C语言字符串操作函数

1.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 <stdio.h> 
#include <string.h>

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

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

2.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 <string.h> 
#include <stdio.h>

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; 
} 
  
 3.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 <string.h> 
#include <stdio.h>

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; 
 } 
  
 4.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 <string.h> 
#include <stdio.h>

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; 
 }

5.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 <string.h> 
#include <stdio.h>

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; 
}

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

#include <stdio.h> 
#include <string.h>

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

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

7.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 <stdio.h> 
#include <string.h> 
#include <alloc.h>

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; 
 }

8.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 <stdio.h> 
#include <string.h> 
#include <alloc.h>

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

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

return 0; 
 }

9.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 <string.h> 
#include <stdio.h>

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; 
}

10.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 <stdio.h> 
#include <errno.h>

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

11.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 <string.h> 
#include <stdio.h>

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; 
}

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

#include <string.h> 
#include <stdio.h>

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); 
}

13.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 <string.h> 
#include <stdio.h>

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; 
}

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

#include <stdio.h> 
#include <string.h>

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

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

15.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 <string.h> 
#include <stdio.h>

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; 
}

16.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 <stdio.h> 
#include <string.h>

int main(void) 
{ 
   char *string = "abcdefghijklmnopqrstuvwxyz"; 
   char letter = 'x';

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

return 0; 
}

17.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 <stdio.h> 
#include <string.h>

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; 
}

18.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 <string.h> 
#include <stdio.h>

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; 
}

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

#include <string.h> 
#include <stdio.h>

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

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

20.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 <stdio.h> 
#include <string.h>

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; 
}

21.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 <stdio.h> 
#include <string.h> 
#include <alloc.h>

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; 
}

22.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 <stdio.h> 
#include <string.h>

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

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

23.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 <stdio.h> 
#include <stdlib.h>

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; 
}

24.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 <string.h> 
#include <stdio.h>

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

/* strtok places a NULL terminator 
   in front of the token, if found */ 
   p = strtok(input, ","); 
   if (p)   printf("%s\n", p);

/* A second call to strtok using a NULL 
   as the first parameter returns a pointer 
   to the character following the token  */ 
   p = strtok(NULL, ","); 
   if (p)   printf("%s\n", p); 
   return 0; 
}

25.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 <stdlib.h> 
#include <stdio.h>

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

/* strtol converts string to long integer  */ 
   lnumber = strtol(string, &endptr, 10); 
   printf("string = %s  long = %ld\n", string, lnumber);

return 0; 
}

26.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 <stdio.h> 
#include <string.h>

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

/* converts string to upper case characters */ 
   ptr = strupr(string); 
   printf("%s\n", ptr); 
   return 0; 
}

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

#include <stdlib.h> 
#include <stdio.h> 
#include <string.h>

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; 
}