C字符串操作

C字符串操作（转）

注：文中的几个大小写不敏感比较函数，原文用的是stricmp等，后来发现linux的std库没有，改为strcasecmp系列。

函数名: strcpy
功 能: 拷贝一个字符串到另一个字符串
用 法: char *strcpy(char *destin, char *source);
程序例: 
＃i nclude <stdio.h> 
＃i nclude <string.h> 
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: 
＃i nclude <string.h>
＃i nclude <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;
   }       
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: 
＃i nclude <string.h> ＃i nclude <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;
}       
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: 
＃i nclude <string.h>
＃i nclude <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;
}       
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: 
＃i nclude <string.h>
＃i nclude <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;
   }       
函数名: strcpy 
功 能: 串拷贝 
用 法: char *strcpy(char *str1, char *str2);
程序例: 
＃i nclude <stdio.h>
＃i nclude <string.h> 
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: 
＃i nclude <stdio.h> 
＃i nclude <string.h>
＃i nclude <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;
}       
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: 
＃i nclude <stdio.h>
＃i nclude <string.h>
＃i nclude <alloc.h> 
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: strcasecmp
功 能: 以大小写不敏感方式比较两个串 
用 法: int strcasecmp(char *str1, char *str2); 
程序例: 
＃i nclude <string.h>
＃i nclude <stdio.h> 
int main(void) 
{   
   char *buf1 = "BBB", *buf2 = "bbb";
   int ptr; 
   ptr = strcasecmp(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: 
＃i nclude <stdio.h> 
＃i nclude <errno.h> 
int main(void) 
{   
char *buffer;    
buffer = strerror(errno);    
printf("Error: %s/n", buffer);    
return 0; 
}       
函数名: strcasecmp 
功 能: 将一个串与另一个比较, 不管大小写
用 法: int strcasecmp(char *str1, char *str2); 
程序例: 
＃i nclude <string.h>
＃i nclude <stdio.h> 
int main(void)
{    
   char *buf1 = "BBB", *buf2 = "bbb";
   int ptr; 
   ptr = strcasecmp(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: 
＃i nclude <string.h>
＃i nclude <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);
   }     
函数名: strncasecmp 
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 strncasecmp(char *str1, char *str2); 
程序例: 
＃i nclude <string.h>
＃i nclude <stdio.h> 
int main(void) 
{
   char *buf1 = "BBBccc", *buf2 = "bbbccc";
   int ptr; 
   ptr = strncasecmp(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: 
＃i nclude <stdio.h>
＃i nclude <string.h> 
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: 
＃i nclude <string.h> 
＃i nclude <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; 
}       
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: 
＃i nclude <stdio.h>
＃i nclude <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; 
}     
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: 
＃i nclude <stdio.h> 
＃i nclude <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;
}       
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: 
＃i nclude <string.h> 
＃i nclude <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; 
}       
函数名: strrev 
功 能: 串倒转 
用 法: char *strrev(char *str);
程序例: 
＃i nclude <string.h>
＃i nclude <stdio.h> 
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: 
＃i nclude <stdio.h> 
＃i nclude <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; 
}       
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: 
＃i nclude <stdio.h>
＃i nclude <string.h>
＃i nclude <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; 
}     
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: 
＃i nclude <stdio.h> 
＃i nclude <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; }     
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: 
＃i nclude <stdio.h> 
＃i nclude <stdlib.h> 
int main(void) 
{
   char input[80], *endptr; 
   double ; 
   printf("Enter a floating point number:");
   gets(input);
   = strtod(input, &endptr); 
   printf("The string is %s the number is %lf/n", input, );
   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: 
＃i nclude <string.h> 
＃i nclude <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;
}       
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: 
＃i nclude <stdlib.h>
＃i nclude <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;
}   
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: 
＃i nclude <stdio.h>
＃i nclude <string.h> 
int main(void) 
{    
   char *string = "abcdefghijklmnopqrstuvwxyz", *ptr; 
   /* converts string to upper case characters */
   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: 
＃i nclude <stdlib.h> 
＃i nclude <stdio.h> 
＃i nclude <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; 
} 

from: http://www.yuanma.org/data/2006/1029/article_1738.htm