NAME
pipe —
create descriptor pair for interprocess
communication
SYNOPSIS
#include
<unistd.h>
int
pipe(int
*fildes);
DESCRIPTION
Thepipe()
function creates a pipe, which is an object allowing
unidirectional data flow, and allocates a pair of file descriptors. The first
descriptor connects to the
read end of
the pipe, and the second connects to the
write end,
so that 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, and the sink's standard input is set up to be
the read end of the pipe. The pipe itself persists until all 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.
Pipes are really a special case of the socketpair(2) call and, in fact, are implemented as such in the system.
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:
- [
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
HISTORY
A pipe function call appeared in Version 6
AT&T UNIX.