PIPE(2)

NAME
pipe - create descriptor pair for interprocess communication

SYNOPSIS
#include <unistd.h>

int pipe (int *fildes);

DESCRIPTION
The pipe 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 (end of file).

LIMITS
Up to 4096 bytes of data are buffered before the writing process is suspended. Should more than 4096 bytes be necessary in any pipe among a loop of processes, deadlock will occur. This is not a limitation specific to GNO but to multiprogramming in general.

NOTES
This man page refers to the Unix read(2) and write(2) operations. On the IIgs, the described behavior refer to any system calls doing I/O, including:
    GS/OS ReadGS and WriteGS
    TextTools calls
    C stdio I/O routines

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
sh(1), read(2), write(2), fork(2), socketpair(2)

HISTORY
A pipe function call appeared in Version 6 AT&T UNIX.