strcat 和strncat 函数学习

函数原型

char * strcat ( char * destination, const char * source );

Concatenate strings连接字符串

Appends a copy of the source string to the destination string. The terminating null character in destination is overwritten by the first character of source, and a new null-character is appended at the end of the new string formed by the concatenation of both in destination.

将source的字符串连接到destination上，最后的null被覆盖，然后再最后加个null字符。

Parameters

destination

Pointer to the destination array, which should contain a C string, and be large enough to contain the concatenated resulting string.

source

C string to be appended. This should not overlap destination.

/* 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;
}

输出结果
these strings are concatenated.

strncat 指定长度的链接字符串。

Append characters from string

Appends the first num characters of source to destination, plus a terminating null-character. If the length of the C string in source is less than num, only the content up to the terminating null-character is copied.

Parameters

destination

Pointer to the destination array, which should contain a C string, and be large enough to contain the concatenated resulting string, including the additional null-character.

source

C string to be appended.

num

Maximum number of characters to be appended.

Return Value

destination is returned.

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

int main ()
{
  char str1[20];
  char str2[20];
  strcpy (str1,"To be ");
  strcpy (str2,"or not to be");
  strncat (str1, str2, 6);
  puts (str1);
  return 0;
}

Output:

To be or not