strsep(3)

NAME#

strsep - extract token from string

LIBRARY#

Standard C library (libc, -lc)

SYNOPSIS#

#include <string.h>

char *strsep(char **restrict \nstringp\n, const char *restrict \ndelim\n);

strsep():

\n
    Since glibc 2.19:
\n
        _DEFAULT_SOURCE
\n
    glibc 2.19 and earlier:
\n
        _BSD_SOURCE

DESCRIPTION#

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:

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

Program source#

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

SEE ALSO#

memchr(3), strchr(3), string(3), strpbrk(3), strspn(3), strstr(3), strtok(3)