Name
strsep - extract token from stringLibrary
Standard C library ( libc ", " -lc )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
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 stringdelim
. This token is terminated by overwriting the delimiter with a null byte ('\e0'), 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).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
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\en", argv[0]); exit(EXIT_FAILURE); } for (unsigned int j = 1; (token = strsep(&argv[1], argv[2])); j++) { printf("%u: %s\en", j, token); while ((subtoken = strsep(&token, argv[3]))) printf("\et --> %s\en", subtoken); } exit(EXIT_SUCCESS); }