PIPE
Section: System Calls (2)
Updated: August 26, 1985
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NAME
pipe - create an interprocess communication channel
SYNOPSIS
pipe(fildes)
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 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.
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 ALSO
sh(1), read(2), write(2), fork(2), socketpair(2)
BUGS
Should more than 4096 bytes be necessary in any
pipe among a loop of processes, deadlock will occur.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- SEE ALSO
-
- BUGS
-
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