Archived: Output redirection and daemonization

[zeusy|Nemsis]

Redirect the output of a command to a file and detaches it from the parent process.

(Can be used to make an application continue running even after logout)

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


void usage(char *command) {
    printf("%s: outputfile command args\n", command);
    _exit(0);
}

int main(int argc, char *argv[], char *envp[]) {
    pid_t forxed;
    int fd, error;
    char **args = &argv[2];

    if (argc < 3)
        usage(argv[0]);

    if ((forxed = fork()) == 0) {
        /* Replace stderr and stdout
         * with our file's fd
         */
        fd = open(argv[1], O_APPEND | O_WRONLY);
        if (fd < 0)
            goto error;

        error = dup2(fd, 1) + dup2(fd, 2);
        
        if (error != 3)
            goto error;

        execvp(argv[2], args);
        
        goto error;
    } else {
        /* Kill the parent with
         * a fork >:). Only way
         * to semi-daemonize...
         */
        _exit(0);
    }    
error:
    perror("Error");
    _exit(1);
}