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#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#define DBG 0
#if defined(__GNUC__) && (__GNUC__ > 3)
__attribute__((format(printf, 1, 2), noreturn))
#endif
static void die(const char *format, ...)
{
if (DBG) {
va_list args;
va_start(args, format);
vfprintf(stderr, format, args);
va_end(args);
}
exit(1);
}
int main(int argc, char *argv[])
{
struct stat st;
char buf[1024];
int len, fd;
if (argc != 2)
die("Usage: xf86-video-intel-backlight-helper <iface>\n");
if (strchr(argv[1], '/') != NULL)
die("Invalid interface '%s': contains '/'\n", argv[1]);
if (snprintf(buf, sizeof(buf),
"/sys/class/backlight/%s/brightness",
argv[1]) >= sizeof(buf))
die("Invalid interface '%s': name too long\n", argv[1]);
fd = open(buf, O_RDWR);
if (fd < 0 || fstat(fd, &st) || major(st.st_dev))
die("Invalid interface '%s': unknown backlight file\n", argv[1]);
while (fgets(buf, sizeof(buf), stdin)) {
len = strlen(buf);
if (write(fd, buf, len) != len)
die("Failed to update backlight interface '%s': errno=%d\n", argv[1], errno);
}
return 0;
}
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