NAME
pipe —
create descriptor pair for interprocess
communication
SYNOPSIS
#include
<unistd.h>
int
pipe(int fildes[2]);
DESCRIPTION
The
pipe()
function creates a pipe (an object that allows
unidirectional data flow) and allocates a pair of file descriptors. The
first descriptor connects to the
read end
of the pipe; the second connects to the
write
end.
Data written to fildes[1] appears on (i.e., can be read from) fildes[0]. This allows the output of one program to be sent to another program: the source's standard output is set up to be the write end of the pipe; the sink's standard input is set up to be the read end of the pipe. The pipe itself persists until all of its associated descriptors are closed.
A pipe whose read or write end has been closed is
considered
widowed. Writing
on such a pipe causes the writing process to receive a
SIGPIPE signal. Widowing a pipe is the only way to
deliver end-of-file to a reader: after the reader consumes any buffered
data, reading a widowed pipe returns a zero count.
The generation of the SIGPIPE signal can
be suppressed using the F_SETNOSIGPIPE fcntl
command.
RETURN VALUES
On successful creation of the pipe, zero is returned. Otherwise, a value of -1 is returned and the variable errno set to indicate the error.
ERRORS
The pipe() call will fail if:
- [
EFAULT] - The fildes buffer is in an invalid area of the process's address space.
- [
EMFILE] - Too many descriptors are active.
- [
ENFILE] - The system file table is full.
SEE ALSO
HISTORY
A pipe() function call appeared in
Version 6 AT&T UNIX.