.TH SH-ARG 1
.SH NAME
arg \- shell command-line argument parsing
.SH SYNOPSIS
.B load arg
.br
.B arg
[
.I opts command
]...
.B -
.I args
.SH DESCRIPTION
.I Arg
is a loadable module for
.IR sh (1)
that parses command-line arguments in the same
form as
.IR arg (2).
It accepts a list of
.RI ( opts ,\  command )
pairs, where
each character in
.I opts
is an acceptable option, and
.I command
is a shell command to be run if any character
in
.I opts
is found.
If the last character in
.I opts
is a plus
.RB ( + ),
then
.I arg
will extract the argument associated with the option
before running
.IR command .
For the duration of
.IR command ,
the environment variable
.B $opt
will be set to the option that has been found,
and 
.B $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
.RB ( * )
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
.B usage
exception raised.
.PP
The list of option specifications is terminated with a single
minus
.RB ( - );
the arguments to be parsed follow this.
When the argument parsing has finished
the environment variable
.B $args
is set to the remaining list of arguments.
.SH EXAMPLE
The following shell script,
.BR script ,
takes options
.BR b ,
.B c
and
.BR f ,
where
.B f
takes a file name argument.
.EX
#!/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
.EE
.PP
When invoked as follows:
.IP
.B "script -bc -ffile a b c"
.PP
the output is:
.IP
.EX
\&./script 1 1 file
arguments are a b c
.EE
.PP
and when invoked by:
.IP
.B "script -b -f file -z -- -bc"
.PP
the output is:
.IP
.EX
unknown option z
\&./script 1 0 file
arguments are -bc
.EE
.SH SOURCE
.B /appl/cmd/sh/arg.b
.SH SEE ALSO
.IR sh (1),
.IR arg (2),
.IR sh-std (1)