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strsep(3) Library Functions Manual strsep(3) strsep - extract token from string
Standard C library (libc, -lc)
#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. The strsep() function returns a pointer to the token, that is, it returns the original value of *stringp.
For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │ Interface │ Attribute │ Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │ strsep() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘
BSD.
4.4BSD. The strsep() function was introduced as a replacement for strtok(3), since the latter cannot handle empty fields.
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.
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); } memchr(3), strchr(3), string(3), strpbrk(3), strspn(3), strstr(3), strtok(3)
This page is part of the man-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Linux man-pages 6.15 2025-05-17 strsep(3) Pages that refer to this page: memchr(3), strchr(3), string(3), strpbrk(3), strspn(3), strstr(3), strtok(3)
| HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. | |