SH-ARG(1) SH-ARG(1)
NAME
arg - shell command-line argument parsing
SYNOPSIS
load arg
arg [ opts command ]... - args
DESCRIPTION
Arg is a loadable module for sh(1) that parses command-line
arguments in the same form as arg(2). It accepts a list of
(opts, command) pairs, where each character in opts is an
acceptable option, and command is a shell command to be run
if any character in opts is found. If the last character in
opts is a plus (+), then arg will extract the argument asso-
ciated with the option before running command. For the dura-
tion of command, the environment variable $opt will be set
to the option that has been found, and $arg will be set to
the option's argument (if the argument has been extracted
and there is such an argument, otherwise it will be set to
nil). The option character asterisk (*) matches any option
letter (this must be quoted, to avoid the usual special
interpretation by the shell). Only one command will be run
for any option found; if there is no matching option letter,
then a default error message will be printed, and a usage
exception raised.
The list of option specifications is terminated with a sin-
gle minus (-); the arguments to be parsed follow this. When
the argument parsing has finished the environment variable
$args is set to the remaining list of arguments.
EXAMPLE
The following shell script, script, takes options b, c and
f, where f takes a file name argument.
#!/dis/sh
load arg
bflag := cflag := 0
file := ()
args := $*
(arg
bc {$opt^flag = 1}
f+ {file=$arg}
'*' {echo unknown option $opt}
- $args
)
echo $0 $bflag $cflag $file
echo arguments are $args
When invoked as follows:
Page 1 Plan 9 (printed 12/22/24)
SH-ARG(1) SH-ARG(1)
script -bc -ffile a b c
the output is:
./script 1 1 file
arguments are a b c
and when invoked by:
script -b -f file -z -- -bc
the output is:
unknown option z
./script 1 0 file
arguments are -bc
SOURCE
/appl/cmd/sh/arg.b
SEE ALSO
sh(1), arg(2), sh-std(1)
Page 2 Plan 9 (printed 12/22/24)