一些非常好用而被人们忽略或遗忘的函数总汇

函数名: strstr
功 能: 在串中查找指定字符串的第一次出现
用 法: char *strstr(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
   char *str1 = "Borland International", *str2 = "nation", *ptr;

   ptr = strstr(str1, str2);
   printf("The substring is: %s\n", ptr);
   return 0;
}

函数名: stpcpy
功 能: 拷贝一个字符串到另一个
用 法: char *stpcpy(char *destin, char *source);
程序例:

#include
#include

int main(void)
{
   char string[10];
   char *str1 = "abcdefghi";

   stpcpy(string, str1);
   printf("%s\n", string);
   return 0;
}

函数名: strcat
功 能: 字符串拼接函数
用 法: char *strcat(char *destin, char *source);
程序例:

#include
#include

int main(void)
{
   char destination[25];
   char *blank = " ", *c = "C++", *Borland = "Borland";

   strcpy(destination, Borland);
   strcat(destination, blank);
   strcat(destination, c);

   printf("%s\n", destination);
   return 0;
}

函数名: strchr
功 能: 在一个串中查找给定字符的第一个匹配之处\
用 法: char *strchr(char *str, char c);
程序例:

#include
#include

int main(void)
{
    char string[15];
    char *ptr, c = 'r';

    strcpy(string, "This is a string");
    ptr = strchr(string, c);
    if (ptr)
       printf("The character %c is at position: %d\n", c, ptr-string);
    else
       printf("The character was not found\n");
    return 0;
}

函数名: strcmp
功 能: 串比较
用 法: int strcmp(char *str1, char *str2);
看Asic码，str1>str2，返回值 > 0；两串相等，返回0
程序例:

#include
#include

int main(void)
{
    char *buf1 = "aaa", *buf2 = "bbb", *buf3 = "ccc";
    int ptr;

    ptr = strcmp(buf2, buf1);
    if (ptr > 0)
       printf("buffer 2 is greater than buffer 1\n");
    else
       printf("buffer 2 is less than buffer 1\n");

    ptr = strcmp(buf2, buf3);
    if (ptr > 0)
       printf("buffer 2 is greater than buffer 3\n");
    else
       printf("buffer 2 is less than buffer 3\n");

    return 0;
}

函数名: strncmpi
功 能: 将一个串中的一部分与另一个串比较, 不管大小写
用 法: int strncmpi(char *str1, char *str2, unsigned maxlen);
程序例:

#include
#include

int main(void)
{
   char *buf1 = "BBB", *buf2 = "bbb";
   int ptr;

   ptr = strcmpi(buf2, buf1);

   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1\n");

   if (ptr < 0)
      printf("buffer 2 is less than buffer 1\n");

   if (ptr == 0)
      printf("buffer 2 equals buffer 1\n");

   return 0;
}

函数名: strcpy
功 能: 串拷贝
用 法: char *strcpy(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
    char string[10];
    char *str1 = "abcdefghi";

    strcpy(string, str1);
    printf("%s\n", string);
    return 0;
}

函数名: strcspn
功 能: 在串中查找第一个给定字符集内容的段
用 法: int strcspn(char *str1, char *str2);
程序例:

#include
#include
#include

int main(void)
{
    char *string1 = "1234567890";
    char *string2 = "747DC8";
    int length;

    length = strcspn(string1, string2);
    printf("Character where strings intersect is at position %d\n", length);

    return 0;
}

函数名: strdup
功 能: 将串拷贝到新建的位置处
用 法: char *strdup(char *str);
程序例:

#include
#include
#include

int main(void)
{
    char *dup_str, *string = "abcde";

    dup_str = strdup(string);
    printf("%s\n", dup_str);
    free(dup_str);

    return 0;
}

函数名: stricmp
功 能: 以大小写不敏感方式比较两个串
用 法: int stricmp(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
   char *buf1 = "BBB", *buf2 = "bbb";
   int ptr;

   ptr = stricmp(buf2, buf1);

   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1\n");

   if (ptr < 0)
      printf("buffer 2 is less than buffer 1\n");

   if (ptr == 0)
      printf("buffer 2 equals buffer 1\n");

   return 0;
}

函数名: strerror
功 能: 返回指向错误信息字符串的指针
用 法: char *strerror(int errnum);
程序例:

#include
#include

int main(void)
{
   char *buffer;
   buffer = strerror(errno);
   printf("Error: %s\n", buffer);
   return 0;
}

函数名: strcmpi
功 能: 将一个串与另一个比较, 不管大小写
用 法: int strcmpi(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
   char *buf1 = "BBB", *buf2 = "bbb";
   int ptr;

   ptr = strcmpi(buf2, buf1);

   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1\n");

   if (ptr < 0)
      printf("buffer 2 is less than buffer 1\n");

   if (ptr == 0)
      printf("buffer 2 equals buffer 1\n");

   return 0;
}

函数名: strncmp
功 能: 串比较
用 法: int strncmp(char *str1, char *str2, int maxlen);
程序例:

#include
#include

int main(void)

{
   char *buf1 = "aaabbb", *buf2 = "bbbccc", *buf3 = "ccc";
   int ptr;

   ptr = strncmp(buf2,buf1,3);
   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1\n");
   else
      printf("buffer 2 is less than buffer 1\n");

   ptr = strncmp(buf2,buf3,3);
   if (ptr > 0)
      printf("buffer 2 is greater than buffer 3\n");
   else
      printf("buffer 2 is less than buffer 3\n");

   return(0);
}

函数名: strncmpi
功 能: 把串中的一部分与另一串中的一部分比较, 不管大小写
用 法: int strncmpi(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
   char *buf1 = "BBBccc", *buf2 = "bbbccc";
   int ptr;

   ptr = strncmpi(buf2,buf1,3);

   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1\n");

   if (ptr < 0)
      printf("buffer 2 is less than buffer 1\n");

   if (ptr == 0)
      printf("buffer 2 equals buffer 1\n");

   return 0;
}

函数名: strncpy
功 能: 串拷贝
用 法: char *strncpy(char *destin, char *source, int maxlen);
程序例:

#include
#include

int main(void)
{
   char string[10];
   char *str1 = "abcdefghi";

   strncpy(string, str1, 3);
   string[3] = '\0';
   printf("%s\n", string);
   return 0;
}

函数名: strnicmp
功 能: 不注重大小写地比较两个串
用 法: int strnicmp(char *str1, char *str2, unsigned maxlen);
程序例:

#include
#include

int main(void)
{
   char *buf1 = "BBBccc", *buf2 = "bbbccc";
   int ptr;

   ptr = strnicmp(buf2, buf1, 3);

   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1\n");

   if (ptr < 0)
      printf("buffer 2 is less than buffer 1\n");

   if (ptr == 0)
      printf("buffer 2 equals buffer 1\n");

   return 0;
}

 

函数名: strnset
功 能: 将一个串中的所有字符都设为指定字符
用 法: char *strnset(char *str, char ch, unsigned n);
程序例:

#include
#include

int main(void)
{
   char string[50] = "abcdefghijklmnopqrstuvwxyz";
   char letter = 'x';

   printf("string before strnset: %s\n", string);
   strnset(string, letter, 13);
   printf("string after strnset: %s\n", string);

   return 0;
}

函数名: strpbrk
功 能: 在串中查找给定字符集中的字符
用 法: char *strpbrk(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
   char *string1 = "abcdefghijklmnopqrstuvwxyz";
   char *string2 = "onm";
   char *ptr;

   ptr = strpbrk(string1, string2);

   if (ptr)
      printf("strpbrk found first character: %c\n", *ptr);
   else
      printf("strpbrk didn't find character in set\n");

   return 0;
}

函数名: strrchr
功 能: 在串中查找指定字符的最后一个出现
用 法: char *strrchr(char *str, char c);
程序例:

#include
#include

int main(void)
{
   char string[15];
   char *ptr, c = 'r';

   strcpy(string, "This is a string");
   ptr = strrchr(string, c);
   if (ptr)
      printf("The character %c is at position: %d\n", c, ptr-string);
   else
      printf("The character was not found\n");
   return 0;
}

函数名: strrev
功 能: 串倒转
用 法: char *strrev(char *str);
程序例:

#include
#include

int main(void)
{
   char *forward = "string";

   printf("Before strrev(): %s\n", forward);
   strrev(forward);
   printf("After strrev(): %s\n", forward);
   return 0;
}

函数名: strset
功 能: 将一个串中的所有字符都设为指定字符
用 法: char *strset(char *str, char c);
程序例:

#include
#include

int main(void)
{
   char string[10] = "123456789";
   char symbol = 'c';

   printf("Before strset(): %s\n", string);
   strset(string, symbol);
   printf("After strset(): %s\n", string);
   return 0;
}

函数名: strspn
功 能: 在串中查找指定字符集的子集的第一次出现
用 法: int strspn(char *str1, char *str2);
程序例:

#include
#include
#include

int main(void)
{
   char *string1 = "1234567890";
   char *string2 = "123DC8";
   int length;

   length = strspn(string1, string2);
   printf("Character where strings differ is at position %d\n", length);
   return 0;
}

函数名: strtod
功 能: 将字符串转换为double型值
用 法: double strtod(char *str, char **endptr);
程序例:

#include
#include

int main(void)
{
   char input[80], *endptr;
   double value;

   printf("Enter a floating point number:");
   gets(input);
   value = strtod(input, &endptr);
   printf("The string is %s the number is %lf\n", input, value);
   return 0;
}

函数名: strtok
功 能: 查找由在第二个串中指定的分界符分隔开的单词
用 法: char *strtok(char *str1, char *str2);
程序例:

#include
#include

int main(void)
{
   char input[16] = "abc,d";
   char *p;

  
   p = strtok(input, ",");
   if (p)   printf("%s\n", p);

  
   p = strtok(NULL, ",");
   if (p)   printf("%s\n", p);
   return 0;
}

函数名: strtol
功 能: 将串转换为长整数
用 法: long strtol(char *str, char **endptr, int base);
程序例:

#include
#include

int main(void)
{
   char *string = "87654321", *endptr;
   long lnumber;

  
   lnumber = strtol(string, &endptr, 10);
   printf("string = %s long = %ld\n", string, lnumber);

   return 0;
}

函数名: strupr
功 能: 将串中的小写字母转换为大写字母
用 法: char *strupr(char *str);
程序例:

#include
#include

int main(void)
{
   char *string = "abcdefghijklmnopqrstuvwxyz", *ptr;

  
   ptr = strupr(string);
   printf("%s\n", ptr);
   return 0;
}

 

函数名: swab
功 能: 交换字节
用 法: void swab (char *from, char *to, int nbytes);
程序例:

#include
#include
#include

char source[15] = "rFna koBlrna d";
char target[15];

int main(void)
{
   swab(source, target, strlen(source));
   printf("This is target: %s\n", target);
   return 0;
原型：extern char *strstr(char *haystack, char *needle);

所在头文件：#include

功能：从字符串haystack中寻找needle第一次出现的位置（不比较结束符NULL)。

说明：返回指向第一次出现needle位置的指针，如果没找到则返回NULL。

具体使用例子：

#include
#include
int main(int argc,char **argv)
{
char *haystack="aaa||a||bbb||c||ee||";
char *needle="||";
char* buf = strstr( haystack, needle);
while( buf != NULL )
{
buf[0]='\0';
printf( "%s\n ", haystack);
haystack = buf + strlen(needle);
buf = strstr( haystack, needle);
}
   return 0;
}