NAME
getsubopt - parse suboption arguments from a string
SYNOPSIS
#include <stdlib.h>
int getsubopt(char **optionp, char * const *keylistp, char **valuep);
DESCRIPTION
The getsubopt() function shall parse suboption arguments in a flag
argument. Such options often result from the use of getopt().
The getsubopt() argument optionp is a pointer to a pointer to the
option argument string. The suboption arguments shall be separated by
commas and each may consist of either a single token, or a token-value
pair separated by an equal sign.
The keylistp argument shall be a pointer to a vector of strings. The
end of the vector is identified by a null pointer. Each entry in the
vector is one of the possible tokens that might be found in *optionp.
Since commas delimit suboption arguments in optionp, they should not
appear in any of the strings pointed to by keylistp. Similarly, because
an equal sign separates a token from its value, the application should
not include an equal sign in any of the strings pointed to by keylistp.
The valuep argument is the address of a value string pointer.
If a comma appears in optionp, it shall be interpreted as a suboption
separator. After commas have been processed, if there are one or more
equal signs in a suboption string, the first equal sign in any
suboption string shall be interpreted as a separator between a token
and a value. Subsequent equal signs in a suboption string shall be
interpreted as part of the value.
If the string at *optionp contains only one suboption argument
(equivalently, no commas), getsubopt() shall update *optionp to point
to the null character at the end of the string. Otherwise, it shall
isolate the suboption argument by replacing the comma separator with a
null character, and shall update *optionp to point to the start of the
next suboption argument. If the suboption argument has an associated
value (equivalently, contains an equal sign), getsubopt() shall update
*valuep to point to the value’s first character. Otherwise, it shall
set *valuep to a null pointer. The calling application may use this
information to determine whether the presence or absence of a value for
the suboption is an error.
Additionally, when getsubopt() fails to match the suboption argument
with a token in the keylistp array, the calling application should
decide if this is an error, or if the unrecognized option should be
processed in another way.
RETURN VALUE
The getsubopt() function shall return the index of the matched token
string, or -1 if no token strings were matched.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
#include <stdio.h>
#include <stdlib.h>
int do_all;
const char *type;
int read_size;
int write_size;
int read_only;
enum
{
RO_OPTION = 0,
RW_OPTION,
READ_SIZE_OPTION,
WRITE_SIZE_OPTION
};
const char *mount_opts[] =
{
[RO_OPTION] = "ro",
[RW_OPTION] = "rw",
[READ_SIZE_OPTION] = "rsize",
[WRITE_SIZE_OPTION] = "wsize",
NULL
};
int
main(int argc, char *argv[])
{
char *subopts, *value;
int opt;
while ((opt = getopt(argc, argv, "at:o:")) != -1)
switch(opt)
{
case ’a’:
do_all = 1;
break;
case ’t’:
type = optarg;
break;
case ’o’:
subopts = optarg;
while (*subopts != ’\0’)
switch(getsubopt(&subopts, mount_opts, &value))
{
case RO_OPTION:
read_only = 1;
break;
case RW_OPTION:
read_only = 0;
break;
case READ_SIZE_OPTION:
if (value == NULL)
abort();
read_size = atoi(value);
break;
case WRITE_SIZE_OPTION:
if (value == NULL)
abort();
write_size = atoi(value);
break;
default:
/* Unknown suboption. */
printf("Unknown suboption ‘%s’\n", value);
break;
}
break;
default:
abort();
}
/* Do the real work. */
return 0;
}
Parsing Suboptions
The following example uses the getsubopt() function to parse a value
argument in the optarg external variable returned by a call to
getopt().
#include <stdlib.h>
...
char *tokens[] = {"HOME", "PATH", "LOGNAME", (char *) NULL };
char *value;
int opt, index;
while ((opt = getopt(argc, argv, "e:")) != -1) {
switch(opt) {
case ’e’ :
while ((index = getsubopt(&optarg, tokens, &value)) != -1) {
switch(index) {
...
}
break;
...
}
}
...
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
getopt() , the Base Definitions volume of IEEE Std 1003.1-2001,
<stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .