PIPE(2)PIPE(2)NAMEpipe - create an interprocess communication channel
SYNOPSIS
int pipe(int fildes[2])
DESCRIPTION
The pipe system call creates an I/O mechanism called a pipe. The file
descriptors returned can be used in read and write operations. When
the pipe is written using the descriptor fildes[1] up to 4096 bytes of
data (PIPE_BUF bytes for POSIX applications; see <limits.h>) are
buffered before the writing process is suspended. A read using the
descriptor fildes[0] will pick up the data.
It is assumed that after the pipe has been set up, two (or more)
cooperating processes (created by subsequent fork() calls) will pass
data through the pipe with read() and write() calls.
The shell has a syntax to set up a linear array of processes connected
by pipes.
Read calls on an empty pipe (no buffered data) with only one end (all
write file descriptors closed) returns an end-of-file.
Pipes are really a special case of the socketpair(2) call and, in fact,
are implemented as such in the system.
Upon successful completion, the pipe function will update the st_atime,
st_ctime, and st_mtime fields of the pipe.
A signal is generated if a write on a pipe with only one end is
attempted.
RETURN VALUE
The function value zero is returned if the pipe was created; -1 if an
error occurred.
ERRORS
The pipe call will fail if:
[EMFILE] Too many descriptors are active.
[ENFILE] The system file table is full.
[EFAULT] The fildes buffer is in an invalid area of the process's
address space.
SEE ALSOsh(1), read(2), write(2), fork(2), socketpair(2), stat(2) or stat(2P)BUGS
Should more than 4096 (PIPE_BUF for POSIX) bytes be necessary in any
pipe among a loop of processes, deadlock will occur.
August 1, 1992 PIPE(2)
