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#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
int main(int argc, char** argv) {
if (geteuid() != 0) {
fprintf(stderr, "run me as root!\n");
return 1;
}
argc--; // argv[0] is the program name
if (argc == 0) {
fprintf(stderr, "usage: %s /dev/lork\n", argv[0]);
return 1;
}
char* dev = argv[1];
const char* input = "test";
int fd;
ssize_t bytes;
fd = open(dev, O_RDWR);
if (-1 == fd) {
fprintf(stderr, "open() failed with code %d\n", errno);
return 1;
}
bytes = write(fd, input, strlen(input));
if (-1 == bytes) {
fprintf(stderr, "write() failed with code %d\n", errno);
return 1;
}
fprintf(stderr, "input \"%s\" to %s (%ld bytes succesful)\n", input, dev, bytes);
char buf[80];
bytes = read(fd, buf, 80);
if (-1 == bytes) {
fprintf(stderr, "read() failed with code %d\n", errno);
return 1;
}
fprintf(stderr, "output from %s: (%ld bytes)\n", dev, bytes);
if (bytes > 0) {
if (bytes < 80) buf[bytes] = '\0'; // null terminate string for printf
printf("%s\n", buf);
}
if (-1 == close(fd)) {
fprintf(stderr, "close() failed with code %d\n", errno);
return 1;
}
return 0;
}
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