| STRTOK(3) | Library Functions Manual | STRTOK(3) |
strtok, strtok_r —
#include <string.h>
char *
strtok(char
* restrict str, const
char * restrict sep);
char *
strtok_r(char
*str, const char
*sep, char
**lasts);
strtok() function is used to isolate sequential
tokens in a nul-terminated 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 further 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 subsequent 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 necessary to limit
tokenizing to a single string at a time when using
strtok_r().
#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”.
strtok() function conforms to ANSI
X3.159-1989 (“ANSI C89”). The
strtok_r() function conforms to IEEE
Std 1003.1c-1995 (“POSIX.1c”).
strtok(), if handed a string containing
only delimiter characters, 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 starting point, such a sequence of calls
would always return NULL.
| August 11, 2002 | NetBSD 9.2 |