In C, how does strlcat() work?

strlcat() is a function found in some implementations of the string.h library, but it is not a standard C function. To use this function, you must include this library:

#include <bsd/string.h>

And compile with the -lbsd option, for example:

clang-7 -pthread -lm -lbsd -o main main.c

Here is the prototype:

size_t strlcat( char *dst, const char *src, size_t size);

The function concatenates the strings dst and src, and places the result in the string dst. Unlike the strcat() function, strlcat() guarantees that the total length of the result string will be between the initial length of dst and size. The zero at the end of the string is included. This function is mainly used to avoid oversize of the character array. Let's consider the following strings:

char dst[100] = "1234";
char src[100] = "ABCD";

Here are some examples of strlcat():

// Retourne 8
// dst = 1234AB
// src = ABCD
strlcat(dst, src, 7);

// Retourne 6
// dst = 1234
// src = ABCD
strlcat(dst, src, 2)

Vous pouvez tester la fonction en ligne sur repl.it.