Learning Linux IPC, part I Pipes

        #include <stdio.h>
        #include <unistd.h>
        #include <sys/types.h>
 
        main()
        {
                int     fd[2];
                pid_t   childpid;
 
                pipe(fd);
 
                if((childpid = fork()) == -1)
                {
                        perror("fork");
                        exit(1);
                }
 
                if(childpid == 0)
                {
                        /* Child process closes up input side of pipe */
                        close(fd[0]);
                }
                else
                {
                        /* Parent process closes up output side of pipe */
                        close(fd[1]);
                }
                .
                .
        }

#include <stdio.h>
 
int main(void)
{
        FILE *pipein_fp, *pipeout_fp;
        char readbuf[80];
 
        /* Create one way pipe line with call to popen() */
        if (( pipein_fp = popen("ls", "r")) == NULL)
        {
                perror("popen");
                exit(1);
        }
 
        /* Create one way pipe line with call to popen() */
        if (( pipeout_fp = popen("sort", "w")) == NULL)
        {
                perror("popen");
                exit(1);
        }
 
        /* Processing loop */
        while(fgets(readbuf, 80, pipein_fp))
                fputs(readbuf, pipeout_fp);
 
        /* Close the pipes */
        pclose(pipein_fp);
        pclose(pipeout_fp);
 
        return(0);
}