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named pipe                  Definition                 named pipe




A  _n_a_m_e_d  _p_i_p_e  is  a  special  file  created  with  the  command
/eettcc/mmkknnoodd. Unlike the block- and character-special files created
by mmkknnoodd, a named pipe is not a device.

A named pipe acts like a conventional pipe set up between related
processes.  It differs in that it  has a visible name that can be
seen  in  a  file  system.   It  also  differs  in  that  it  has
permissions (since it's a file and has a name) associated with it
just  like  any other  file.   This  allows a  named  pipe to  be
accessed by processes that are _n_o_t related to each other, and can
even  be  used  for  processes  that  are running  on  behalf  of
difference users.

The following  illustrates how one process can  write data into a
named pipe and an unrelated process can read from it:


     /etc/mknod my_pipe p     # create the named pipe
     chmod 644 my_pipe
     ls -lR / > my_pipe &     # pump data into pipe in background
     mail fred < my_pipe      # read from the pipe and process


This script  creates a named  pipe called mmyy_ppiippee  and makes sure
that it is  readable; it then pumps a mass  of data into the pipe
(in the  background), and then  has a process read  data from the
named pipe  and perform some  action on them (in  this case, mail
the data  to use ffrreedd).  In this example,  the mmaaiill process could
be  running from  some other  login  and could  either be  in the
foreground or background.

***** See Also *****

ddeeffiinniittiioonnss, mmkknnoodd, ppiippee






















COHERENT Lexicon                                           Page 1

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