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 is a function to parse suboptions in a flag argument that
was initially parsed by getopt(3C). 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 suboption. A command that uses this syntax is
mount(1M), which allows you 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 subobtion, 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
information to determine if the presence or lack of a value for this
subobtion 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 on to
another program.
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getsubopt(3C) getsubopt(3C)
DIAGNOSTICS
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.
EXAMPLE
The following code fragment shows how you might process options to
the mount(1M) command using getsubopt(3C).
#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;
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getsubopt(3C) getsubopt(3C)
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;
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 */
}
.
.
.
}
NOTES
During parsing, commas in the option input string are changed to null
characters.
White space in tokens or token-value pairs must be protected from the
shell by quotes.
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getsubopt(3C) getsubopt(3C)
SEE ALSO
getopt(3C).
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