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#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
int main(int argc, char *argv[])
{
struct stat st;
char buf[1024], *b = buf;
int len, fd;
if (argc != 2) {
fprintf(stderr, "Usage: %s <iface>\n", argv[0]);
return 1;
}
snprintf(buf, sizeof(buf), "/sys/class/backlight/%s/brightness", argv[1]);
fd = open(buf, O_RDWR);
if (fd < 0 || fstat(fd, &st) || major(st.st_dev)) {
fprintf(stderr, "Cannot access backlight interface '%s'\n", argv[1]);
return 1;
}
while ((len = read(0, b, sizeof(buf) - (b - buf) - 1)) > 0) {
len += b - buf;
buf[len] = '\0';
b = buf;
do {
char *end = strchr(b, '\n');
if (end == NULL)
break;
++end;
if (write(fd, b, end - b) != end - b) {
fprintf(stderr, "Failed to update backlight interface '%s'\n", argv[1]);
return 2;
}
b = end;
} while (1);
memmove(buf, b, len = buf + len - b);
b = buf + len;
}
return 0;
}
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