C字串操作

C字串操作（轉）註：文中的幾個大小寫不敏感比較函數，原文用的是stricmp等，後來發現linux的std庫沒有，改為strcasecmp系列。


函數名: strcpy
功 能: 拷貝一個字串到另一個字串
用 法: char *strcpy(char *destin, char *source);
程式例:
＃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;
}      
函數名: strcat
功 能: 字串拼接函數
用 法: char *strcat(char *destin, char *source);
程式例:
＃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;
   }      
函數名: strchr
功 能: 在一個串中尋找給定字元的第一個匹配之處/
用 法: char *strchr(char *str, char c);
程式例:
＃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;
}      
函數名: strcmp
功 能: 串比較
用 法: int strcmp(char *str1, char *str2);
看Asic碼，str1>str2，傳回值 > 0；兩串相等，返回0程式例:
＃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;
}      
函數名: strncmpi
功 能: 將一個串中的一部分與另一個串比較, 不管大小寫
用 法: int strncmpi(char *str1, char *str2, unsigned maxlen);
程式例:
＃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;
   }      
函數名: strcpy
功 能: 串拷貝
用 法: char *strcpy(char *str1, char *str2);
程式例:
＃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;
}      
函數名: strcspn
功 能: 在串中尋找第一個給定字元集內容的段
用 法: int strcspn(char *str1, char *str2);
程式例:
＃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;
}      
函數名: strdup
功 能: 將串拷貝到建立的位置處
用 法: char *strdup(char *str);
程式例:
＃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;
}      
函數名:
strcasecmp

功 能: 以大小寫不敏感方式比較兩個串
用 法: int
strcasecmp(char *str1, char *str2);
程式例:
＃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;
}    
函數名: strerror
功 能: 返回指向錯誤資訊字串的指標
用 法: char *strerror(int errnum);
程式例:
＃i nclude <stdio.h>
＃i nclude <errno.h>
int main(void)
{  
char *buffer;   
buffer = strerror(errno);   
printf("Error: %s/n", buffer);   
return 0;
}      
函數名:
strcasecmp
功 能: 將一個串與另一個比較, 不管大小寫
用 法: int
strcasecmp(char *str1, char *str2);
程式例:
＃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; }      
函數名: strncmp
功 能: 串比較
用 法: int strncmp(char *str1, char *str2, int maxlen);
程式例:
＃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);
   }    
函數名:
strncasecmp
功 能: 把串中的一部分與另一串中的一部分比較, 不管大小寫
用 法: int
strncasecmp(char *str1, char *str2);
程式例:
＃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;
   }    
函數名: strncpy
功 能: 串拷貝
用 法: char *strncpy(char *destin, char *source, int maxlen);
程式例:
＃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;
}    
函數名: strnicmp
功 能: 不注重大小寫地比較兩個串
用 法: int strnicmp(char *str1, char *str2, unsigned maxlen);
程式例:
＃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;
}      
函數名: strnset
功 能: 將一個串中的所有字元都設為指定字元
用 法: char *strnset(char *str, char ch, unsigned n);
程式例:
＃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;
}    
函數名: strpbrk
功 能: 在串中尋找給定字元集中的字元
用 法: char *strpbrk(char *str1, char *str2);
程式例:
＃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;
}      
函數名: strrchr
功 能: 在串中尋找指定字元的最後一個出現
用 法: char *strrchr(char *str, char c);
程式例:
＃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;
}      
函數名: strrev
功 能: 串倒轉
用 法: char *strrev(char *str);
程式例:
＃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;
}  
函數名: strset
功 能: 將一個串中的所有字元都設為指定字元
用 法: char *strset(char *str, char c);
程式例:
＃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;
}      
函數名: strspn
功 能: 在串中尋找指定字元集的子集的第一次出現
用 法: int strspn(char *str1, char *str2);
程式例:
＃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;
}    
函數名: strstr
功 能: 在串中尋找指定字串的第一次出現
用 法: char *strstr(char *str1, char *str2);
程式例:
＃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; }    
函數名: strtod
功 能: 將字串轉換為double型值
用 法: double strtod(char *str, char **endptr);
程式例:
＃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;
}      
函數名: strtok
功 能: 尋找由在第二個串中指定的分界符分隔開的單詞
用 法: char *strtok(char *str1, char *str2);
程式例:
＃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;
}      
函數名: strtol
功 能: 將串轉換為長整數
用 法: long strtol(char *str, char **endptr, int base);
程式例:
＃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;
}  
函數名: strupr
功 能: 將串中的小寫字母轉換為大寫字母
用 法: char *strupr(char *str);
程式例:
＃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;
}      
函數名: swab
功 能: 交換位元組
用 法: void swab (char *from, char *to, int nbytes);
程式例:
＃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