ref: fa095decfa65ce7fa2d03ad6fb1d75640c0803b1
dir: /doc/man3/strtok.3/
.TH strtok 3 .SH NAME strtok - split a string into tokens .SH SYNOPSIS #include <string.h> char *strtok(char *restrict s1, const char *restrict s2) .SH DESCRIPTION The .BR strtok () function, called in sequence, breaks the string pointed to by .I s1 into a sequence of tokens, each of which is delimited by a character from the string pointed to by .IR s2 . .PP The first call in the sequence has a non-null first argument; subsequent calls in the sequence have a null first argument. .PP The separator string pointed to by .I s2 may be different from call to call. .PP The first call in the sequence searches the string pointed to by .I s1 for the first character that is not contained in the current separator string pointed to by .IR 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. .PP 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 .IR 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. .PP 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. The function returns a pointer to the first character of a token, or a null pointer if there is no token. .SH RETURN VALUE The .BR strtok () function shall return a pointer to the first character of a token, or a null pointer if there is no token. .SH STANDARDS ISO/IEC 9899:1999 Section 7.21.5.8