pipe and redirect implement

0.pipe_and_redirect

.

foo

foo
bar

pipe.c

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

int main()
{
    int pipefd[2];
    int pid;

    char *cat_args[] = {"cat", "in", NULL};
    char *grep_args[] = {"grep", "foo", NULL};

    pipe(pipefd);

    pid = fork();

    if (pid == 0)
    {
        dup2(pipefd[0], STDIN_FILENO);
        close(pipefd[1]);

        execvp("grep", grep_args);
    }
    else
    {
        dup2(pipefd[1], STDOUT_FILENO);
        close(pipefd[0]);

        execvp("cat", cat_args);
    }
}

redirect.c

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

int main()
{
    int in, out;
    char *grep_args[] = {"grep", "foo", NULL};

    in = open("in", O_RDONLY);
    out = open("out", O_WRONLY | O_CREAT, S_IRUSR | S_IRGRP | S_IWGRP | S_IWUSR);

    dup2(in, STDIN_FILENO);
    dup2(out, STDOUT_FILENO);

    close(in);
    close(out);

    execvp("grep", grep_args);
}