC_MINOR_ _, and _ _GNUC_PATCHLEVEL_ _ macros.

--help

Print usage message and exit.

-idirafter dir

Search dir for header files when a header file is not found in any of the included directories.

-imacros file

Process macros in file before processing main files.

-include file

Process file before main file.

-iprefix prefix

When adding directories with -iwithprefix, prepend prefix to the directory's name.

-isystem dir

Search dir for header files after searching directories specified with -I but before searching standard system directories.

-iwithprefix dir

Append dir to the list of directories to be searched when a header file cannot be found in the main include path. If -iprefix has been set, prepend that prefix to the directory's name.

-iwithprefixbefore dir

Insert dir at the beginning of the list of directories to be searched when a header file cannot be found in the main include path. If -iprefix has been set, prepend that prefix to the directory's name.

-lang-c, -lang-c++, -lang-objc, -lang-objc++

Expect the source to be in C, C++, Objective C, or Objective C++, respectively.

-lint

Display all lint commands in comments as #pragma lint command.

-nostdinc

Search only specified, not standard, directories for header files.

-nostdinc++

Suppress searching of directories believed to contain C++-specific header files.

-o file

Write output to file. (Same as specifying a second filename in the command line.)

-pedantic

Warn verbosely.

-pedantic-errors

Produce a fatal error in every case in which -pedantic would have produced a warning.

-std=standard

Specify C standard of input file. Accepted values are:

iso9899:1990, c89

1990 ISO C standard.

iso9899:199409

1994 amendment to the 1990 ISO C standard.

iso9899:1999, c99, iso9899:199x, c9x

1999 revised ISO C standard.

gnu89

1990 C Standard with gnu extensions. The default value.

gnu99, gnu9x

1999 revised ISO C standard with gnu extensions.

-traditional

Behave like traditional C, not ANSI.

-trigraphs

Convert special three-letter sequences, meant to represent missing characters on some terminals, into the single character they represent.

-undef

Suppress definition of all nonstandard macros.

-v

Verbose mode.

-version

Print version number, then process file.

--version

Print version number then exit.

-w

Don't print warnings.

-x language

Specify the language of the input file. language may be c, c++, objective-c, or assembler-with-cpp. By default, language is deduced from the filename extension. If the extension is unrecognized, the default is c.

-A name[=def]

Assert name with value def as if defined by #assert. To turn off standard assertions, use -A-.

-A -name[=def]

Cancel assertion name with value def.

-C

Retain all comments except those found on cpp directive lines. By default, cpp strips C-style comments.

-Dname[=def]

Define name with value def as if by a #define. If no =def is given, name is defined with value 1. -D has lower precedence than -U.

-E

Preprocess the source files, but do not compile. Print result to standard output. This option is usually passed from gcc.

-H

Print pathnames of included files, one per line, on standard error.

-Idir

Search in directory dir for #include files whose names do not begin with / before looking in directories on standard list. #include files whose names are enclosed in double quotes and do not begin with / will be searched for first in the current directory, then in directories named on -I options, and last in directories on the standard list.

-I-

Split includes. Search directories specified by -I options preceding this one for header files included with quotes (#include "file.h") but not for header files included with angle brackets (#include <file.h>). Search directories specified by -I options following this one for all header files.

-M [-MG]

Suppress normal output. Print a rule for make that describes the main source file's dependencies. If -MG is specified, assume that missing header files are actually generated files, and look for them in the source file's directory.

-MF file

Print rules generated by -M or -MM to file.

-MD file

Similar to -M, but output to file; also compile the source.

-MM

Similar to -M, but describe only those files included as a result of #include "file".

-MMD file

Similar to -MD, but describe only the user's header files.

-MQ target

Similar to -MT, but quote any characters that are special to make.

-MT target

Specify the target to use when generating a rule for make. By default the target is based on the name of the main input file.

-P

Preprocess input without producing line-control information used by next pass of the C compiler.

-Uname

Remove any initial definition of name, where name is a reserved symbol predefined by the preprocessor or a name defined on a -D option. Names predefined by cpp are unix and i386 (for Intel systems).

-Wall

Warn both on nested comments and trigraphs.

-Wcomment, -Wcomments

Warn when encountering the beginning of a nested comment.

-Wtraditional

Warn when encountering constructs that are interpreted differently in ANSI than in traditional C.

-Wtrigraph, -Wcomments

Warn when encountering trigraphs, three-letter sequences meant to represent missing characters on some terminals.

Special names

cpp understands various special names, some of which are:

_ _DATE_ _

Current date (e.g., Jan 10 2003).

_ _FILE_ _

Current filename (as a C string).

_ _LINE_ _

Current source line number (as a decimal integer).

_ _TIME_ _

Current time (e.g., 12:00:00).

These special names can be used anywhere, including in macros, just like any other defined names. cpp's understanding of the line number and filename may be changed using a #line directive.

Directives

All cpp directive lines start with # in column 1. Any number of blanks and tabs is allowed between the # and the directive. The directives are: