pipe - Create an interprocess channel
#include <unistd.h>
int pipe(
int filedes[2] );
Interfaces documented on this reference page conform to
industry standards as follows:
pipe(): XSH4.0, XSH4.2, XSH5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies the address of an array of two integers into
which the new file descriptors are placed.
The pipe() function creates a unidirectional interprocess
channel called a pipe, and returns two file descriptors,
filedes[0] and filedes[1]. The file descriptor specified
by the filedes[0] parameter is opened for reading and the
file descriptor specified by the filedes[1] parameter is
opened for writing. Their integer values will be the two
lowest available at the time of the call to the pipe()
function.
A process has the pipe open for reading if it has a file
descriptor open that refers to the read end, filedes[0]. A
process has the pipe open for writing if it has a file
descriptor open that refers to the write end, filedes[1].
A read operation on file descriptor filedes[0] accesses
the data written to filedes[1] on a first-in, first-out
(FIFO) basis.
Note
In the System V compatiblity environment, filedes[0] and
filedes[1] are STREAMS based and are bidirectional. Data
written on filedes[0] appears on filedes[1] and vice
versa. Data is read in a first-in, first-out (FIFO) basis.
The O_NONBLOCK and the FD_CLOEXC flags are set clear on
both file descriptors. (The fcntl() function can be used
to set the O_NONBLOCK flag.)
Upon successful completion, the pipe() function marks the
st_atime, st_ctime and st_mtime fields of the pipe for
update.
[Tru64 UNIX] When a read() or write() system call on a
pipe is interrupted by a signal and no bytes have been
transferred through the pipe, the read() or write() system
call returns a -1 and errno is set to [EINTR]. This behavior
differs from behavior in early releases of the operating
system, when both system calls either restarted the
transfer or caused errno to be set to [EINTR], depending
on the setting of the SA_RESTART flag for the interrupting
signal.
[Tru64 UNIX] As a result of this change, applications
must now either handle the [EINTR] return or block any
expected signals for the duration of the read or write
operation.
[Tru64 UNIX] When compiled in the X/Open UNIX environment,
calls to the pipe() function are internally renamed
by prepending _E to the function name. When you are debugging
a module that includes the pipe() function and for
which _XOPEN_SOURCE_EXTENDED has been defined, use _Epipe
to refer to the pipe() call. See standards(5) for further
information.
Upon successful completion, a value of 0 (zero) is
returned. If the pipe() function fails, a value of -1 is
returned and errno is set to indicate the error.
If the pipe() function fails, errno may be set to one of
the following values: [Tru64 UNIX] The filedes parameter
is an invalid address. [Tru64 UNIX] A read() or a
write() call on a pipe is interrupted by a signal and no
bytes have been transferred through the pipe. More than
OPEN_MAX-2 file descriptors are already opened by this
process.
[Tru64 UNIX] More than getdtablesize(2) file
descriptors are already opened by this process.
The system file table is full, or the device containing
pipes has no free i-nodes. [Tru64
UNIX] The system was unable to allocate kernel
memory for more file descriptors.
Commands: sh(1)
Functions: fcntl(2), getmsg(2), getdtablesize(2), poll(2),
putmsg(2), read(2), select(2), write(2)
Standards: standards(5)
pipe(2)
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