strsep - extract token from string

NAME LIBRARY SYNOPSIS DESCRIPTION RETURN VALUE ATTRIBUTES STANDARDS HISTORY BUGS EXAMPLES Program source SEE ALSO

SYNOPSIS

#include <string.h>

char *strsep(char **restrict stringp, const char *restrict delim);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

strsep():
Since glibc 2.19:
_DEFAULT_SOURCE
glibc 2.19 and earlier:
_BSD_SOURCE

If *stringp is NULL, the strsep() function returns NULL and does nothing else. Otherwise, this function finds the first token in the string *stringp that is delimited by one of the bytes in the string delim. This token is terminated by overwriting the delimiter with a null byte ('\0'), and *stringp is updated to point past the token. In case no delimiter was found, the token is taken to be the entire string *stringp, and *stringp is made NULL.

RETURN VALUE

The strsep() function returns a pointer to the token, that is, it returns the original value of *stringp.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

STANDARDS

None.

HISTORY

4.4BSD.

The strsep() function was introduced as a replacement for strtok(3), since the latter cannot handle empty fields. However, strtok(3) conforms to C89/C99 and hence is more portable.

BUGS

Be cautious when using this function. If you do use it, note that:

	•		This function modifies its first argument.
	•		This function cannot be used on constant strings.
	•		The identity of the delimiting character is lost.

EXAMPLES

The program below is a port of the one found in strtok(3), which, however, doesn’t discard multiple delimiters or empty tokens:

$ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'
1: a/bbb///cc
−−> a
−−> bbb
−−>
−−>
−−> cc
2: xxx
−−> xxx
3: yyy
−−> yyy
4:
−−>

Program source

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{
char *token, *subtoken;
if (argc != 4) {
fprintf(stderr, "Usage: %s string delim subdelim\n", argv[0]);
exit(EXIT_FAILURE);
}
for (unsigned int j = 1; (token = strsep(&argv[1], argv[2])); j++) {
printf("%u: %s\n", j, token);
while ((subtoken = strsep(&token, argv[3])))
printf("\t −−> %s\n", subtoken);
}
exit(EXIT_SUCCESS);
}