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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 .