pipe - create an interprocess communication channel
int pipe(int fildes)
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 up to PIPE_MAX bytes of
data are buffered before the writing process is suspended. A read using
the descriptor fildes will pick up the data.
PIPE_MAX equals 7168 under Minix, but note that most systems use 4096.
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
Read calls on an empty pipe (no buffered data) with only one end (all
write file descriptors closed) returns an end-of-file.
The signal SIGPIPE is generated if a write on a pipe with only one end is
The function value zero is returned if the pipe was created; -1 if an
The pipe call will fail if:
[EMFILE] Too many descriptors are active.
[ENFILE] The system file table is full.
[ENOSPC] The pipe file system (usually the root file system) has no
[EFAULT] The fildes buffer is in an invalid area of the process's
sh(1), read(2), write(2), fork(2).
Writes may return ENOSPC errors if no pipe data can be buffered, because
the pipe file system is full.
Should more than PIPE_MAX bytes be necessary in any pipe among a loop of
processes, deadlock will occur.