getsubopt(3) - Linux manual page (original) (raw)
getsubopt(3) Library Functions Manual getsubopt(3)
NAME top
getsubopt - parse suboption arguments from a stringLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <stdlib.h>**
**int getsubopt(char restrict** _optionp_**, char *const *restrict** _tokens_**,**
**char restrict** _valuep_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**getsubopt**():
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809LDESCRIPTION top
**getsubopt**() parses the list of comma-separated suboptions provided
in _optionp_. (Such a suboption list is typically produced when
[getopt(3)](../man3/getopt.3.html) is used to parse a command line; see for example the _-o_
option of [mount(8)](../man8/mount.8.html).) Each suboption may include an associated
value, which is separated from the suboption name by an equal
sign. The following is an example of the kind of string that
might be passed in _optionp_:
**ro,name=xyz**
The _tokens_ argument is a pointer to a NULL-terminated array of
pointers to the tokens that **getsubopt**() will look for in _optionp_.
The tokens should be distinct, null-terminated strings containing
at least one character, with no embedded equal signs or commas.
Each call to **getsubopt**() returns information about the next
unprocessed suboption in _optionp_. The first equal sign in a
suboption (if any) is interpreted as a separator between the name
and the value of that suboption. The value extends to the next
comma, or (for the last suboption) to the end of the string. If
the name of the suboption matches a known name from _tokens_, and a
value string was found, **getsubopt**() sets _*valuep_ to the address of
that string. The first comma in _optionp_ is overwritten with a
null byte, so _*valuep_ is precisely the "value string" for that
suboption.
If the suboption is recognized, but no value string was found,
_*valuep_ is set to NULL.
When **getsubopt**() returns, _optionp_ points to the next suboption, or
to the null byte ('\0') at the end of the string if the last
suboption was just processed.RETURN VALUE top
If the first suboption in _optionp_ is recognized, **getsubopt**()
returns the index of the matching suboption element in _tokens_.
Otherwise, -1 is returned and _*valuep_ is the entire _name_**[=**_value_**]**
string.
Since _*optionp_ is changed, the first suboption before the call to
**getsubopt**() is not (necessarily) the same as the first suboption
after **getsubopt**().ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **getsubopt**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001.NOTES top
Since **getsubopt**() overwrites any commas it finds in the string
_*optionp_, that string must be writable; it cannot be a string
constant.EXAMPLES top
The following program expects suboptions following a "-o" option.
#define _XOPEN_SOURCE 500
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
int
main(int argc, char *argv[])
{
enum {
RO_OPT = 0,
RW_OPT,
NAME_OPT
};
char *const token[] = {
[RO_OPT] = "ro",
[RW_OPT] = "rw",
[NAME_OPT] = "name",
NULL
};
char *subopts;
char *value;
int opt;
int readonly = 0;
int readwrite = 0;
char *name = NULL;
int errfnd = 0;
while ((opt = getopt(argc, argv, "o:")) != -1) {
switch (opt) {
case 'o':
subopts = optarg;
while (*subopts != '\0' && !errfnd) {
switch (getsubopt(&subopts, token, &value)) {
case RO_OPT:
readonly = 1;
break;
case RW_OPT:
readwrite = 1;
break;
case NAME_OPT:
if (value == NULL) {
fprintf(stderr,
"Missing value for suboption '%s'\n",
token[NAME_OPT]);
errfnd = 1;
continue;
}
name = value;
break;
default:
fprintf(stderr,
"No match found for token: /%s/\n", value);
errfnd = 1;
break;
}
}
if (readwrite && readonly) {
fprintf(stderr,
"Only one of '%s' and '%s' can be specified\n",
token[RO_OPT], token[RW_OPT]);
errfnd = 1;
}
break;
default:
errfnd = 1;
}
}
if (errfnd || argc == 1) {
fprintf(stderr, "\nUsage: %s -o <suboptstring>\n", argv[0]);
fprintf(stderr,
"suboptions are 'ro', 'rw', and 'name=<value>'\n");
exit(EXIT_FAILURE);
}
/* Remainder of program... */
exit(EXIT_SUCCESS);
}SEE ALSO top
[getopt(3)](../man3/getopt.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 getsubopt(3)
Pages that refer to this page:getopt(3)