Print error message for specific X11 error code.

xlib_err.c

/**
 * xlib_err
 * print error message for specific error code
 *
 * (c) 2016 Bernd Busse
 **/

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <X11/Xlib.h>

int main(int argc, char* argv[]) {
    if (argc != 2) {
        fprintf(stderr, "usage: %s CODE\n", argv[0]);
        return EXIT_FAILURE;
    }

    Display* dpy = XOpenDisplay(NULL);
    if (dpy == NULL) {
        fprintf(stderr, "Error: cannot connect to X\n");
        return EXIT_FAILURE;
    }

    int code = atoi(argv[1]);
    char buf[256] = { 0 };

    XGetErrorText(dpy, code, buf, 256);
    printf("Error Code: %d\n", code);
    printf(" => %s\n", buf);

    return EXIT_SUCCESS;
}