strtok.3 (1900B)
1 .TH strtok 3 2 .SH NAME 3 strtok - split a string into tokens 4 .SH SYNOPSIS 5 #include <string.h> 6 7 char *strtok(char *restrict s1, const char *restrict s2) 8 .SH DESCRIPTION 9 The 10 .BR strtok () 11 function, called in sequence, 12 breaks the string pointed to by 13 .I s1 14 into a sequence of tokens, 15 each of which is delimited by a character 16 from the string pointed to by 17 .IR s2 . 18 .PP 19 The first call in the sequence has a non-null first argument; 20 subsequent calls in the sequence have a null first argument. 21 .PP 22 The separator string pointed to by 23 .I s2 24 may be different from call to call. 25 .PP 26 The first call in the sequence 27 searches the string pointed to by 28 .I s1 29 for the first character 30 that is not contained in the current separator 31 string pointed to by 32 .IR s2 . 33 If no such character is found, 34 then there are 35 no tokens in the string pointed to by s1 36 and the strtok function returns a null pointer. 37 If such a character is found, 38 it is the start of the first token. 39 .PP 40 The strtok function then searches from there 41 for a character that is contained 42 in the current separator string. 43 If no such character is found, 44 the current token extends to 45 the end of the string pointed to by 46 .IR s1 , 47 and subsequent searches for a token will return a null pointer. 48 If such a character is found, 49 it is overwritten by a null character, 50 which terminates the current token. 51 The strtok function saves 52 a pointer to the following character, 53 from which the next search for a token will start. 54 .PP 55 Each subsequent call, 56 with a null pointer as the value of the first argument, 57 starts searching from the saved pointer 58 and behaves as described above. 59 The function returns a pointer to the first 60 character of a token, 61 or a null pointer if there is no token. 62 .SH RETURN VALUE 63 The 64 .BR strtok () 65 function shall return a pointer to the first character of a token, 66 or a null pointer if there is no token. 67 .SH STANDARDS 68 ISO/IEC 9899:1999 Section 7.21.5.8