strtok

Syntax

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

Parameters

s1

(IN) Points to the string to break into a sequence of tokens.

s2

(IN) Points to the string containing the delimiter characters.

Return Values

If a delimiter is found, returns a pointer to the first byte of a token. On subsequent iterations, if no delimiter is found, returns a NULL pointer.

If s1 does not contain any of the delimiters specified in s2, returns a pointer to s1, and all of s1 is considered to be a token.

Remarks

The strtok function is used to break 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. For example, suppose that s1 and s2 contain the following characters:

  s1: "abcd:efgh:ijkl"
  s2: ":"
  

The first call to strtok would return a pointer to a, because abcd is the first token. The second call to strtok would return a pointer to e, because efgh is the second token. The second and subsequent calls to strtok must pass a NULL pointer as the first argument, in order to get the next token in the string. The strtok function saves a pointer to the following character, from which the next search for a token starts when the first argument is a NULL pointer.

The strtok function replaces each delimiter that it finds with a NULL character, which terminates the current token. Because strtok can modify the original string, that string should be duplicated if the string is to be reused.

The set of delimiters used in the calls to strtok can be different from one call to the next.

See Also

• strcspn
• strpbrk