[C] C中的字符串处理函数

轻舞飞扬SR

发布于 2021-02-24 10:48:42

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发布于 2021-02-24 10:48:42

函数名: strcpy 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("%sn", 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 <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("%sn", 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 <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: %dn", c, ptr-string); 
    else 
       printf("The character was not foundn"); 
    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 <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 1n"); 
    else 
       printf("buffer 2 is less than buffer 1n"); 
    ptr = strcmp(buf2, buf3); 
    if (ptr > 0) 
       printf("buffer 2 is greater than buffer 3n"); 
    else 
       printf("buffer 2 is less than buffer 3n"); 
    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 <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 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   return 0; 
}

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("%sn", 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 <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 %dn", 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 <stdio.h> 
#include <string.h> 
#include <alloc.h> 
int main(void) 
{ 
    char *dup_str, *string = "abcde"; 
    dup_str = strdup(string); 
    printf("%sn", dup_str); 
    free(dup_str); 
    return 0; 
}

函数名: strcmp 功能: 比较字符串str1和str2。用法: int strcmp(char *str1, char *str2); 说明: 当s1<s2时，返回值<0 　　当s1=s2时，返回值=0 　　当s1>s2时，返回值>0 　　即：两个字符串自左向右逐个字符相比（按ASCII值大小相比较），直到出现不同的字符或遇’\0’为止。程序例:

#include<stdio.h> 　　
#include<string.h> 　　
void main() 　　
{ 　　
    char string[20]; 　　
    char str[3][20]; 　　
    int i; 　　
    for(i=0;i<3;i++) 　　
    gets(str[i]); 　　
    if(strcmp(str[0],str[1])>0) 　　
    strcpy(string,str[0]); 　　
    else 　　
    strcpy(string,str[1]); 　　
    if(strcmp(str[2],string)>0) 　　
    strcpy(string,str[2]); 　　
    printf("\nThe largest string is %s\n",string); 　　
}

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 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   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 <stdio.h> 
#include <errno.h> 
int main(void) 
{ 
   char *buffer; 
   buffer = strerror(errno); 
   printf("Error: %sn", 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 <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 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   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 <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 1n"); 
   else 
      printf("buffer 2 is less than buffer 1n"); 
   ptr = strncmp(buf2,buf3,3); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 3n"); 
   else 
      printf("buffer 2 is less than buffer 3n"); 
   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 <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 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   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 <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char string[10]; 
   char *str1 = "abcdefghi"; 
   strncpy(string, str1, 3); 
   string[3] = ''; 
   printf("%sn", 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 <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 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   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 <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *string = "abcdefghijklmnopqrstuvwxyz"; 
   char letter = 'x'; 
   printf("string before strnset: %sn", string); 
   strnset(string, letter, 13); 
   printf("string after  strnset: %sn", 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 <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: %cn", *ptr); 
   else 
      printf("strpbrk didn't find character in setn"); 
   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 <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: %dn", c, ptr-string); 
   else 
      printf("The character was not foundn"); 
   return 0; 
}

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(): %sn", forward); 
   strrev(forward); 
   printf("After strrev():  %sn", 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 <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char string[10] = "123456789"; 
   char symbol = 'c'; 
   printf("Before strset(): %sn", string); 
   strset(string, symbol); 
   printf("After strset():  %sn", 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 <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 %dn", 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:

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *str1 = "Borland International", *str2 = "nation", *ptr; 
   ptr = strstr(str1, str2); 
   printf("The substring is: %sn", 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:

#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 %lfn", input, value); 
   return 0; 
}

函数名: strsep 功能: 分解字符串为一组字符串。从str1指向的位置起向后扫描，遇到delim指向位置的字符后，将此字符替换为NULL，返回str1指向的地址。用法: char *strtok(char **str1, const char *delim); 程序例:

int main() 　　
{ 　
　int len, nel; 　
　char query[] ="user_command=appleboy&test=1&test2=2"; 　
　char *q, *name, *value; 　　/* Parse into individualassignments */ 　
　q = query; 　　fprintf(stderr, "CGI[query string] : %s\n",query); 　
　len = strlen(query); 　
　nel = 1; 　
　while (strsep(&q, "&")) 　
　nel++; 　
　fprintf(stderr, "CGI[nel string] : %d\n", nel); 　
　for (q = query; q< (query + len);) 
   { 　
　    value = name = q; 　　/* Skip to next assignment */ 
　　fprintf(stderr, "CGI[string] :%s\n", q); 
　　fprintf(stderr, "CGI[stringlen] : %d\n", strlen(q)); 
　　fprintf(stderr, "CGI[address] :%x\n", q); 
　　for (q += strlen(q); q < (query +len) && !*q; q++); 　　/* Assign variable */ 
　　name = strsep(&value,"="); 
　　fprintf(stderr, "CGI[name ] :%s\n", name); 
　　fprintf(stderr, "CGI[value] :%s\n", 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 <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("%sn", 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("%sn", 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 <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 = %ldn", 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 <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *string = "abcdefghijklmnopqrstuvwxyz", *ptr; 
   /* converts string to upper case characters */ 
   ptr = strupr(string); 
   printf("%sn", 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 <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: %sn", target); 
   return 0; 
}

PS: isalpha()是字符函数，不是字符串函数， isalpha 原型：extern int isalpha(int c); 用法：#include <ctype.h> 功能：判断字符c是否为英文字母说明：当c为英文字母a-z或A-Z时，返回非零值，否则返回零。举例：

      // isalpha.c
      
      #include <syslib.h>
      #include <ctype.h>
      #include <stdio.h>

      main()
      {
        int c;
        
        clrscr();        // clear screen
        printf("Press a key");
        for(;;)
        {
          c=getchar();
          clrscr();
          printf("%c: %s letter",c,isalpha(c)?"is":"not");
        }
        return 0; // just to avoid warnings by compiler

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原始发表：2015/08/06 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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[C] C中的字符串处理函数

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