#include <unistd.h>int pipe(int fildes);
The pipe() function creates an I/O mechanism called a pipe and returns two file descriptors, fildes and fildes. The files associated with fildes and fildes are streams and are both opened for reading and writing. The O_NDELAY and O_NONBLOCK flags are cleared.
A read from fildes accesses the data written to fildes on a first-in-first-out (FIFO) basis and a read from fildes accesses the data written to fildes also on a FIFO basis.
The FD_CLOEXEC flag will be clear on both file descriptors.
Upon successful completion pipe() marks for update the st_atime, st_ctime, and st_mtime fields of the pipe.
Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.
The pipe() function will fail if:
There are OPEN_MAX-1 or more file descriptors currently open for this process.
A file table entry could not be allocated.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
Since a pipe is bi-directional, there are two separate flows of data. Therefore, the size (st_size) returned by a call to fstat(2) with argument fildes or fildes is the number of bytes available for reading from fildes or fildes respectively. Previously, the size (st_size) returned by a call to fstat() with argument fildes (the write-end) was the number of bytes available for reading from fildes (the read-end).