原型：extern char *strtok(char *s, char *delim);
用法：#include <string.h>
功能：分解字符串为一组标记串。s为要分解的字符串，delim为分隔符字符串。
说明：首次调用时，s必须指向要分解的字符串，随后调用要把s设成NULL。
strtok在s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。
举例：
// strtok.c
#include <syslib.h>
#include <string.h>
#include <stdio.h>
main()
{
char *s="Golden Global View";
char *d=" ";
char *p;
clrscr();
p=strtok(s,d);
while(p)
{
printf("%s/n",s);
strtok(NULL,d);
}
getchar();
return 0;
}
源码：
/***
*strtok.c - tokenize a string with given delimiters
*
* Copyright (c) 1989-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines strtok() - breaks string into series of token
* via repeated calls.
*
*******************************************************************************/
#include <cruntime.h>
#include <string.h>
#ifdef _MT
#include <mtdll.h>
#endif /* _MT */
/***
*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:
*
*******************************************************************************/
char * __cdecl strtok (
char * string,
const char * control
)
{
unsigned char *str;
const unsigned char *ctrl = control;
unsigned char map[32];
int count;
#ifdef _MT
_ptiddata ptd = _getptd();
#else /* _MT */
static char *nextoken;
#endif /* _MT */
/* 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
#ifdef _MT
str = ptd->_token;
#else /* _MT */
str = nextoken;
#endif /* _MT */
/* 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 */
#ifdef _MT
ptd->_token = str;
#else /* _MT */
nextoken = str;
#endif /* _MT */
/* Determine if a token has been found. */
if ( string == str )
return NULL;
else
return string;
}
map[*ctrl >> 3] |= (1 << (*ctrl & 7))说明：
map[*ctrl >> 3] |= (1 << (*ctrl & 7));
这句是这样的意思
首先map[32]是个uchar型数组，数组每一个是8位，其中每一位可以表示一个字符，32×8=256,这样的话，map[32]中有256个bit，每个bit表示一个ASCII码，那么可以表示256个ASCII码。
*ctrl >> 3，表示将安ascii码，给其分类，*ctrl >> 3表示，除以8的意思，将ascii每八位分为一组，也就是map[32]中的一个。
1 << (*ctrl & 7)，这个是这样的意思，7表示为二进制就是00000111，这样的话，相当于是一个数除以8后剩余的余数。1 << (*ctrl & 7)，就是将二进制00000001，向右移动(*ctrl & 7)个位。
map[*ctrl >> 3] |= (1 << (*ctrl & 7))，就是表示将map[*ctrl >> 3]中的(*ctrl & 7)＋1位设为1，表示在该位置查询到一个ascii字符。
这样做以后，就相当于简历了一个表，只要查询相应的位是否为1，就知道该字符，在strtok的字符串中是否出现过。