nix-shell output

[swflint@curry] git:(master 2↑) 1M~/bin% nix-shell -p xlibs.libXScrnSaver

[nix-shell:~/bin]$ cat x11idle.c
#include <X11/extensions/scrnsaver.h>
#include <stdio.h>

/* Based on code from
 * http://coderrr.wordpress.com/2008/04/20/getting-idle-time-in-unix/
 *
 * compile with 'gcc -l Xss x11idle.c -o x11idle' and copy x11idle into your
 * path
 */

int main() {
    XScreenSaverInfo *info = XScreenSaverAllocInfo();
    //open the display specified by the DISPLAY environment variable
    Display *display = XOpenDisplay(0);

    //display could be null if there is no X server running
    if (info == NULL || display == NULL) {
    return -1;
    }

    //X11 is running, try to retrieve info
    if (XScreenSaverQueryInfo(display, DefaultRootWindow(display), info) == 0) {
	return -1;
    }

    //info was retrieved successfully, print idle time
    printf("%lu\n", info->idle);
    return 0;
}

[nix-shell:~/bin]$ gcc -l xSS x11idle.c -o x11idle
x11idle.c:1:38: fatal error: X11/extensions/scrnsaver.h: No such file or directory
compilation terminated.

[nix-shell:~/bin]$