4.3BSD-UWisc/man/cat2/pipe.2

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PIPE(2)             UNIX Programmer's Manual              PIPE(2)



NAME
     pipe - create an interprocess communication channel

SYNOPSIS
     pipe(fildes)
     int fildes[2];

DESCRIPTION
     The _p_i_p_e system call creates an I/O mechanism called a pipe.
     The file descriptors returned can be used in read and write
     operations.  When the pipe is written using the descriptor
     _f_i_l_d_e_s[1] up to 4096 bytes of data are buffered before the
     writing process is suspended.  A read using the descriptor
     _f_i_l_d_e_s[0] will pick up the data.

     It is assumed that after the pipe has been set up, two (or
     more) cooperating processes (created by subsequent _f_o_r_k
     calls) will pass data through the pipe with _r_e_a_d and _w_r_i_t_e
     calls.

     The shell has a syntax to set up a linear array of processes
     connected by pipes.

     Read calls on an empty pipe (no buffered data) with only one
     end (all write file descriptors closed) returns an end-of-
     file.

     Pipes are really a special case of the _s_o_c_k_e_t_p_a_i_r(2) call
     and, in fact, are implemented as such in the system.

     A signal is generated if a write on a pipe with only one end
     is attempted.

RETURN VALUE
     The function value zero is returned if the pipe was created;
     -1 if an error occurred.

ERRORS
     The _p_i_p_e call will fail if:

     [EMFILE]       Too many descriptors are active.

     [ENFILE]       The system file table is full.

     [EFAULT]       The _f_i_l_d_e_s buffer is in an invalid area of
                    the process's address space.

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

BUGS
     Should more than 4096 bytes be necessary in any pipe among a



Printed 12/27/86         August 26, 1985                        1






PIPE(2)             UNIX Programmer's Manual              PIPE(2)



     loop of processes, deadlock will occur.






















































Printed 12/27/86         August 26, 1985                        2