dev 69

# build: `gcc -o 69 69.c`
# insert as root: `./69`
# access: `cat /dev/69`
 
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
 
int daemon_init( void )
{
    pid_t pid;
 
    if ( ( pid = fork() ) < 0 )
    {
        return -1;
    }
    else if ( pid != 0 )
    {
        exit(0); /* parent exits */
    }
 
    setsid();
    chdir( "/dev" );
    umask(0);
 
    return 0;
}
 
void create_fifo( char* filename )
{
    if ( mknod( filename, S_IFIFO | 0600, 0 ) == -1 )
    {
        system( "mkfifo --mode=0600 /dev/69" );
    }
}
 
void check_fifo( char* filename )
{
    struct stat buf;
 
    if ( stat( filename, &buf ) == -1 )
    {
        create_fifo(filename);
        if ( stat( filename, &buf ) == -1 )
        {
            exit(EXIT_FAILURE);
        }
    }
 
    if ( !S_ISFIFO(buf.st_mode) )
    {
        if ( unlink(filename) == -1 )
        {
            exit(EXIT_FAILURE);
        }
        create_fifo(filename);
    }
}
 
void monitor_fifo( char* filename )
{
    while (1)
    {
 
        int fd;
 
        check_fifo(filename);
 
        if ( ( fd = open( filename, O_WRONLY ) ) == -1 )
        {
            exit(EXIT_FAILURE);
        }
 
        while (1)
        {
            write( fd, "69", strlen("69") );
        }
 
        (void) close(fd);
 
        sleep(1);  /* to avoid dup sigs */
    }
}
 
int main( int argc, char* argv[] )
{
    if ( daemon_init() )
    {
        fprintf( stderr, "%s: Error initializing daemon\n", argv[0] );
        return -1;
    }
 
    monitor_fifo("/dev/69");
 
    return 0;
}