getsubopt(3C) COMPATIBILITY FUNCTIONS 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 ini-
tially 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 suboption. A com-
mand that uses this syntax is mount(1M), which allows the
user to specify mount parameters with the -o option as fol-
lows:
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 con-
tains 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 to another program.
EXAMPLE
The following code fragment shows how to process options to
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getsubopt(3C) COMPATIBILITY FUNCTIONS getsubopt(3C)
the mount command using getsubopt.
#include <stdlib.h>
char *myopts[] = {
#define READONLY 0
"ro",
#define READWRITE 1
"rw",
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getsubopt(3C) COMPATIBILITY FUNCTIONS getsubopt(3C)
#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
read_size = atoi(value);
break;
default :
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getsubopt(3C) COMPATIBILITY FUNCTIONS getsubopt(3C)
/* process unknown token */
error_bad_token(value);
errflag++;
break;
}
}
break;
}
}
if (errflag) {
/* print usage instructions etc. */
}
for (; optind<argc; optind++) {
/* process remaining arguments */
}
.
.
.
}
SEE ALSO
getopt(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.
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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