strtok:#include <string.h>char *strtok(char *str, const char *delim);char *strtok_r(char *str, const char *delim, char **saveptr);功能：分解字符串为一组标记串。str为要分解的字符串，，delim为分隔符字符串。说明：首次调用时，str必须指向要分解的字符串，随后调用要把s设成NULL。 strtok在str中查找包含在delim中的字符并用NULL(‘/0’)来替换，直到找遍整个字符串。 返回指向下一个标记串。当没有标记串时则返回空字符NULL。实例：用strtok来判断ip地址是否合法：ip_strtok.c：
编译运行：
[root@localhost liuxltest]# uname -r2.6.26 [root@localhost liuxltest]# gcc -Wall ip_strtok.c -o ip_strtok[root@localhost liuxltest]# ./ip_strtok 172.18.4.255172 p = 1818 p = 44 p = 255255 p = (null)ok! ip correct! ip=172.18.4.255[root@localhost liuxltest]# ./ip_strtok 172.18.ip param format error
strtok实现函数：
xl_strtok.c
strtok源码：
/*********************************************************************//****strtok.c – tokenize a string with given delimiters** Copyright (c) Microsoft Corporation. All rights reserved.**Purpose:* defines strtok() – breaks string into series of token* via repeated calls.********************************************************************************/#include <cruntime.h>#include <string.h>#ifdef _SECURE_VERSION#include <internal.h>#else/* _SECURE_VERSION */#include <mtdll.h>#endif/* _SECURE_VERSION *//****char *strtok(string, control) – tokenize string with delimiter in control**Purpose:* strtok considers the string to consist of a sequence of zero or more* text tokens separated by spans of one or more control chars. the first* call, with string specified, returns a pointer to the first char of the* first token, and will write a null char into string immediately* following the returned token. subsequent calls with zero for the first* argument (string) will work thru the string until no tokens remain. the* control string may be different from call to call. when no tokens remain* in string a NULL pointer is returned. remember the control chars with a* bit map, one bit per ascii char. the null char is always a control char.**Entry:* char *string – string to tokenize, or NULL to get next token* char *control – string of characters to use as delimiters**Exit:* returns pointer to first token in string, or if string* was NULL, to next token* returns NULL when no more tokens remain.**Uses:**Exceptions:********************************************************************************/#ifdef _SECURE_VERSION#define _TOKEN *context#else/* _SECURE_VERSION */#define _TOKEN ptd->_token#endif/* _SECURE_VERSION */#ifdef _SECURE_VERSIONchar * __cdecl strtok_s ( char * string, const char * control, char ** context )#else/* _SECURE_VERSION */char * __cdecl strtok ( char * string, const char * control )#endif/* _SECURE_VERSION */{ unsigned char *str; const unsigned char *ctrl = control; unsigned char map[32]; int count;#ifdef _SECURE_VERSION /* validation section */ _VALIDATE_RETURN(context != NULL, EINVAL, NULL); _VALIDATE_RETURN(string != NULL || *context != NULL, EINVAL, NULL); _VALIDATE_RETURN(control != NULL, EINVAL, NULL); /* no static storage is needed for the secure version */#else/* _SECURE_VERSION */ _ptiddata ptd = _getptd();#endif/* _SECURE_VERSION */ /* Clear control map */ for (count = 0; count < 32; count++) map[count] = 0; /* Set bits in delimiter table */ do { map[*ctrl >> 3] |= (1 << (*ctrl & 7)); } while (*ctrl++); /* Initialize str */ /* If string is NULL, set str to the saved * pointer (i.e., continue breaking tokens out of the string * from the last strtok call) */ if (string) str = string; else str = _TOKEN; /* Find beginning of token (skip over leading delimiters). Note that * there is no token iff this loop sets str to point to the terminal * null (*str == ‘/0’) */ while ( (map[*str >> 3] & (1 << (*str & 7))) && *str ) str++; string = str; /* Find the end of the token. If it is not the end of the string, * put a null there. */ for ( ; *str ; str++ ) if ( map[*str >> 3] & (1 << (*str & 7)) ) { *str++ = ‘/0’; break; } /* Update nextoken (or the corresponding field in the per-thread data * structure */ _TOKEN = str; /* Determine if a token has been found. */ if ( string == str ) return NULL; else return string;}
莫找借口失败，只找理由成功。(不为失败找理由，要为成功找方法
