[Most of this article, except
, also applies to the
C shell. -JP]
The Bourne shell command line can have options like
any command returns non-zero status).
It can also have other arguments; these are passed to shell scripts.
You can set new command-line parameters while you're typing interactive
commands (at a shell prompt) or in a shell script.
To reset the command-line parameters, just type
followed by the new
So, for example, to ask the shell to show expanded versions of command lines
after you type them, set the
(verbose) option (
mail $group1 < message
mail andy ellen heather steve wilma < message
mail $group2 < message
mail firstname.lastname@example.org email@example.com firstname.lastname@example.org < message
option on many Bourne shells.
You can put filenames or any other strings in the command-line parameters
interactively or from a shell script.
That's handy for storing and parsing the output of a UNIX command with
For example, you can get a list of all logged-in users from the parameters
, and so on.
if your system has it.
to strip off everything but the
set `who | cut -c1-8`
...do something with each user ($u)...
You can save the original parameters in another variable and reset them
...use new settings...
If the first parameter you
starts with a dash, like
the shell will treat it as its own option instead of as a string to
put into the command-line parameters.
To avoid this, use
(two dashes) as the first argument to
In this example,
, and the filenames expanded
from the wildcard pattern go into
set -- -e file*
Because the shell parses and scans the new parameters before it stores them,
special characters (
will be interpreted - watch your
You can take advantage of this to parse lines of text into pieces that
aren't separated with the usual spaces and TABs - for instance, a line from a
database with colon-separated
fields - by setting the
variable before the
If you want to save any special quoting on the original command line,
be careful; the quoting will be lost unless you're clever.
For example, if
used to be
it'll be split
after it's restored:
solution might be to use a
for the part of the script where you need to reset the command-line
# reset command-line parameters during subshell only:
some new parameters
do something with new parameters
# original parameters aren't affected from here on...
One last note:
, the name of the script file.