ISO/IEC 9899:1999 (E) ŠISO/IEC
7.21.5.8 The strtok function
Synopsis
1 #include <string.h>
char *strtok(char * restrict s1,const char * restrict s2);
Description
2 A sequence of calls to the strtok function breaks the string pointed
to by s1 into a sequence of tokens, each of which is delimited by a
character from the string pointed to by s2. The first call in the
sequence has a non-null first argument; subsequent calls in the
sequence have a null first argument. The separator string pointed to
by s2 may be different from call to call.
3 The first call in the sequence searches the string pointed to by s1
for the first character that is not contained in the current
separator string pointed to by s2. If no such character
is found, then there are no tokens in the string pointed to by s1 and
the strtok function returns a null pointer. If such a character is
found, it is the start of the first token.
4 The strtok function then searches from there for a character that is
contained in the current separator string. If no such character is
found, the current token extends to the end of the string pointed to
by s1, and subsequent searches for a token will return a null
pointer. If such a character is found, it is overwritten by a null
character, which terminates the current token. The strtok function
saves a pointer to the following character, from which the next
search for a token will start.
5 Each subsequent call, with a null pointer as the value of the first
argument, starts searching from the saved pointer and behaves as
described above.
6 The implementation shall behave as if no library function calls the
strtok function.
Returns
7 The strtok function returns a pointer to the first character of a
token, or a null pointer if there is no token.
8 EXAMPLE
Code:
#include <string.h>
static char str[] = "?a???b,,,#c";
char *t;
t = strtok(str, "?"); // t points to the token "a"
t = strtok(NULL, ","); // t points to the token "??b"
t = strtok(NULL, "#,"); // t points to the token "c"
t = strtok(NULL, "?"); // t is a null pointer