Creates an interprocess channel.
Standard C Library (libc.a)
#include <unistd.h>int pipe ( FileDescriptor)
int FileDescriptor[2];
The pipe subroutine creates an interprocess channel called a pipe and returns two file descriptors, FileDescriptor[0] and FileDescriptor[1]. FileDescriptor[0] is opened for reading and FileDescriptor[1] is opened for writing.
A read operation on the FileDescriptor[0] parameter accesses the data written to the FileDescriptor[1] parameter on a first-in, first-out (FIFO) basis.
Write requests of PIPE_BUF bytes or fewer will not be interleaved (mixed) with data from other processes doing writes on the same pipe. PIPE_BUF is a system variable described in the pathconf (pathconf or fpathconf Subroutine) subroutine. Writes of greater than PIPE_BUF bytes may have data interleaved, on arbitrary boundaries, with other writes.
If O_NONBLOCK or O_NDELAY are set, writes requests of PIPE_BUF bytes or fewer will either succeed completely or fail and return -1 with the errno global variable set to EAGAIN. A write request for more than PIPE_BUF bytes will either transfer what it can and return the number of bytes actually written, or transfer no data and return -1 with the errno global variable set to EAGAIN.
| Item | Description |
|---|---|
| FileDescriptor | Specifies the address of an array of two integers into which the new file descriptors are placed. |
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned, and the errno global variable is set to identify the error.
The pipe subroutine is unsuccessful if one or more the following are true:
| Item | Description |
|---|---|
| EFAULT | The FileDescriptor parameter points to a location outside of the allocated address space of the process. |
| EMFILE | The number of open of file descriptors exceeds the OPEN_MAX value. |
| ENFILE | The system file table is full, or the device containing pipes has no free i-nodes. |