Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/std_unix/mod.std.unix.v1/text0008.txt

Internet Message Format | 1987-06-30 | 9.5 KB

From: John Quarterman (moderator) <ut-sally!std-unix>

Topic: yet more on getopt (command line arguments)

Two more messages, the first a followup to a previous posting, and
the second public domain sources and man pages for getopt(3) and getopt(1).
    -mod

----------------------------------------------------------------------

From: ihnp4!utzoo!henry
Date: 3 Jul 85 18:34:41 CDT (Wed)
To: ihnp4!ut-sally!std-unix
Subject: Re: command line arguments

> > A group of bundled options may end with an option that has an argument.
>
> This creates confusion in using C-Kermit when you want to send an image
> file.  For example:
>
>     send -is filename     < ---  works fine
>         send -si filename     < ---  bombs the program

The AT&T syntax standard (which getopt does not completely enforce)
actually forbids both of these usages.  Options with arguments are not
allowed to be bundled, and they must be separated from their arguments
by a space.

> I would *much* prefer to bundle the flags, then
> have those with arguments pick them up in the same order as the flags are
> listed.

The few existing commands that use such a convention, notably tar(1), are
(in my experience) the worse for it.  It's seriously error-prone.  I think
the AT&T people did the right thing.

------------------------------

Date: Tue, 2 Jul 85 13:07:09 edt
From: ihnp4!utcs!ian (Ian F. Darwin)
To: ihnp4!ut-sally![e-mail]
Subject: here is getopt

Here is the source for getopt(3), the function that should be in
everybody's C program, and getopt(1), a program that uses it to
make shell programs comprehensible and consistent. There are man
pages for both. Please send these on to the mod. group. Thanks.

[ I have hacked the following shell script slightly so that
it doesn't extract directly into system source directories,
rather into the current directory.  It should be assumed that
this code comes with no warranty from me, Ian Darwin, or anyone
else as to whether it accurately represents getopt as distributed
with System V, or any command line standard, or that it works
at all, or that it will cause no damage when extracted or used. -mod]

#! /bin/sh
#! To unbundle, sh this file
echo x - "(/usr/man/man3/getopt.3)" >&2
echo x - mkdir lib >&2
mkdir lib >&2
echo x - lib/getopt.3 >&2
cat >lib/getopt.3 <<"//SYSIN DD SYSOUT=BD"
.TH GETOPT 3 local
.DA 25 March 1982
.SH NAME
getopt \- get option letter from argv
.SH SYNOPSIS
.ft B
int getopt(argc, argv, optstring)
.br
int argc;
.br
char **argv;
.br
char *optstring;
.sp
extern char *optarg;
.br
extern int optind;
.ft
.SH DESCRIPTION
.I Getopt
returns the next option letter in
.I argv
that matches a letter in
.IR optstring .
.I Optstring
is a string of recognized option letters;
if a letter is followed by a colon, the option is expected to have
an argument that may or may not be separated from it by white space.
.I Optarg
is set to point to the start of the option argument on return from
.IR getopt .
.PP
.I Getopt
places in
.I optind
the
.I argv
index of the next argument to be processed.
Because
.I optind
is external, it is normally initialized to zero automatically
before the first call to
.IR getopt .
.PP
When all options have been processed (i.e., up to the first
non-option argument),
.I getopt
returns
.BR EOF .
The special option
.B \-\-
may be used to delimit the end of the options;
.B EOF
will be returned, and
.B \-\-
will be skipped.
.SH SEE ALSO
getopt(1)
.SH DIAGNOSTICS
.I Getopt
prints an error message on
.I stderr
and returns a question mark
.RB ( ? )
when it encounters an option letter not included in
.IR optstring .
.SH EXAMPLE
The following code fragment shows how one might process the arguments
for a command that can take the mutually exclusive options
.B a
and
.BR b ,
and the options
.B f
and
.BR o ,
both of which require arguments:
.PP
.RS
.nf
main(argc, argv)
int argc;
char **argv;
{
    int c;
    extern int optind;
    extern char *optarg;
    \&.
    \&.
    \&.
    while ((c = getopt(argc, argv, "abf:o:")) != EOF)
        switch (c) {
        case 'a':
            if (bflg)
                errflg++;
            else
                aflg++;
            break;
        case 'b':
            if (aflg)
                errflg++;
            else
                bproc();
            break;
        case 'f':
            ifile = optarg;
            break;
        case 'o':
            ofile = optarg;
            break;
        case '?':
        default:
            errflg++;
            break;
        }
    if (errflg) {
        fprintf(stderr, "Usage: ...");
        exit(2);
    }
    for (; optind < argc; optind++) {
        \&.
        \&.
        \&.
    }
    \&.
    \&.
    \&.
}
.RE
.PP
A template similar to this can be found in
.IR /usr/pub/template.c .
.SH HISTORY
Written by Henry Spencer, working from a Bell Labs manual page.
Behavior believed identical to the Bell version.
.SH BUGS
It is not obvious how
`\-'
standing alone should be treated;  this version treats it as
a non-option argument, which is not always right.
.PP
Option arguments are allowed to begin with `\-';
this is reasonable but reduces the amount of error checking possible.
.PP
.I Getopt
is quite flexible but the obvious price must be paid:  there is much
it could do that it doesn't, like
checking mutually exclusive options, checking type of
option arguments, etc.
//SYSIN DD SYSOUT=BD
echo x - "(/usr/man/man1/getopt.1)" >&2
echo x - mkdir bin >&2
mkdir bin >&2
echo x - bin/getopt.1 >&2
cat >bin/getopt.1 <<"//SYSIN DD SYSOUT=BD"
.TH GETOPT 1 local
.DA 12 April 1984
.SH NAME
getopt \- parse command options
.SH SYNOPSIS
.B set \-\- \`getopt
optstring
.B $*\`
.SH DESCRIPTION
.I Getopt
is used to break up options in command lines for easy parsing by
shell procedures, and to check for legal options.
.I Optstring
is a string of recognized option letters (see
.IR getopt (3));
if a letter is followed by a colon, the option
is expected to have an argument which may or may not be
separated from it by white space.
The special option
.B \-\-
is used to delimit the end of the options.
.I Getopt
will place
.B \-\-
in the arguments at the end of the options,
or recognize it if used explicitly.
The shell arguments
(\fB$1 $2\fR ...) are reset so that each option is
preceded by a
.B \-
and in its own shell argument;
each option argument is also in its own shell argument.
.SH EXAMPLE
The following code fragment shows how one might process the arguments
for a command that can take the options
.B a
and
.BR b ,
and the option
.BR o ,
which requires an argument.
.PP
.RS
.nf
set \-\- \`getopt abo: $*\`
if test $? != 0
then
    echo 'Usage: ...'
    exit 2
fi
for i
do
    case "$i"
    in
        \-a|\-b)
            flag=$i; shift;;
        \-o)
            oarg=$2; shift; shift;;
        \-\-)
            shift; break;;
    esac
done
.fi
.RE
.PP
This code will accept any of the following as equivalent:
.PP
.RS
.nf
cmd \-aoarg file file
cmd \-a \-o arg file file
cmd \-oarg -a file file
cmd \-a \-oarg \-\- file file
.RE
.PP
A program template similar to this example can be found in
.IR /usr/pub/template.sh .
.SH SEE ALSO
sh(1), getopt(3)
.SH DIAGNOSTICS
.I Getopt
prints an error message on the standard error output when it
encounters an option letter not included in
.IR optstring .
.SH HISTORY
Written by Henry Spencer, working from a Bell Labs manual page.
Behavior believed identical to the Bell version.
.SH BUGS
Whatever
.IR getopt (3)
has.
.PP
Arguments containing white space or imbedded shell metacharacters
generally will not survive intact;  this looks easy to fix but isn't.
.PP
The error message for an invalid option is identified as coming
from
.I getopt
rather than from the shell procedure containing the invocation
of
.IR getopt ;
this again is hard to fix.
.PP
The precise best way to use the
.I set
command to set the arguments without disrupting the value(s) of
shell options varies from one shell version to another.
//SYSIN DD SYSOUT=BD
echo x - "(/usr/src/lib/libc/gen/getopt.c)" >&2
echo x - lib/getopt.c >&2
cat >lib/getopt.c <<"//SYSIN DD SYSOUT=BD"
/*
 * getopt - get option letter from argv
 */

#include <stdio.h>

char    *optarg;    /* Global argument pointer. */
int    optind = 0;    /* Global argv index. */

static char    *scan = NULL;    /* Private scan pointer. */

extern char    *index();

int
getopt(argc, argv, optstring)
int argc;
char *argv[];
char *optstring;
{
    register char c;
    register char *place;

    optarg = NULL;

    if (scan == NULL || *scan == '\0') {
        if (optind == 0)
            optind++;

        if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
            return(EOF);
        if (strcmp(argv[optind], "--")==0) {
            optind++;
            return(EOF);
        }

        scan = argv[optind]+1;
        optind++;
    }

    c = *scan++;
    place = index(optstring, c);

    if (place == NULL || c == ':') {
        fprintf(stderr, "%s: unknown option -%c\n", argv[0], c);
        return('?');
    }

    place++;
    if (*place == ':') {
        if (*scan != '\0') {
            optarg = scan;
            scan = NULL;
        } else if (optind < argc) {
            optarg = argv[optind];
            optind++;
        } else {
            fprintf(stderr, "%s: -%c argument missing\n", argv[0], c);
            return('?');
        }
    }

    return(c);
}
//SYSIN DD SYSOUT=BD
echo x - "(/usr/src/bin/getopt.c)" >&2
echo x - bin/getopt.c >&2
cat >bin/getopt.c <<"//SYSIN DD SYSOUT=BD"
#include <stdio.h>

main(argc, argv)
int argc;
char *argv[];
{
    extern int optind;
    extern char *optarg;
    int c;
    int status = 0;

    optind = 2;    /* Past the program name and the option letters. */
    while ((c = getopt(argc, argv, argv[1])) != EOF)
        switch (c) {
        case '?':
            status = 1;    /* getopt routine gave message */
            break;
        default:
            if (optarg != NULL)
                printf(" -%c %s", c, optarg);
            else
                printf(" -%c", c);
            break;
        }
    printf(" --");
    for (; optind < argc; optind++)
        printf(" %s", argv[optind]);
    printf("\n");
    exit(status);
}
//SYSIN DD SYSOUT=BD
exit 0

----------------------------------------------------------------------
--

John Quarterman, [e-mail], {ihnp4,seismo,ctvax}!ut-sally!jsq

Volume-Number: Volume 1, Number 09