字符串常用函数讲解及演示集合

字符串全复制

/* strcpy example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str1[]="Sample string";
  char str2[40];
  char str3[40];
  strcpy (str2,str1);
  strcpy (str3,"copy successful");
  printf ("str1: %s\nstr2: %s\nstr3: %s\n",str1,str2,str3);
  return 0;
}

str1：示例字符串
str2：示例字符串
str3：复制成功

字符串半复制

/* strncpy example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str1[]= "To be or not to be";
  char str2[40];
  char str3[40];

  /* copy to sized buffer (overflow safe): */
  strncpy ( str2, str1, sizeof(str2) );

  /* partial copy (only 5 chars): */
  strncpy ( str3, str2, 5 );
  str3[5] = '\0';   /* null character manually added */

  puts (str1);
  puts (str2);
  puts (str3);

  return 0;
}

To be or not to be
To be or not to be
To be

字符串连接

/* strcat example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str[80];
  strcpy (str,"these ");
  strcat (str,"strings ");
  strcat (str,"are ");
  strcat (str,"concatenated.");
  puts (str);
  return 0;
}

these strings are concatenated.

字符串按字节比较

/* memcmp example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char buffer1[] = "DWgaOtP12df0";
  char buffer2[] = "DWGAOTP12DF0";

  int n;

  n=memcmp ( buffer1, buffer2, sizeof(buffer1) );

  if (n>0) printf ("'%s' is greater than '%s'.\n",buffer1,buffer2);
  else if (n<0) printf ("'%s' is less than '%s'.\n",buffer1,buffer2);
  else printf ("'%s' is the same as '%s'.\n",buffer1,buffer2);

  return 0;
}

“DWgaOtP12df0”大于“DWGAOTP12DF0”。
因为DWgAOtp12Df0大于DWGAOTP12DF0，因为两个单词中的第一个不匹配字符分别是“g”和“G”，并且“g”（103）的计算结果大于“G”（71）。

返回值	表示
<0	两个内存块中不匹配的第一个字节在ptr1中的值低于ptr2中的值
0	两个内存块的内容相等
>0	两个内存块中不匹配的第一个字节在ptr1中的值大于在ptr2中的值

与strcmp不同，该函数在找到空字符后不会停止比较。

字符串长度计算

/* strlen example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char szInput[256]={'a','b','c'};
  printf ("The sentence entered is %u characters long.\n",(unsigned)strlen(szInput));
  return 0;
}

The sentence entered is 3 characters long.

strlen()返回值是字符串长度，而非数组下标

字符匹配

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

int main ()
{
  char str[] = "This is a sample string";
  char * pch;
  printf ("Looking for the 's' character in \"%s\"...\n",str);
  pch=strchr(str,'s');
  while (pch!=NULL)
  {
    printf ("found at %d\n",pch-str+1);
    pch=strchr(pch+1,'s')
    /*从pch开始往后找，找到‘s’第一次出现的位置 若找不到，返回空指针*/
    /*位置从1开始计算*/
  }
  return 0;
}

Looking for the ‘s’ character in “This is a sample string”…
found at 4
found at 7
found at 11
found at 18

字符串匹配

/* strstr example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str[] ="This is a simple string";
  char * pch;
  pch = strstr (str,"simple");
  if (pch != NULL)
    strncpy (pch,"sample",6);
  puts (str);
  return 0;
}

This is a sample string

此示例在str中 搜索“simple”子字符串并将该单词替换为“sample”。
若需要匹配多次，可类比《字符匹配》

参考资料

http://www.cplusplus.com/reference/string/