How does the ls command find the hard link count?

Question

How does the command ls -l count the number of hard links of an inode? Does it use the Linux API or is it code that requires deeper knowledge of the Linux kernel so

Answer 1

Here is a real simple program illustrating the user of stat() to find hard-link counts:

#include <stdio.h>
#include <sys/stat.h>

int main ( int argc, char ** argv ) {
    int     i;
    struct stat st;     /* stat puts info here */

    for (i = 1; i < argc; ++i) {
        if (stat(argv[i], &st) == -1) perror(argv[i]);
        else printf("%s has %d hard links\n", argv[i], st.st_nlink);
    }
    return 0;
}

(Pass it one or more file-names on the command line)

Answer 2

It calls stat to get information about the file (in a struct stat). Then it looks at the st_nlink field of the struct stat.