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.TH GETSUBOPT 3C "Sep 29, 2005"
.SH NAME
getsubopt \- parse suboption arguments from a string
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBgetsubopt\fR(\fBchar **\fR\fIoptionp\fR, \fBchar * const *\fR\fIkeylistp\fR, \fBchar **\fR\fIvaluep\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBgetsubopt()\fR function parses suboption arguments in a flag argument.
Such options often result from the use of \fBgetopt\fR(3C).
.sp
.LP
The \fBgetsubopt()\fR argument \fIoptionp\fR is a pointer to a pointer to the
option argument string. The suboption arguments are separated by commas and
each can consist of either a single token or a token-value pair separated by an
equal sign.
.sp
.LP
The \fIkeylistp\fR argument is a pointer to a vector of strings. The end of the
vector is identified by a null pointer. Each entry in the vector is one of the
possible tokens that might be found in *\fIoptionp\fR. Since commas delimit
suboption arguments in \fIoptionp\fR, they should not appear in any of the
strings pointed to by \fIkeylistp\fR. Similarly, because an equal sign
separates a token from its value, the application should not include an equal
sign in any of the strings pointed to by \fIkeylistp\fR.
.sp
.LP
The \fIvaluep\fR argument is the address of a value string pointer.
.sp
.LP
If a comma appears in \fIoptionp\fR, it is interpreted as a suboption
separator. After commas have been processed, if there are one or more equal
signs in a suboption string, the first equal sign in any suboption string is
interpreted as a separator between a token and a value. Subsequent equal signs
in a suboption string are interpreted as part of the value.
.sp
.LP
If the string at *\fIoptionp\fR contains only one suboption argument
(equivalently, no commas), \fBgetsubopt()\fR updates *\fIoptionp\fR to point to
the null character at the end of the string. Otherwise, it isolates the
suboption argument by replacing the comma separator with a null character and
updates *\fIoptionp\fR to point to the start of the next suboption argument. If
the suboption argument has an associated value (equivalently, contains an equal
sign), \fBgetsubopt()\fR updates *\fIvaluep\fR to point to the value's first
character. Otherwise, it sets *\fIvaluep\fR to a null pointer. The calling
application can use this information to determine whether the presence or
absence of a value for the suboption is an error.
.sp
.LP
Additionally, when \fBgetsubopt()\fR fails to match the suboption with a token
in the \fIkeylistp\fR array, the calling application should decide if this is
an error or if the unrecognized option should be processed in another way.
.SH RETURN VALUES
.sp
.LP
The \fBgetsubopt()\fR function returns the index of the matched token string or
-1 if no token strings were matched.
.SH ERRORS
.sp
.LP
No errors are defined.
.SH EXAMPLES
.LP
\fBExample 1 \fRUse \fBgetsubopt()\fR to process options.
.sp
.LP
The following example demonstrates the processing of options to the
\fBmount\fR(8) utility using \fBgetsubopt()\fR.

.sp
.in +2
.nf
#include <stdlib.h>

char *myopts[] = {
#define READONLY     0
            "ro",
#define READWRITE    1
            "rw",
#define WRITESIZE    2
            "wsize",
#define READSIZE     3
            "rsize",
            NULL};

main(argc, argv)
    int  argc;
    char **argv;
{
    int sc, c, errflag;
    char *options, *value;
    extern char *optarg;
    extern int optind;
    .
    .
    .
    while((c = getopt(argc, argv, "abf:o:")) != -1) {
        switch (c) {
        case 'a': /* process a option */
            break;
        case 'b': /* process b option */
            break;
        case 'f':
            ofile = optarg;
            break;
        case '?':
            errflag++;
            break;
        case 'o':
            options = optarg;
            while (*options != '\e0') {
                switch(getsubopt(&options,myopts,&value)){
                case READONLY : /* process ro option */
                    break;
                case READWRITE : /* process rw option */
                    break;
                case WRITESIZE : /* process wsize option */
                    if (value == NULL) {
                        error_no_arg();
                        errflag++;
                    } else
                        write_size = atoi(value);
                    break;
                case READSIZE : /* process rsize option */
                    if (value == NULL) {
                        error_no_arg();
                        errflag++;
                    } else
                        read_size = atoi(value);
                    break;
                default :
                    /* process unknown token */
                    error_bad_token(value);
                    errflag++;
                    break;
                   }
            }
              break;
        }
    }
    if (errflag) {
        /* print usage instructions etc. */
    }
    for (; optind<argc; optind++) {
        /* process remaining arguments */
    }
    .
    .
    .
}
.fi
.in -2

.LP
\fBExample 2 \fRParse suboptions.
.sp
.LP
The following example uses the \fBgetsubopt()\fR function to parse a value
argument in the \fIoptarg\fR external variable returned by a call to
\fBgetopt\fR(3C).

.sp
.in +2
.nf
#include <stdlib.h>
\&...
char *tokens[] = {"HOME", "PATH", "LOGNAME", (char *) NULL };
char *value;
int opt, index;
while ((opt = getopt(argc, argv, "e:")) != -1) {
    switch(opt) {
    case 'e' :
        while ((index = getsubopt(&optarg, tokens, &value)) != -1) {
            switch(index) {
\&...
        }
        break;
\&...
    }
}
.fi
.in -2

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR getopt (3C),
.BR attributes (7),
.BR standards (7),
.BR mount (8)