程序pipe, 它使用可例如： ./pipe who sort ./pipe ls head
1 /* pipe.c 2 * Demostrates how to create a pipeline from one process to another 3 * * take two args, each a command ,and connects 4 * argv[1]s output to intput of argv[2] 5 * effect: command1 | command2 6 */ 7 #include <stdio.h> 8 #include <unistd.h> 9 10 #define oops(x,n) { perror(x); exit(n); } 11 12 int main(int argc, char *argv[]){ 13 int pid, thepipe[2]; 14 if(argc!=3) { 15 fprintf(stderr, "usage: pipe cmd1 cmd2. "); 16 exit(1); 17 } 18 if(pipe(thepipe) == -1) 19 oops("pipe", 2); 20 if((pid=fork()) == -1) 21 oops("fork", 3); 22 if(pid==0) { /*child execs argv[1] and writes into pipe*/ 23 close(thepipe[0]); /* child doesnt read from pipe */ 24 if((dup2(thepipe[1], 1)) == -1) /*child change the stdout, set the stdout into the pipe*/ 25 oops(argv[1], 6); 26 close(thepipe[1]); /*stdout is duped , close pipe*/ 27 execlp(argv[1], argv[1], NULL); 28 oops("child", 4); 29 }else if(pid>0) { /*parent execs argv[0] and read from pipe*/ 30 close(thepipe[1]); /* parent doesnt write to pipe */ 31 if(dup2(thepipe[0], 0) == -1) 32 oops("could not redirect stdin", 6); 33 close(thepipe[0]); /* stdin is duped, close pipe */ 34 execlp(argv[2],argv[2], NULL); 35 oops(argv[2], 5); 36 } 37 return 0; 38 }