getsubopt(3C) getsubopt(3C)
NAME
getsubopt - parse suboptions from a string
SYNOPSIS
#include <stdlib.h>
int getsubopt (char **optionp, char * const *tokens, char **valuep);
DESCRIPTION
getsubopt() parses suboptions in a flag argument that was initially
parsed by getopt(). These suboptions are separated by commas and may
consist of either a single token or a token-value pair separated by an
equal sign. Since commas delimit suboptions in the option string, they
are not allowed to be part of the suboption or the value of a subop-
tion. A command that uses this syntax is mount(1M), which allows the
user to specify mount parameters with the -o option as follows:
mount -o rw,hard,bg,wsize=1024 speed:/usr /usr
In this example there are four suboptions: rw, hard, bg, and wsize,
the last of which has an associated value of 1024.
getsubopt() takes the address of a pointer to the option string, a
vector of possible tokens, and the address of a value string pointer.
It returns the index of the token that matched the suboption in the
input string or -1 if there was no match. If the option string at
optionp contains only one suboption, getsubopt() updates optionp to
point to the null character at the end of the string; otherwise it
isolates the suboption by replacing the comma separator with a null
character, and updates optionp to point to the start of the next
suboption. If the suboption has an associated value, getsubopt()
updates valuep to point to the value's first character. Otherwise it
sets valuep to NULL.
The token vector is organized as a series of pointers to null strings.
The end of the token vector is identified by a null pointer.
When getsubopt() returns, if valuep is not NULL, then the suboption
processed included a value. The calling program may use this informa-
tion to determine if the presence or lack of a value for this subop-
tion is an error.
Additionally, when getsubopt() fails to match the suboption with the
tokens in the tokens array, the calling program should decide if this
is an error, or if the unrecognized option should be passed to another
program.
Page 1 Reliant UNIX 5.44 Printed 11/98
getsubopt(3C) getsubopt(3C)
EXAMPLE
The following code fragment shows how to process options to the mount
command using getsubopt().
#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 != '\0')
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) {
errornoarg();
errflag++;
} else
writesize = atoi(value);
break;
Page 2 Reliant UNIX 5.44 Printed 11/98
getsubopt(3C) getsubopt(3C)
case READSIZE : /* process rsize option */
if (value == NULL) {
errornoarg();
errflag++;
} else
readsize = atoi(value);
break;
default : /* process unknown token */
errorbadtoken(value);
errflag++;
break;
}
}
break;
}
}
if (errflag) {
/* print usage instructions etc. */
}
for (; optind<argc; optind++) {
/* process remaining arguments */
}
...}
RESULT
getsubopt() returns -1 when the token it is scanning is not in the
token vector. The variable addressed by valuep contains a pointer to
the first character of the token that was not recognized rather than a
pointer to a value for that token.
The variable addressed by optionp points to the next option to be
parsed, or a null character if there are no more options.
NOTES
During parsing, commas in the option input string are changed to null
characters. White space in tokens or token-value pairs must be pro-
tected from the shell by quotes.
SEE ALSO
getopt(3C).
Page 3 Reliant UNIX 5.44 Printed 11/98