试验目的：

1、向管道写端写入数据前，关闭管道写端fd，errno值会是什么？

2、向管道写端写入数据后，关闭管道写端fd，从管道读端读取数据时，是否能正常读取数据？

3、向管道写端写入数据后，关闭管道读端fd，从管道读端读取数据时，会发生什么？errno是什么？

4、向管道写端写入输入前，关闭管道读端fd，是否会触发SIGPIPE信号？程序如何不崩溃？errno值是否会为EPIPE？

1、创建一个管道pipefd[2]

2、向管道写端pipefd[1]写入数据

3、从管道读端pipefd[0]读取数据

4、正常关闭管道写端和读端

1、errno=8, 写端fd报：Bad file descriptor。不会触发SIGPIPE， errno也不会为EPIPE

2、可以正常读取到写入的数据

3、和1情况一样。errno=8, 读端fd报：Bad file descriptor。不会触发SIGPIPE， errno也不会为EPIPE

4、会触发SIGPIPE。

如果程序不处理SIGPIPE或者按照默认方式处理SIGPIPE，则程序会退出。

如果忽略SIGPIPE（ 使用signal(SIGPIPE, SIG_IGN); ），则程序不会因为系统触发SIGPIPE而退出，会继续执行完。

在向管道写端写入数据时，errno=8， 为EPIPE， 报：Broken pipe

1、程序中忽略 SIGPIPE信号。

2、向管道写端写入数据时，可以检测errno是否为EPIPE，如果是，可以关闭管道写端fd。

/* * pipe_op.c * *  Created on: Jun 24, 2014 *      Author: lingyun */#include "pipe_op.h"#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/socket.h>#include <sys/types.h>#include <assert.h>#include <stdio.h>#include <errno.h>#include <fcntl.h>#include <bits/signum.h>#include <signal.h>#define BUFFER_SIZE 1024voidpipe_create(int pipefd[2]) {    int ret;    ret = socketpair(PF_UNIX, SOCK_STREAM, 0, pipefd);    assert(ret != -1);}voidpipe_close(int pipefd) {    if (pipefd > 0) {        close(pipefd);    }}voidpipe_func_test() {    //忽略SIGPIP信号    signal(SIGPIPE, SIG_IGN);    //按照默认处理方式处理SIGPIP信号    //signal(SIGPIPE, SIG_DFL);    int pipefd[2];    pipe_create(pipefd);    int pipe_read_fd = pipefd[0];    int pipe_write_fd = pipefd[1];    printf("pipe read end: %d\n", pipe_read_fd);    printf("pipe write end: %d\n", pipe_write_fd);    //write msg to write_pipe, and read from read_pipe    char buf[BUFFER_SIZE];    memset(buf, '
/** pipe_op.c**  Created on: Jun 24, 2014*      Author: lingyun*/#include "pipe_op.h"#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/socket.h>#include <sys/types.h>#include <assert.h>#include <stdio.h>#include <errno.h>#include <fcntl.h>#include <bits/signum.h>#include <signal.h>#define BUFFER_SIZE 1024voidpipe_create(int pipefd[2]) {int ret;ret = socketpair(PF_UNIX, SOCK_STREAM, 0, pipefd);assert(ret != -1);}voidpipe_close(int pipefd) {if (pipefd > 0) {close(pipefd);}}voidpipe_func_test() {//忽略SIGPIP信号signal(SIGPIPE, SIG_IGN);//按照默认处理方式处理SIGPIP信号//signal(SIGPIPE, SIG_DFL);int pipefd[2];pipe_create(pipefd);int pipe_read_fd = pipefd[0];int pipe_write_fd = pipefd[1];printf("pipe read end: %d\n", pipe_read_fd);printf("pipe write end: %d\n", pipe_write_fd);//write msg to write_pipe, and read from read_pipechar buf[BUFFER_SIZE];memset(buf, '\0', BUFFER_SIZE);const char* message = "hello, i'm lingyun";int message_len = strlen(message);strncpy(buf, message, message_len);printf("buf message: %s\n", buf);//1. 向管道写端写数据前, 关闭管道写端fd//pipe_close(pipe_write_fd);//4. 向管道写端写数据前, 关闭管道读端fdpipe_close(pipe_read_fd);ssize_t writed = 0;writed = write(pipe_write_fd, buf, message_len);int save_errno;if (writed == -1) {save_errno = errno;if (errno == EPIPE) {printf("pipe_write_fd is closed, write to this fd has EPIPE error\n");}perror("write");goto failed;}printf("want write message len: %d\n", message_len);printf("writed %d char\n", writed);memset(buf, '\0', BUFFER_SIZE);ssize_t readed = 0;//2. 向管道写端写完数据后, 关闭管道写端fd//pipe_close(pipe_write_fd);//3. 向管道写端写完数据后, 从管道读端读取数据前, 关闭管道读端fd//pipe_close(pipe_read_fd);readed = read(pipe_read_fd, buf, writed);if (readed == -1) {save_errno = errno;if (errno == EPIPE) {printf("pipe_write_fd is closed, read from pipe_read_fd has EPIPE error\n");}perror("read");goto failed;}printf("want read message len: %d\n", writed);printf("readed %d char\n", readed);printf("after read, buf message: %s\n", buf);failed:if(pipe_read_fd != -1) {pipe_close(pipe_read_fd);}if(pipe_write_fd != -1) {pipe_close(pipe_write_fd);}}int main() {pipe_func_test();return 0;}
', BUFFER_SIZE);    const char* message = "hello, i'm lingyun";    int message_len = strlen(message);    strncpy(buf, message, message_len);    printf("buf message: %s\n", buf);    //1. 向管道写端写数据前, 关闭管道写端fd    //pipe_close(pipe_write_fd);    //4. 向管道写端写数据前, 关闭管道读端fd    pipe_close(pipe_read_fd);    ssize_t writed = 0;    writed = write(pipe_write_fd, buf, message_len);    int save_errno;    if (writed == -1) {        save_errno = errno;        if (errno == EPIPE) {            printf("pipe_write_fd is closed, write to this fd has EPIPE error\n");        }        perror("write");        goto failed;    }    printf("want write message len: %d\n", message_len);    printf("writed %d char\n", writed);    memset(buf, '
/** pipe_op.c**  Created on: Jun 24, 2014*      Author: lingyun*/#include "pipe_op.h"#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/socket.h>#include <sys/types.h>#include <assert.h>#include <stdio.h>#include <errno.h>#include <fcntl.h>#include <bits/signum.h>#include <signal.h>#define BUFFER_SIZE 1024voidpipe_create(int pipefd[2]) {int ret;ret = socketpair(PF_UNIX, SOCK_STREAM, 0, pipefd);assert(ret != -1);}voidpipe_close(int pipefd) {if (pipefd > 0) {close(pipefd);}}voidpipe_func_test() {//忽略SIGPIP信号signal(SIGPIPE, SIG_IGN);//按照默认处理方式处理SIGPIP信号//signal(SIGPIPE, SIG_DFL);int pipefd[2];pipe_create(pipefd);int pipe_read_fd = pipefd[0];int pipe_write_fd = pipefd[1];printf("pipe read end: %d\n", pipe_read_fd);printf("pipe write end: %d\n", pipe_write_fd);//write msg to write_pipe, and read from read_pipechar buf[BUFFER_SIZE];memset(buf, '\0', BUFFER_SIZE);const char* message = "hello, i'm lingyun";int message_len = strlen(message);strncpy(buf, message, message_len);printf("buf message: %s\n", buf);//1. 向管道写端写数据前, 关闭管道写端fd//pipe_close(pipe_write_fd);//4. 向管道写端写数据前, 关闭管道读端fdpipe_close(pipe_read_fd);ssize_t writed = 0;writed = write(pipe_write_fd, buf, message_len);int save_errno;if (writed == -1) {save_errno = errno;if (errno == EPIPE) {printf("pipe_write_fd is closed, write to this fd has EPIPE error\n");}perror("write");goto failed;}printf("want write message len: %d\n", message_len);printf("writed %d char\n", writed);memset(buf, '\0', BUFFER_SIZE);ssize_t readed = 0;//2. 向管道写端写完数据后, 关闭管道写端fd//pipe_close(pipe_write_fd);//3. 向管道写端写完数据后, 从管道读端读取数据前, 关闭管道读端fd//pipe_close(pipe_read_fd);readed = read(pipe_read_fd, buf, writed);if (readed == -1) {save_errno = errno;if (errno == EPIPE) {printf("pipe_write_fd is closed, read from pipe_read_fd has EPIPE error\n");}perror("read");goto failed;}printf("want read message len: %d\n", writed);printf("readed %d char\n", readed);printf("after read, buf message: %s\n", buf);failed:if(pipe_read_fd != -1) {pipe_close(pipe_read_fd);}if(pipe_write_fd != -1) {pipe_close(pipe_write_fd);}}int main() {pipe_func_test();return 0;}
', BUFFER_SIZE);    ssize_t readed = 0;    //2. 向管道写端写完数据后, 关闭管道写端fd    //pipe_close(pipe_write_fd);    //3. 向管道写端写完数据后, 从管道读端读取数据前, 关闭管道读端fd    //pipe_close(pipe_read_fd);    readed = read(pipe_read_fd, buf, writed);    if (readed == -1) {        save_errno = errno;        if (errno == EPIPE) {            printf("pipe_write_fd is closed, read from pipe_read_fd has EPIPE error\n");        }        perror("read");        goto failed;    }    printf("want read message len: %d\n", writed);    printf("readed %d char\n", readed);    printf("after read, buf message: %s\n", buf);failed:    if(pipe_read_fd != -1) {        pipe_close(pipe_read_fd);    }    if(pipe_write_fd != -1) {        pipe_close(pipe_write_fd);    }}int main() {    pipe_func_test();    return 0;}