pipe(2) 							System Calls Manual							   pipe(2)

NAME

       pipe -  Creates an interprocess channel

SYNOPSIS

       #include <unistd.h>

       int pipe (      int filedes[2] );

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       pipe(): XSH5.0

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies the address of an array of two integers into which the new file descriptors are placed.

DESCRIPTION

       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 on file descriptor filedes[0] accesses
       the data written to filedes[1] on a first-in, first-out (FIFO) basis.

       System V Compatibility

       The pipe() function creates an interprocess channel called a pipe and returns two file descriptors, filedes[0] and filedes[1].	Both  file
       descriptors  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.

       Under both behaviors, 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.

NOTES

       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 is different from previous  releases,  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.

       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.

RETURN VALUES

       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.

ERRORS

       If the pipe() function fails, errno may be set to one of the following values: The filedes parameter is an invalid address.  A read() or  a
       write()	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 descrip-
	      tors.

RELATED INFORMATION

       Commands: sh(1)

       Functions: fcntl(2), getmsg(2), poll(2), putmsg(2), read(2), select(2), write(2), getdtablesize(2)

       Standards: standards(5) delim off

																	   pipe(2)