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strtok

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< c‎ | string‎ | byte
Revision as of 16:30, 1 July 2013 by P12bot (Talk | contribs)

Defined in header <string.h>
char *strtok( char          *str, const char          *delim );
(until C99)
char *strtok( char *restrict str, const char *restrict delim );
(since C99)

Finds the next token in a null-terminated byte string pointed to by str. The separator characters are identified by null-terminated byte string pointed to by delim.

This function is designed to be called multiples times to obtain successive tokens from the same string.

  • If str != NULL, the call is treated as the first call to strtok for this particular string. The function searches for the first character which is not contained in delim.
  • If no such character was found, there are no tokens in str at all, and the function returns a null pointer.
  • If such character was found, is it the beginning of the token. The function then searches from that point on for the first character that is contained in delim.
  • If no such character was found, str has only one token, and the future calls to strtok will return a null pointer
  • If such character was found, it is replaced by the null character '\0' and the pointer to the following character is stored in a static location for subsequent invocations.
  • The function then returns the pointer to the beginning of the token
  • If str == NULL, the call is treated as a subsequent calls to strtok: the function continues from where it left in previous invocation. The behavior is the same as if the previously stored pointer is passed as str.

Contents

Parameters

str - pointer to the null-terminated byte string to tokenize
delim - pointer to the null-terminated byte string identifying delimiters

Return value

Pointer to the beginning of the next token or NULL if there are no more tokens.

Note

This function is destructive: it writes the '\0' characters in the elements of the string str. In particular, a string literal cannot be used as the first argument of strtok.

Each call to this function modifies a static variable: is not thread safe.

Example

See also