Linux getpwnam () library dependencies

I had a program, the system call was getpwnam()

not being executed at runtime. To debug this, I decided to run getpwnam()

in isolation with this code (it appeared on the forum):

#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
struct passwd *pw;

if (argc != 2) {
    printf("usage: %s username\n", argv[0]);
    exit(0);
}
pw = getpwnam(argv[1]);
if (pw == NULL)
    printf("getpwnam failed\n");
else
    printf("home dir = %s\n", pw->pw_dir);
    exit(0);
}

      

        
        
        
      

    

Oddly enough, it depends on the presence libnss_compat-2.3.5.so

:

With libnss_compat:

./pwnam root home dir = /root

Without libnss_compat:

./pwnam root getpwnam failed

So my question is; why getpwnam()

depends on libnss_compat*.so

? I found out with the command nm -D

what libc-2.3.5.so

is the lib that provides getpwnam()

.

readelf -d

shows that, libc

in turn, depends only on ld.so.1

. This, in turn, does not depend on anything. So why does it actually libnss_compat

have an impact?

Thanks for your help everyone!