STRTOK(3) BSD Library Functions Manual STRTOK(3)NAME
strtok, strtok_r — string tokens
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <string.h>
char *
strtok(char * restrict str, const char * restrict sep);
char *
strtok_r(char *str, const char *sep, char **lasts);
DESCRIPTION
The strtok() function is used to isolate sequential tokens in a nul-ter‐
minated string, str. These tokens are separated in the string by at
least one of the characters in sep. The first time that strtok() is
called, str should be specified; subsequent calls, wishing to obtain fur‐
ther tokens from the same string, should pass a null pointer instead.
The separator string, sep, must be supplied each time, and may change
between calls.
The strtok() function returns a pointer to the beginning of each subse‐
quent token in the string, after replacing the separator character itself
with a NUL character. Separator characters at the beginning of the
string or at the continuation point are skipped so that zero length
tokens are not returned. When no more tokens remain, a null pointer is
returned.
The strtok_r() function implements the functionality of strtok() but is
passed an additional argument, lasts, which points to a user-provided
pointer which is used by strtok_r() to store state which needs to be kept
between calls to scan the same string; unlike strtok(), it is not neces‐
sary to limit tokenizing to a single string at a time when using
strtok_r().
EXAMPLES
The following will construct an array of pointers to each individual word
in the string s:
#define MAXTOKENS 128
char s[512], *p, *tokens[MAXTOKENS];
char *last;
int i = 0;
snprintf(s, sizeof(s), "cat dog horse cow");
for ((p = strtok_r(s, " ", &last)); p;
(p = strtok_r(NULL, " ", &last)), i++) {
if (i < MAXTOKENS - 1)
tokens[i] = p;
}
tokens[i] = NULL;
That is, tokens[0] will point to "cat", tokens[1] will point to "dog",
tokens[2] will point to "horse", and tokens[3] will point to "cow".
SEE ALSOindex(3), memchr(3), rindex(3), strchr(3), strcspn(3), strpbrk(3),
strrchr(3), strsep(3), strspn(3), strstr(3)STANDARDS
The strtok() function conforms to ANSI X3.159-1989 (“ANSI C89”). The
strtok_r() function conforms to IEEE Std 1003.1c-1995 (“POSIX.1”).
BUGS
The System V strtok(), if handed a string containing only delimiter char‐
acters, will not alter the next starting point, so that a call to
strtok() with a different (or empty) delimiter string may return a
non-NULL value. Since this implementation always alters the next start‐
ing point, such a sequence of calls would always return NULL.
BSD August 11, 2002 BSD
