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

void print_usage_info(const char *program);
int main(int argc, char **argv)
{

    if (argc != 2 + 1)
        print_usage_info(argv[0]);
    int pip[2][2]; /* Pipe 1: program1 -> program2 */
                   /* Pipe 2: program1 <- program2 */
    for (int i = 0; i < 2; ++i)
        pipe(pip[i]);
    /* Original process will execute 1st program, while other will take care about 2nd */
    if (fork()) {
        close(pip[0][0]);
        close(pip[1][1]);
        dup2(pip[1][0], 0);
        dup2(pip[0][1], 1);
        execl(argv[1], argv[1], NULL);
    } else {
        close(pip[0][1]);
        close(pip[1][0]);
        dup2(pip[0][0], 0);
        dup2(pip[1][1], 1);
        execl(argv[2], argv[2], NULL);
    }
    fprintf(stderr, "How did I got here: file %s, line %d\n", __FILE__, __LINE__);
    return -1;
}

void print_usage_info(const char *program)
{
    fprintf(stderr, "%s: incorrect arguments. Usage:\n%s program1 program2\n", program, program);
    exit(1);
}