man-pages/man3p/getsubopt.3p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "GETSUBOPT" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" getsubopt 
.SH NAME
getsubopt \- parse suboption arguments from a string
.SH SYNOPSIS
.LP
\fB#include <stdlib.h>
.br
.sp
int getsubopt(char **\fP\fIoptionp\fP\fB, char * const *\fP\fIkeylistp\fP\fB,
char **\fP\fIvaluep\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIgetsubopt\fP() function shall parse suboption arguments in
a flag argument. Such options often result from the use of \fIgetopt\fP().
.LP
The \fIgetsubopt\fP() argument \fIoptionp\fP is a pointer to a pointer
to the option argument string. The suboption arguments
shall be separated by commas and each may consist of either a single
token, or a token-value pair separated by an equal sign.
.LP
The \fIkeylistp\fP argument shall be 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\fP. Since commas delimit suboption
arguments in \fIoptionp\fP, they should not appear in any of the strings
pointed to by \fIkeylistp\fP. 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\fP.
.LP
The \fIvaluep\fP argument is the address of a value string pointer.
.LP
If a comma appears in \fIoptionp\fP, it shall be 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 shall be interpreted as a
separator between a token and a value. Subsequent equal signs in a
suboption string shall be interpreted as part of the value.
.LP
If the string at *\fIoptionp\fP contains only one suboption argument
(equivalently, no commas), \fIgetsubopt\fP() shall update
*\fIoptionp\fP to point to the null character at the end of the string.
Otherwise, it shall isolate the suboption argument by
replacing the comma separator with a null character, and shall update
*\fIoptionp\fP to point to the start of the next suboption
argument. If the suboption argument has an associated value (equivalently,
contains an equal sign), \fIgetsubopt\fP() shall update
*\fIvaluep\fP to point to the value's first character. Otherwise,
it shall set *\fIvaluep\fP to a null pointer. The calling
application may use this information to determine whether the presence
or absence of a value for the suboption is an error.
.LP
Additionally, when \fIgetsubopt\fP() fails to match the suboption
argument with a token in the \fIkeylistp\fP array, the
calling application should decide if this is an error, or if the unrecognized
option should be processed in another way.
.SH RETURN VALUE
.LP
The \fIgetsubopt\fP() function shall return the index of the matched
token string, or -1 if no token strings were matched.
.SH ERRORS
.LP
No errors are defined.
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.sp
.RS
.nf

\fB#include <stdio.h>
#include <stdlib.h>
.sp

int do_all;
const char *type;
int read_size;
int write_size;
int read_only;
.sp

enum
{
    RO_OPTION = 0,
    RW_OPTION,
    READ_SIZE_OPTION,
    WRITE_SIZE_OPTION
};
.sp

const char *mount_opts[] =
{
    [RO_OPTION] = "ro",
    [RW_OPTION] = "rw",
    [READ_SIZE_OPTION] = "rsize",
    [WRITE_SIZE_OPTION] = "wsize",
    NULL
};
.sp

int
main(int argc, char *argv[])
{
    char *subopts, *value;
    int opt;
.sp

    while ((opt = getopt(argc, argv, "at:o:")) != -1)
        switch(opt)
            {
            case 'a':
                do_all = 1;
                break;
            case 't':
                type = optarg;
                break;
            case 'o':
                subopts = optarg;
                while (*subopts != '\\0')
                    switch(getsubopt(&subopts, mount_opts, &value))
                {
                case RO_OPTION:
                    read_only = 1;
                    break;
                case RW_OPTION:
                    read_only = 0;
                    break;
                case READ_SIZE_OPTION:
                    if (value == NULL)
                        abort();
                    read_size = atoi(value);
                    break;
                case WRITE_SIZE_OPTION:
                    if (value == NULL)
                        abort();
                    write_size = atoi(value);
                    break;
                default:
                    /* Unknown suboption. */
                    printf("Unknown suboption `%s'\\n", value);
                    break;
                }
            break;
        default:
            abort();
        }
.sp

    /* Do the real work. */
.sp

    return 0;
}
\fP
.fi
.RE
.SS Parsing Suboptions
.LP
The following example uses the \fIgetsubopt\fP() function to parse
a \fIvalue\fP argument in the \fIoptarg\fP external
variable returned by a call to \fIgetopt\fP().
.sp
.RS
.nf

\fB#include <stdlib.h>
\&...
char *tokens[] = {"HOME", "PATH", "LOGNAME", (char *) NULL };
char *value;
int opt, index;
.sp

while ((opt = getopt(argc, argv, "e:")) != -1) {
    switch(opt)  {
    case 'e' :
        while ((index = getsubopt(&optarg, tokens, &value)) != -1) {
            switch(index) {
\&...
        }
        break;
\&...
    }
}
\&...
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIgetopt\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
\fI<stdlib.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .