Question

我对此问题有一个跟进问题：Classic C. Using pipes in execvp function, stdin and stdout redirection

我需要做同样的事情，但是有两个以上的命令。如果我执行ls | head | wc它不起作用。

我的方法是，第一个和最后一个之间的所有命令都需要从管道输入并将其输出到管道。我的代码如下所示：

if(i != 0 && i < notoken - 1) {
            close(STDOUT_FILENO);  //closing stdout
            dup(pipefd[1]);         //replacing stdout with pipe write 
            close(STDIN_FILENO);   //closing stdin
            dup(pipefd[0]);         //replacing stdin with pipe read
            close(pipefd[0]);       //closing pipe read
            close(pipefd[1]);

            argv[0] = token[i];
            argv[1] = NULL;
            execvp(argv[0], argv);
            perror("failed");
            exit(1);
    } else if(i == 0 && notoken > 1) {
        if(fork() == 0) {          //first fork
            close(STDOUT_FILENO);  //closing stdout
            dup(pipefd[1]);         //replacing stdout with pipe write 
            close(pipefd[0]);       //closing pipe read
            close(pipefd[1]);

            argv[0] = token[i];
            argv[1] = NULL;
            execvp(argv[0], argv);
            perror("failed");
            exit(1);
        }
    } else {
        if(fork() ==0) {
            close(STDIN_FILENO);   //closing stdin
            dup(pipefd[0]);         //replacing stdin with pipe read
            close(pipefd[1]);       //closing pipe write
            close(pipefd[0]);

            argv[0] = token[i];
            argv[1] = NULL;
            execvp(argv[0], argv);
            perror("failed");
            exit(1);
        }
    }

经典C.使用execvp和管道。重定向stdin和sdout

0 个答案: