getsubopt(3C) getsubopt(3C)
getsubopt - parse suboptions from a string
#include <stdlib.h>
int getsubopt (char **optionp, char *const *tokens, char **valuep);
getsubopt parses 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 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 information
to determine if the presence or lack of a value for this suboption 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.
The following code fragment shows how to process options to the mount
command using getsubopt.
#include <stdlib.h>
char *myopts[] = {
#define READONLY 0
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getsubopt(3C) getsubopt(3C)
"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) {
error_no_arg();
errflag++;
} else
write_size = atoi(value);
break;
case READSIZE : /* process rsize option */
if (value == NULL) {
error_no_arg();
errflag++;
} else
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getsubopt(3C) getsubopt(3C)
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 */
}
.
.
.
}
getopt(3C)
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.
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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