strcat, strncat - concatenate two strings


#include <string.h>

char *strcat(char *dest, const char *src);

char *strncat(char *dest, const char *src, size_t n);


The strcat() function appends the src string to the dest string, overwriting the null byte ('\0') at the end of dest, and then adds a terminating null byte. The strings may not overlap, and the dest string must have enough space for the result.

The strncat() function is similar, except that
* it will use at most n characters from src; and
* src does not need to be null terminated if it contains n or more characters.
As with strcat(), the resulting string in dest is always null terminated.

If src contains n or more characters, strncat() writes n+1 characters to dest (n from src plus the terminating null byte). Therefore, the size of dest must be at least strlen(dest)+n+1.

A simple implementation of strncat() might be:

char* strncat(char *dest, const char *src, size_t n) { size_t dest_len = strlen(dest); size_t i;

for (i = 0 ; i < n && src[i] != '\0' ; i++) dest[dest_len + i] = src[i]; dest[dest_len + i] = '\0';

return dest; }


The strcat() and strncat() functions return a pointer to the resulting string dest.


SVr4, 4.3BSD, C89, C99.


bcopy(3), memccpy(3), memcpy(3), strcpy(3), strncpy(3), wcscat(3), wcsncat(3)


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