initiated commitment

.gitignore

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+**/*.o
+sbl*
+tests/**
+!**/*.c
+!**/*.1
+

LICENSE

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+               GLWT(Good Luck With That) Public License
+                 Copyright (c) Everyone, except Author
+
+Everyone is permitted to copy, distribute, modify, merge, sell, publish,
+sublicense or whatever they want with this software but at their OWN RISK.
+
+                            Preamble
+
+The author has absolutely no clue what the code in this project does.
+It might just work or not, there is no third option.
+
+
+                GOOD LUCK WITH THAT PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION, AND MODIFICATION
+
+  0. You just DO WHATEVER YOU WANT TO as long as you NEVER LEAVE A
+TRACE TO TRACK THE AUTHOR of the original product to blame for or hold
+responsible.
+
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
+Good luck and Godspeed.

README.md

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+# Simple backlight
+Simple utility to change the backlight
+
+## Features
+- Set the monitor to change
+- Save and restore backlight
+- Written in C99, that is a pro i guess...
+
+## Getting
+Clone this repository, then use `make` to compile, `make install` and `make
+uninstall` to install and uninstall, finally `make clean` to remove all the
+compiled junk from the folder.
+
+## Usage
+Here are some examples:
+
+```sh
+# Increase brightness by 10% and save the changed brightness to $HOME/.savefile
+$ sbl -c $HOME/.savefile -S -i 10
+# Set the brightness to 30%
+$ sbl -s 30
+# Restore the saved backlight value from example 1
+$ sbl -c $HOME/.savefile -r
+# Forgot what does what?
+$ sbl -h
+```
+Read the man page for detailed instructions

makefile

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+CC ?= gcc
+CFLAGS = -Wall -pedantic --std=c99 -O2
+PREFIX = /usr/local
+MANPREFIX = ${PREFIX}/share/man
+
+sbl: sbl.c
+
+dbg:
+	gcc -O0 -g sbl.c -o sbl-dbg
+
+install: sbl
+	mkdir -p ${DESTDIR}${PREFIX}/bin
+	cp -f sbl ${DESTDIR}${PREFIX}/bin/sbl
+	chown root:root ${DESTDIR}${PREFIX}/bin/sbl
+	chmod 4755 ${DESTDIR}${PREFIX}/bin/sbl
+	mkdir -p ${DESTDIR}${MANPREFIX}/man1
+	cp -f sbl.1 ${DESTDIR}${MANPREFIX}/man1/sbl.1
+	chmod 644 ${DESTDIR}${MANPREFIX}/man1/sbl.1
+
+uninstall:
+	rm -f ${DESTDIR}${PREFIX}/bin/sbl\
+		${DESTDIR}${MANPREFIX}/man1/sbl.1
+
+clean:
+	rm -f sbl sbl-dbg

sbl.c

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+#define _DEFAULT_SOURCE
+#define _POSIX_C_SOURCE 200809L
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <string.h>
+#include <wordexp.h>
+#include <limits.h>
+#include <getopt.h>
+#include <unistd.h>
+
+#define BACKLIGHT_ROOT_PATH "/sys/class/backlight/"
+#define BL_MIN 5
+
+#define const_arr_size(val) ((int)(sizeof(val)/sizeof(val[0])))
+
+const char *savefile_paths[] = {
+	NULL, /* reserved for external savefile path */
+	"/etc/sbl/savefile"
+};
+
+enum action {
+	DISPLAY, INCREASE, DECREASE, SET, RESTORE
+};
+
+static uid_t ruid;
+int device_index = 0;
+
+static void die (const char *, ...);
+static void usage (void);
+static void list_cards (void);
+static void set_brightness (float);
+static void change_permissions (const char *);
+static void restore_permissions (void);
+static int save_value (float);
+static int get_max_brightness (void);
+static float get_saved_value (void);
+static float get_current_brightness (void);
+static const char * backlight_path (int);
+static const char * get_savefile (void);
+
+int main (int argc, char *argv[])
+{
+	int opc = 0, store = 0;
+	enum action act = DISPLAY;
+	float value = BL_MIN;
+	char *extfile = NULL;
+	/* Parse command line arguments */
+	while ((opc = getopt(argc, argv, "c:hI:li:d:s:Sr")) != -1) {
+		switch (opc) {
+		case 'l':
+			list_cards();
+			break;
+		case 'h':
+			usage();
+			break;
+		case 'c':
+			extfile = malloc(strlen(optarg) + 1);
+			if (!extfile)
+				die("malloc in main():");
+			strcpy(extfile, optarg);
+			savefile_paths[0] = extfile;
+			break;
+		case 'I':
+			device_index = atoi(optarg);
+			break;
+		case 'i':
+			act = INCREASE;
+			value = atof(optarg);
+			break;
+		case 'd':
+			act = DECREASE;
+			value = atof(optarg);
+			break;
+		case 's':
+			act = SET;
+			value = atof(optarg);
+			break;
+		case 'r': 
+			act = RESTORE;
+			break;
+		case 'S':
+			store = 1;
+			break;
+		default:
+			exit(EXIT_FAILURE);
+			break;
+		}
+	}
+
+	ruid = getuid ();
+
+	switch (act) {
+		case DISPLAY:
+			printf("%.2f\n", get_current_brightness());
+			break;
+		case SET:
+			set_brightness(value);
+			break;
+		case INCREASE:
+			value += get_current_brightness();
+			set_brightness(value);
+			break;
+		case DECREASE:
+			value = get_current_brightness() - value;
+			set_brightness(value);
+			break;
+		case RESTORE:
+			set_brightness(get_saved_value());
+			break;
+		default:
+			break;
+	}
+
+	if (store)
+		save_value(get_current_brightness());
+
+	if (extfile)
+		free(extfile);
+	return 0;
+}
+
+int save_value (float value)
+{
+	FILE *fd;
+	fd = fopen(get_savefile(), "w");
+	if (!fd)
+		die("could not open savefile");
+	fprintf(fd, "%f\n", value);
+	fclose(fd);
+	return 1;
+}
+
+float get_saved_value (void)
+{
+	FILE *fd;
+	float rtf = -1;
+	fd = fopen(get_savefile(), "r");
+	if (!fd)
+		die("could not open savefile");
+	fscanf(fd, "%f", &rtf);
+	fclose(fd);
+	return rtf;
+}
+
+float get_current_brightness (void)
+{
+	FILE *fd;
+	char buf[PATH_MAX] = {0};
+	int cb = -1;
+	const char *path = backlight_path(device_index);
+	if (!path)
+		die("invalid device index"); 
+	strcpy(buf, path);
+	strcat(buf, "/brightness");
+	fd = fopen(buf, "r");
+	if (!fd)
+		die("could not open %s", buf);
+	fscanf(fd, "%d", &cb);
+	fclose(fd);
+ 
+	return ((float)cb / (float)get_max_brightness()) * 100.0;;
+}
+
+int get_max_brightness (void)
+{
+	FILE *fd;
+	char buf[PATH_MAX] = {0};
+	int rti = -1;
+	const char *path = backlight_path(device_index);
+	if (!path)
+		die("invalid device index"); 
+	strcpy(buf, path);
+	strcat(buf, "/max_brightness");
+	fd = fopen(buf, "r");
+	if (!fd)
+		die("could not open %s", buf);
+	fscanf(fd, "%d", &rti);
+	fclose(fd);
+
+	return rti;
+}
+
+/* Return the correct savefile path, creating it if it does not exist */
+const char * get_savefile (void)
+{
+	static char buf[PATH_MAX];
+	wordexp_t result = {0};
+	FILE *fd;
+
+	for (int i = 0; i < const_arr_size(savefile_paths); i++) {
+		if (!savefile_paths[i])
+			continue;
+		switch (wordexp(savefile_paths[i], &result, 0)) {
+		case 0:
+			break;
+		case WRDE_NOSPACE:
+			wordfree (&result);
+			die("Not enough space");
+		default:
+			die("Path not valid");
+		}
+
+		strcpy(buf, result.we_wordv[0]);
+		if ((fd = fopen(result.we_wordv[0], "r")))
+			break;
+	}
+	/* Create a savefile */
+	if (!fd) {
+		wordfree(&result);
+		for (int i = 0; i < const_arr_size(savefile_paths); i++) {
+			if (!savefile_paths[i])
+				continue;
+			switch (wordexp(savefile_paths[i], &result, 0)) {
+			case 0:
+				break;
+			case WRDE_NOSPACE:
+				wordfree (&result);
+				die("Not enough space");
+			default:
+				die("Path not valid");
+			}
+
+			strcpy(buf, result.we_wordv[0]);
+		if ((fd = fopen(result.we_wordv[0], "w")))
+			break;
+		}
+	}
+	wordfree(&result);
+	if (!fd)
+		die("could not open or create a savefile");
+	fclose(fd);
+	return buf;
+}	
+
+const char * backlight_path (int index)
+{
+	DIR *dp;
+	struct dirent *de;
+	static char buf[PATH_MAX];
+
+	memset(buf, 0, PATH_MAX);
+	if (index < 0)
+		die("%d is not a valid index", index);
+	if (!(dp = opendir(BACKLIGHT_ROOT_PATH)))
+		die("error opening " BACKLIGHT_ROOT_PATH);
+
+	errno = 0;
+	while ((de = readdir(dp))) {
+		if (!(de->d_type & DT_LNK))
+			continue;
+		if (index) {
+			index--;
+			continue;
+		} else {
+			strcpy(buf, BACKLIGHT_ROOT_PATH);
+			strcat(buf, de->d_name);
+			break;
+		}
+	}
+	closedir(dp);
+	if (errno)
+		die("error reading " BACKLIGHT_ROOT_PATH);
+	// FIXME: actually check return value of this
+	if (!buf[0])
+		return NULL;
+	return buf;
+
+}
+
+void list_cards (void)
+{
+	int i = 0;
+	const char *s;
+	for (; (s = backlight_path(i)); i++)
+		printf("%d: %s\n", i, s);
+	exit(EXIT_SUCCESS);
+}
+
+void set_brightness (float value)
+{
+	int set;
+	char buf[PATH_MAX] = {0};
+	const char *path = backlight_path(device_index);
+	FILE *fd;
+	if (value > 100)
+		value = 100;
+	if (value < BL_MIN)
+		value = BL_MIN;
+	set = (value/100.0) * get_max_brightness();
+	if (set < 0)
+		return;
+	if (!path)
+		die("invalid device index"); 
+	strcpy(buf, path);
+	strcat(buf, "/brightness");
+	change_permissions(buf);
+	fd = fopen(buf, "w");
+	if (!fd)
+		die("could not open %s", buf);
+	fprintf(fd, "%d", set);
+	fclose(fd);
+	restore_permissions();
+}
+
+/* Change the process permissions matching the ones pointed by path */
+void change_permissions (const char *path)
+{
+	int status;
+	struct stat st;
+
+	stat(path, &st);
+	status = seteuid(st.st_uid);
+	if (status < 0)
+		die("could not setuid");
+}
+
+static void restore_permissions (void)
+{
+	int status;
+	status = seteuid(ruid);
+	if (status < 0)
+		die("could not setuid");
+}
+
+void die(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+
+     	vfprintf(stderr, fmt, ap);
+
+	if (fmt[0] && fmt[strlen(fmt) - 1] == ':') {
+		fputc(' ', stderr);
+		perror(NULL);
+	} else {
+		fputc('\n', stderr);
+	}
+
+	va_end(ap);
+	exit(errno ? errno : 1);
+}
+
+static void usage (void)
+{
+	puts("Usage: sbl [-hlrS] [-c savefile] [-I index] [-i/d/s percent]\n"
+	     "-h              print this message\n"
+	     "-l              list devices by index\n"
+	     "-r              restore saved value\n"
+	     "-S              save value\n"
+	     "-c savefile     specify savefile\n"
+	     "-I index        specify device by index\n"
+	     "-i percent      increase backlight by percent\n"
+     	     "-d percent      decrease backlight by percent\n"
+	     "-s percent      set backlight to percent\n");
+	exit(EXIT_SUCCESS);
+}