GETSUBOPT

NAME

SYNOPSIS

int getsubopt(char **optionp, char * const *tokens, char **valuep);  

DESCRIPTION

ro,name=xyz

The tokens argument is a pointer to a NULL-terminated list of the tokens that getsubopt() will look for in optionp. The tokens should be distinct, null-terminated strings containing at least one character, with no embedded equal signs or commas.

Each call to getsubopt() returns information about the next unprocessed suboption in optionp. The first equal sign in a suboption (if any) is interpreted as a separator between the name and the value of that suboption. The value extends to the next comma, or (for the last suboption) to the end of the string. If the name of the suboption matches a known name from tokens, and a value string was found, getsubopt() sets *valuep to the address of that string. The first comma in optionp is overwritten with a null byte, so *valuep is precisely the "value string" for that suboption.

If the suboption is recognized, but no value string was found, *valuep is set to NULL.

When getsubopt() returns, optionp points to the next suboption, or to the null character at the end of the string if the last suboption was just processed.  

RETURN VALUE

Since *optionp is changed, the first suboption before the call to getsubopt() is not (necessarily) the same as the first suboption after getsubopt().  

CONFORMING TO

NOTES

Since getsubopt() overwrites any commas it finds in the string *optionp, that string must be writable; it cannot be a string constant.  

EXAMPLE

#define _XOPEN_SOURCE 500
#include <stdlib.h>
#include <assert.h>
#include <stdio.h>

int main(int argc, char **argv)
{
    enum {
        RO_OPT = 0,
        RW_OPT,
        NAME_OPT
    };
    char *const token[] = {
        [RO_OPT]   = "ro",
        [RW_OPT]   = "rw",
        [NAME_OPT] = "name",
        NULL
    };
    char *subopts;
    char *value;
    int opt;

    int readonly = 0;
    int readwrite = 0;
    char *name = NULL;
    int errfnd = 0;

    while ((opt = getopt(argc, argv, "o:")) != -1) {
        switch (opt) {
        case aqoaq:
            subopts = optarg;
            while (*subopts != aq\0aq && !errfnd) {

            switch (getsubopt(&subopts, token, &value)) {
            case RO_OPT:
                readonly = 1;
                break;

            case RW_OPT:
                readwrite = 1;
                break;

            case NAME_OPT:
                if (value == NULL) {
                    fprintf(stderr, "Missing value for "
                            "suboption aq%saq\n", token[NAME_OPT]);
                    errfnd = 1;
                    continue;
                }

                name = value;
                break;

            default:
                fprintf(stderr, "No match found "
                        "for token: /%s/\n", value);
                errfnd = 1;
                break;
            }
        }
        if (readwrite && readonly) {
            fprintf(stderr, "Only one of aq%saq and aq%saq can be "
                    "specified\n", token[RO_OPT], token[RW_OPT]);
            errfnd = 1;
        }
        break;

        default:
            errfnd = 1;
        }
    }

    if (errfnd || argc == 1) {
        fprintf(stderr, "\nUsage: %s -o <suboptstring>\n", argv[0]);
        fprintf(stderr, "suboptions are aqroaq, aqrwaq, "
                "and aqname=<value>aq\n");
        exit(EXIT_FAILURE);
    }

    /* Remainder of program... */

    exit(EXIT_SUCCESS);
}

SEE ALSO

COLOPHON