Linux_C 进程间共享管道

程序pipe, 它使用可例如： ./pipe who sort   ./pipe ls head

/* pipe.c
 * Demostrates how to create a pipeline from one process to another
 * * take two args, each a command ,and connects
 *   argv[1]s output to intput of argv[2]
 *   effect: command1 | command2
 */
#include <stdio.h>
#include <unistd.h>

#define oops(x,n) { perror(x); exit(n); }

int main(int argc, char *argv[]){
  int pid, thepipe[2];
  if(argc!=3) {
    fprintf(stderr, "usage: pipe cmd1 cmd2.
");
    exit(1);
  }
  if(pipe(thepipe) == -1)
    oops("pipe", 2);
  if((pid=fork()) == -1)
    oops("fork", 3);
  if(pid==0) {                  /*child execs argv[1] and writes into pipe*/
    close(thepipe[0]);          /*      child doesnt read from pipe       */
    if((dup2(thepipe[1], 1)) == -1)     /*child change the stdout, set the stdout into the pipe*/
      oops(argv[1], 6);
    close(thepipe[1]);          /*stdout is duped , close pipe*/
    execlp(argv[1], argv[1], NULL);
    oops("child", 4);
  }else if(pid>0) {             /*parent execs argv[0] and read from pipe*/
    close(thepipe[1]);          /*     parent doesnt write to pipe       */
    if(dup2(thepipe[0], 0) == -1)
      oops("could not redirect stdin", 6);
    close(thepipe[0]);          /*     stdin is duped, close pipe        */
    execlp(argv[2],argv[2], NULL);
    oops(argv[2], 5);
  }
  return 0;
}