Send an arbitrary series of 0's and 1's to a GPIO with given intervals between the level change (e.g. for sending a code over a 433 MHz sender)

gpio-send.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

int main(int argc, char **argv) {
    if(argc < 4 || argc % 2) {
        printf(
            "Usage: %s <path to GPIO value file> <interval 1> <interval 2> ... <interval n>\n\n"
            "Provide the path to the 'value' file of the GPIO in sysfs and an even number of intervals\n", argv[0]);
        return 1;
    }

    int fd = open(argv[1], O_WRONLY);
    if(fd == -1) {
        perror("open");
        return 1;
    }

    char *nums = "10";

    for(int j = 0; j < 5; j++) {
        for(int i = 0; i < argc - 2; i++) {
            if(write(fd, nums + (i % 2), 1) != 1) {
                perror("write");
                return 1;
            }
            usleep(atoi(argv[i+2]));
        }
    }

    if(close(fd)) {
        perror("close");
        return 1;
    }

    return 0;
}