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3.4. Common Features

The following table displays features that are common to the Bourne, Korn, and C shells. Note that the Korn shell is an enhanced version of the Bourne shell; therefore, the Korn shell includes all features of the Bourne shell, plus some others. The commands bg, fg, jobs, stop, and suspend are available only on systems that support job control. (Essentially all modern Unix systems do.)

>Redirect output.
>>Append to file.
<Redirect input.
<<“Here” document (redirect input).
|Pipe output.
|&Start a coprocess. Korn shell only.
&Run process in background.
;Separate commands on same line.
*Match any character(s) in filename.
?Match single character in filename.
[ ]Match any characters enclosed.
( )Execute in subshell.
‘ ‘Substitute output of enclosed command.
" "Partial quote (allows variable and command expansion).
' 'Full quote (no expansion).
\Quote following character.
$varUse value for variable.
$$Process ID.
$0Command name.
$nnth argument (0 Figure n Figure 9).
$*All arguments as simple words.
#Begin comment.
bgBackground execution.
breakBreak from loop statements.
cdChange directory.
continueResume a program loop.
echoDisplay output.
evalEvaluate arguments.
execExecute a new shell.
fgForeground execution.
jobsShow active jobs.
killTerminate running jobs.
shiftShift positional parameters.
stopSuspend a background job.
suspendSuspend a foreground job (such as a shell created by su).
timeTime a command.
umaskSet default file permissions for new files.
unsetErase variable or function definitions.
waitWait for a background job to finish.

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