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pipe - create descriptor pair for interprocess communication



      pipe - create descriptor pair for interprocess communication


      Standard C Library (libc, -lc)


      #include <unistd.h>
      pipe(int *fildes);


      The pipe() system call creates a pipe, which is an object allowing bidi‐
      rectional data flow, and allocates a pair of file descriptors.
      By convention, the first descriptor is normally used as the read end of
      the pipe, and the second is normally 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 that has had an end 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
      The bidirectional nature of this implementation of pipes is not portable
      to older systems, so it is recommended to use the convention for using
      the endpoints in the traditional manner when using a pipe in one direc‐
      The pipe() function returns the value 0 if successful; otherwise the
      value -1 is returned and the global variable errno is set to indicate the


      The pipe() system call will fail if:
      [EMFILE]           Too many descriptors are active.
      [ENFILE]           The system file table is full.
      [ENOMEM]           Not enough kernel memory to establish a pipe.
      [EFAULT]           The fildes buffer is in an invalid area of the pro‐
                         cess’s address space.
      sh(1), fork(2), read(2), socketpair(2), write(2)


      The pipe() function appeared in Version 3 AT&T UNIX.
      Bidirectional pipes were first used on AT&T System V.4 UNIX.


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.