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 were initially parsed by
getopt()
(see
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.
Because commas delimit suboptions in the option string,
they are not allowed to be part of the suboption
or the value of a suboption.
Similarly, because the equal sign separates a token from its value,
a token must not contain an equals sign.
An example command that uses this syntax is
mount.
mount
allows parameters to be specified with the
-
switch 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 at the end of the string,
otherwise it isolates the suboption
by replacing the comma separator with a null,
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 of the first character.
Otherwise it sets
*valuep
to NULL.
The token vector is organized as a series of pointers to
NULL-terminated strings.
The end of the token vector is identified by NULL.
When
getsubopt()
returns, if
*valuep
is not NULL then the suboption processed included a value.
The calling program can 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 on to another program.
EXTERNAL INFLUENCES
Locale
The
LC_CTYPE
category determines the interpretation of option letters
as single and/or multi-byte characters.
International Code Set Support
Single- and multi-byte character code sets are supported
with the exception of multi-byte-character file names.
EXAMPLES
The following code fragment shows how options can be processed to the
mount
command by using
getsubopt().
char *myopts[] = {
#define READONLY 0
"ro",
#define READWRITE 1
"rw",
#define WRITESIZE 2
"wsize",
#define READSIZE 3
"rsize",
NULL};
main (int argc, char **argv)
{
int sc, c, errflag;
char *options, *value;
extern char *optarg;
extern int optind;
.
.
.
while ((c = getopt(argc, argv, "abf:o:")) != EOF)
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:
/* process unknown token */
error_bad_token(value);
errflag++;
break;
}
}
break;
}
}
if (errflg) {
fprintf(stderr, "usage: . . . ");
exit (2);
}
for ( ; optind < argc; optind++) {
/* process remaining arguments */
.
.
.
}
STANDARDS CONFORMANCE
getsubopt(): SVID3
Printable version
