C in a Nutshell

Name

strtok

Synopsis

Divides a string into tokens

#include <string.h>
char *strtok( char * restrict s1, const char * restrict s2 );

The strtok() function isolates tokens in the string addressed by s1 that are delimited by any of the characters contained in the string addressed by s2. The tokens are identified one at a time by successive calls to strtok(). On calls after the first, the s1 argument is a null pointer.

On the first call, strtok() searches in s1 for the first character that does not match any character in s2, behavior that is similar to the strspn() function. The first such character found is considered to be the beginning of a token. Then strtok() searches further for the first character that does match any of the characters in s2—or the null character that terminates the string, whichever comes first—similarly to the strcspn() function. This is considered to be the delimiter that ends the token. strtok() then replaces this ending delimiter with '\0', and returns a pointer to the beginning of the token (or a null pointer if no token was found), while saving an internal, static pointer to the next character after the ending delimiter for use in subsequent strtok() calls.

On each subsequent call with a null pointer as the s1 argument, strtok() behaves similarly, but starts the search at the character that follows the previous delimiter. You can specify a different set of delimiters in the s2 argument on each call. The locations that strtok() reads from using s2 and writes to ...