函数原型：char *strtok(char *s, const char *delim);
char *strsep(char **s, const char *delim);
功能：strtok和strsep两个函数的功能都是用来分解字符串为一组字符串。s为要分解的字符串，delim为分隔符字符串。
返回值：从s开头开始的一个个子串，当没有分割的子串时返回NULL。
相同点：两者都会改变源字符串，想要避免，可以使用strdupa（由allocate函数实现）或strdup（由malloc函数实现）。
strtok函数第一次调用时会把s字符串中所有在delim中出现的字符替换为NULL。然后通过依次调用strtok(NULL, delim)得到各部分子串。
测试代码：
[cpp] view plain copy #include <stdio.h> #include <string.h> int main(void) { char s[] = "hello, world! welcome to china!"; char delim[] = " ,!"; char *token; for(token = strtok(s, delim); token != NULL; token = strtok(NULL, delim)) { printf(token); printf("+"); } printf("n"); return 0; }
输出结果为：hello+world+welcome+china+
For example:
char str[] = "now # is the time for all # good men to come to the # aid of their country"; char delims[] = "#"; char *result = NULL; result = strtok( str, delims ); while( result != NULL ){ printf( "result is "%s"n", result ); result = strtok( NULL, delims ); }The above code will display the following output:
result is "now " result is " is the time for all " result is " good men to come to the " result is " aid of their country" char str2[] = "2011/11/28"; char *buf; char *token; buf = str2; while((token = strsep(&buf, "/")) != NULL){ printf("%sn", token); }输出：
2011 11 28
对于strsep有如下例子:
[cpp] view plain copy #include <stdio.h> #include <string.h> int main(void) { char source[] = "hello, world! welcome to china!"; char delim[] = " ,!"; char *s = strdup(source); char *token; for(token = strsep(&s, delim); token != NULL; token = strsep(&s, delim)) { printf(token); printf("+"); } printf("n"); return 0; } 输出结果为：hello++world++welcome+to+china++
为什么用strtok时子串中间只有一个“+”，而strsep却有多个"+"呢？文档中有如下的解释：
One difference between strsep and strtok_r is that if the input string contains more
than one character from delimiter in a row strsep returns an empty string for each
pair of characters from delimiter. This means that a program normally should test
for strsep returning an empty string before processing it.
大意是：如果输入的串的有连续的多个字符属于delim，（此例source中的逗号+空格，感叹号+空格等就是这种情况），strtok会返回NULL，而strsep会返回空串""。因而我们如果想用strsep函数分割字符串必须进行返回值是否是空串的判断。这也就解释了strsep的例子中有多个"+"的原因。
我们在自己的程序中最好尽量避免使用strtok，转而使用strsep。
下面的说明摘自于最新的Linux内核2.6.29，说明了strtok()已经不再使用，由速度更快的strsep()代替。
/** linux/lib/string.c** Copyright (C) 1991, 1992 Linus Torvalds*/
/** stupid library routines.. The optimized versions should generally be found
* as inline code in <asm-xx/string.h>
* These are buggy as well..
* * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
* - Added strsep() which will replace strtok() soon (because strsep() is
* reentrant and should be faster). Use only strsep() in new code, please.
** * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>,
* Matthew Hawkins <matt@mh.dropbear.id.au>
* - Kissed strtok() goodbye
*/