Linux pipe function

1. Function description

pipe (create pipeline):
1) Header file #includef55648144b4a1c5cce7ad2f6519be0f3
2) Define function: int pipe(int filedes[2]);
3) Function description: pipe() The pipeline will be established and the file descriptor will be returned from the parameter filedes array. [Filedes [0] is the read -end of the pipe
FileDes [1] is the writing end of the pipeline.
4) Return value: If successful, return zero, otherwise return -1, and the error reason is stored in errno.

Error code:

The EMFILE process has exhausted the maximum number of file descriptors
The ENFILE system has no file descriptors available.参 EFAULT parameter FileDes array address illegal.


2. Example

#include <unistd.h>  
#include <stdio.h>  
  
int main( void )  
{  
    int filedes[2];  
    char buf[80];  
    pid_t pid;  
      
    pipe( filedes );  
    pid=fork();          
    if (pid > 0)  
    {  
        printf( "This is in the father process,here write a string to the pipe.\n" );  
        char s[] = "Hello world , this is write by pipe.\n";  
        write( filedes[1], s, sizeof(s) );  
        close( filedes[0] );  
        close( filedes[1] );  
    }  
    else if(pid == 0)  
    {  
        printf( "This is in the child process,here read a string from the pipe.\n" );  
        read( filedes[0], buf, sizeof(buf) );  
        printf( "%s\n", buf );  
        close( filedes[0] );  
        close( filedes[1] );  
    }  
      
    waitpid( pid, NULL, 0 );  
      
    return 0;  
}

Run result:

[root@localhost src]# gcc pipe.c

[root@localhost src]# ./a.out
This is in the child process, here read a string from the pipe.
This is in the father process,here write a string to the pipe.
Hello world, this is write by pipe.


When the data in the pipe is read, the pipe is empty. A subsequent read() call will by default block, waiting for some data to be written.非 If you need to be set to non -blocking, you can make the following settings:

FCNTL (FileDes [0], F_SETFL, O_NONBLOCK);

FCNTL (FileDes [1], F_SETFL, O_NONBLOCK);