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/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
*
* Copyright (C) 2018 Benjamin Berg <bberg@redhat.com>
*
* Licensed under the GNU General Public License Version 2
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "config.h"
#include <stdlib.h>
#include <dirent.h>
#include <errno.h>
#include <string.h>
#include <libgen.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#define GSD_BACKLIGHT_HELPER_EXIT_CODE_SUCCESS 0
#define GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED 1
#define GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID 3
#define GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER 4
#ifndef __linux__
#error "gsd-backlight-helper does not work on non-Linux"
#endif
static void
usage(int argc, char *argv[])
{
fprintf (stderr, "Usage: %s device brightness\n", argv[0]);
fprintf (stderr, " device: The backlight directory starting with \"/sys/class/backlight/\"\n");
fprintf (stderr, " brightness: The new brightness to write\n");
}
int
main (int argc, char *argv[])
{
char tmp[512];
char *device = NULL;
int fd, len, res;
int uid, euid;
int brightness;
int result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
DIR *dp = NULL;
struct dirent *ep;
/* check calling UID */
uid = getuid ();
euid = geteuid ();
if (uid != 0 || euid != 0) {
fprintf (stderr, "This program can only be used by the root user\n");
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER;
goto done;
}
if (argc != 3) {
fprintf (stderr, "Error: Need to be called with exactly two arguments\n");
usage (argc, argv);
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID;
goto done;
}
errno = 0;
brightness = strtol (argv[2], NULL, 0);
if (errno) {
fprintf (stderr, "Error: Invalid brightness argument (%d: %s)\n", errno, strerror (errno));
usage (argc, argv);
goto done;
}
device = realpath (argv[1], NULL);
if (device == NULL) {
fprintf (stderr, "Error: Could not canonicalize given path (%d: %s)\n", errno, strerror (errno));
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
goto done;
}
dp = opendir ("/sys/class/backlight");
if (dp == NULL) {
fprintf (stderr, "Error: Could not open /sys/class/backlight (%d: %s)\n", errno, strerror (errno));
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
goto done;
}
while ((ep = readdir (dp))) {
char *path;
if (ep->d_name[0] == '.')
continue;
/* Leave room for "/brightness" */
snprintf (tmp, sizeof(tmp) - 11, "/sys/class/backlight/%s", ep->d_name);
path = realpath (tmp, NULL);
if (strcmp (path, device) == 0) {
free (path);
strcat (tmp, "/brightness");
fd = open (tmp, O_WRONLY);
if (fd < 0) {
fprintf (stderr, "Error: Could not open brightness sysfs file (%d: %s)\n", errno, strerror(errno));
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
goto done;
}
len = snprintf (tmp, sizeof(tmp), "%d", brightness);
if ((res = write (fd, tmp, len)) != len) {
if (res == -1)
fprintf (stderr, "Error: Writing to file (%d: %s)\n", errno, strerror(errno));
else
fprintf (stderr, "Error: Wrote the wrong length (%d of %d bytes)!\n", res, len);
close (fd);
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
goto done;
}
close (fd);
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_SUCCESS;
goto done;
} else {
free (path);
}
}
result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
fprintf (stderr, "Error: Could not find the specified backlight \"%s\"\n", argv[1]);
done:
if (device)
free (device);
if (dp)
closedir (dp);
return result;
}
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