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pipe()函式 Unix/Linux

pipe - 建立管道

內容簡介

#include <unistd.h>

int pipe(int filedes[2]);

描述

pipe() creates a pair of file descriptors, yiibaiing to a pipe inode, and places them in the array yiibaied to by filedes. filedes[0] is for reading, filedes[1] is for writing.

返回值

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

錯誤

標籤 描述
EFAULT filedes is not valid.
EMFILE Too many file descriptors are in use by the process.
ENFILE The system limit on the total number of open files has been reached.

遵循於

POSIX.1-2001.

範例

The following program creates a pipe, and then fork(2)s to create a child process. After the fork(2), each process closes the descriptors that it doesn’t need for the pipe (seepipe(7)). The parent then writes the string contained in the program’s command-line argument to the pipe, and the child reads this string a byte at a time from the pipe and echoes it on standard output. 

#include <sys/wait.h> 
#include <assert.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <string.h>

int
main(int argc, char *argv[])
{
    int pfd[2];
    pid_t cpid;
    char buf;

    assert(argc == 2);

    if (pipe(pfd) == -1) { perror("pipe"); exit(EXIT_FAILURE); }

    cpid = fork();
    if (cpid == -1) { perror("fork"); exit(EXIT_FAILURE); }


    if (cpid == 0) {    /* Child reads from pipe */
        close(pfd[1]);          /* Close unused write end */


        while (read(pfd[0], &buf, 1) > 0)
            write(STDOUT_FILENO, &buf, 1);


        write(STDOUT_FILENO, "
", 1);
        close(pfd[0]);
        _exit(EXIT_SUCCESS);


    } else {            /* Parent writes argv[1] to pipe */
        close(pfd[0]);          /* Close unused read end */
        write(pfd[1], argv[1], strlen(argv[1]));
        close(pfd[1]);          /* Reader will see EOF */
        wait(NULL);             /* Wait for child */
        exit(EXIT_SUCCESS);
    }
}
 

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