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#if 0
cc -Wall -Wextra -pedantic $@ -o $(dirname $0)/bri $0 && \
sudo chown root:root $(dirname $0)/bri && \
sudo chmod u+s $(dirname $0)/bri
exit
#endif
// Backlight brightness control.
#include <dirent.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>
static const char *CLASS = "/sys/class/backlight";
int main(int argc, char *argv[]) {
int error;
if (argc < 2) errx(EX_USAGE, "usage: bri N | +... | -...");
error = chdir(CLASS);
if (error) err(EX_IOERR, "%s", CLASS);
DIR *dir = opendir(".");
if (!dir) err(EX_IOERR, "%s", CLASS);
struct dirent *entry;
while (NULL != (errno = 0, entry = readdir(dir))) {
if (entry->d_name[0] == '.') continue;
error = chdir(entry->d_name);
if (error) err(EX_IOERR, "%s", entry->d_name);
break;
}
if (!entry) {
if (errno) err(EX_IOERR, "%s", CLASS);
errx(EX_CONFIG, "empty %s", CLASS);
}
char *value = argv[1];
if (value[0] == '+' || value[0] == '-') {
FILE *actual = fopen("actual_brightness", "r");
if (!actual) err(EX_IOERR, "actual_brightness");
unsigned int brightness;
int match = fscanf(actual, "%u", &brightness);
if (match == EOF) err(EX_IOERR, "actual_brightness");
if (match < 1) err(EX_DATAERR, "actual_brightness");
size_t count = strnlen(value, 15);
if (value[0] == '+') {
brightness += 16 * count;
} else {
brightness -= 16 * count;
}
char buf[15];
snprintf(buf, sizeof(buf), "%u", brightness);
value = buf;
}
error = setuid(0);
if (error) err(EX_NOPERM, "setuid(0)");
FILE *brightness = fopen("brightness", "w");
if (!brightness) err(EX_IOERR, "brightness");
int count = fprintf(brightness, "%s", value);
if (count < 0) err(EX_IOERR, "brightness");
return EX_OK;
}
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