c语言字符函数

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[];
   char *str1 = "abcdefghi";
   stpcpy(string, str1);
   printf("%sn", string);
   return ;
} 

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[];
   char *blank = " ", *c = "C++", *Borland = "Borland";
   strcpy(destination, Borland);
   strcat(destination, blank);
   strcat(destination, c);
   printf("%sn", destination);
   return ;
} 

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[];
    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 ;
 } 

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 > )
       printf("buffer 2 is greater than buffer 1n");
    else
       printf("buffer 2 is less than buffer 1n");
    ptr = strcmp(buf2, buf3);
    if (ptr > )
       printf("buffer 2 is greater than buffer 3n");
    else
       printf("buffer 2 is less than buffer 3n");
    return ;
 }
  

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 > )
      printf("buffer 2 is greater than buffer 1n");
   if (ptr < )
      printf("buffer 2 is less than buffer 1n");
   if (ptr == )
      printf("buffer 2 equals buffer 1n");
   return ;
} 

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[];
    char *str1 = "abcdefghi";
    strcpy(string, str1);
    printf("%sn", string);
    return ;
 } 

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 = "";
    char *string2 = "747DC8";
    int length;
    length = strcspn(string1, string2);
    printf("Character where strings intersect is at position %dn", length);
    return ;
 } 

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 ;
 } 

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 > )
      printf("buffer 2 is greater than buffer 1n");
   if (ptr < )
      printf("buffer 2 is less than buffer 1n");
   if (ptr == )
      printf("buffer 2 equals buffer 1n");
   return ;
} 

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 ;
} 

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 > )
      printf("buffer 2 is greater than buffer 1n");
   if (ptr < )
      printf("buffer 2 is less than buffer 1n");
   if (ptr == )
      printf("buffer 2 equals buffer 1n");
   return ;
} 

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,);
   if (ptr > )
      printf("buffer 2 is greater than buffer 1n");
   else
      printf("buffer 2 is less than buffer 1n");
   ptr = strncmp(buf2,buf3,);
   if (ptr > )
      printf("buffer 2 is greater than buffer 3n");
   else
      printf("buffer 2 is less than buffer 3n");
   return();
} 

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,);
   if (ptr > )
      printf("buffer 2 is greater than buffer 1n");
   if (ptr < )
      printf("buffer 2 is less than buffer 1n");
   if (ptr == )
      printf("buffer 2 equals buffer 1n");
   return ;
} 

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[];
   char *str1 = "abcdefghi";
   strncpy(string, str1, );
   string[] = '';
   printf("%sn", string);
   return ;
} 

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, );
   if (ptr > )
      printf("buffer 2 is greater than buffer 1n");
   if (ptr < )
      printf("buffer 2 is less than buffer 1n");
   if (ptr == )
      printf("buffer 2 equals buffer 1n");
   return ;
} 

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, );
   printf("string after  strnset: %sn", string);
   return ;
} 

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 ;
} 

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[];
   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 ;
} 

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 ;
} 

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[] = "";
   char symbol = 'c';
   printf("Before strset(): %sn", string);
   strset(string, symbol);
   printf("After strset():  %sn", string);
   return ;
} 

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 = "";
   char *string2 = "123DC8";
   int length;
   length = strspn(string1, string2);
   printf("Character where strings differ is at position %dn", length);
   return ;
} 

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 ;
} 

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[], *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 ;
}

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[] = "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 ;
} 

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 = "", *endptr;
   long lnumber;
   /* strtol converts string to long integer  */
   lnumber = strtol(string, &endptr, );
   printf("string = %s  long = %ldn", string, lnumber);
   return ;
} 

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 ;
} 

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[] = "rFna koBlrna d";
char target[];
int main(void)
{
   swab(source, target, strlen(source));
   printf("This is target: %sn", target);
   return ;
}