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Full Discussion: I/O redirection
Top Forums Shell Programming and Scripting I/O redirection Post 302503044 by Perderabo on Wednesday 9th of March 2011 01:58:41 PM
Old 03-09-2011
Quote:
Originally Posted by alister
For grep to beget ls would require more than a shell rewrite, it would require a grep one too.
Not really true. I actually said that grep was the child and ls the parent. You made a slight goof and reversed my comments. But an experiment shows that the reversed statement you attributed to me is true. So I hereby adopt it as what I meant to say. Smilie
Code:
$ /bin/sleep 60 | grep bad &
[1]     32429
$ ps -f
UID        PID  PPID  C STIME TTY          TIME CMD
xxxxx     3417  3416  0 Mar08 pts/1    00:00:00 -ksh
xxxxx    11703  3417  0 Mar08 pts/1    00:00:00 ksh
xxxxx    32424 11703  0 13:42 pts/1    00:00:00 ksh
xxxxx    32429 32424  0 13:43 pts/1    00:00:00 grep bad
xxxxx    32430 32429  0 13:43 pts/1    00:00:00 /bin/sleep 60
xxxxx    32431 32424  0 13:43 pts/1    00:00:00 ps -f
$

The grep process wound up as parent and the sleep process wound up as child. I would not want to bet that it always works that way. And no I don't have a special grep process that knew to establish the child.

32424 forked to create 32429 but both processes are still ksh because neither has exec'ed yet. 32429 then forked again to create a child 32430. At this point the whole pipeline exists and both processes exec'ed their respective programs.
 

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LEARN ABOUT V7

pts_sleep

PTS_SLEEP(1)						       AFS Command Reference						      PTS_SLEEP(1)

NAME

       pts_sleep - Pauses for a few seconds

SYNOPSIS

       pts sleep [-delay] <# of seconds>
	  [-cell] <cell name> [-noauth] [-localauth] [-force]

       pts sl [-d] <# of seconds> [-c] <cell name>
	  [-n] [-l] [-f]

DESCRIPTION

       The pts sleep pauses for a specified number of seconds. The command can be run from the command line or interactively, although from the
       command line it's essentially equivalent to the sleep command. It is intended for use in interactive mode to pause for a few seconds
       between batch commands to allow the Protection Server to catch up.

CAUTIONS

       Prior to OpenAFS 1.4.5 and OpenAFS 1.5.23, the pts sleep command was only available on Unix or Linux and when OpenAFS was compiled with the
       supergroups option (disabled by default).  As of OpenAFS 1.4.5 and 1.5.23, it is always available.

OPTIONS

       Although they have no effect, pts sleep takes the following standard pts options:

       -cell <cell name>
	   Names the cell in which to run the command. For more details, see pts(1).

       -force
	   Enables the command to continue executing as far as possible when errors or other problems occur, rather than halting execution at the
	   first error.

       -help
	   Prints the online help for this command. All other valid options are ignored.

       -localauth
	   Constructs a server ticket using a key from the local /etc/openafs/server/KeyFile file. Do not combine this flag with the -cell or
	   -noauth options. For more details, see pts(1).

       -noauth
	   Assigns the unprivileged identity anonymous to the issuer. For more details, see pts(1).

OUTPUT

       This command produces no output.

EXAMPLES

       Here is an example of a pts interactive session:

	  % pts interactive
	  pts> sleep 5
	  pts> quit
	  %

SEE ALSO

       pts(1), pts_interactive(1)

COPYRIGHT

       Copyright 2007 Jason Edgecombe <jason@rampaginggeek.com>

       This documentation is covered by the BSD License as written in the doc/LICENSE file. This man page was written by Jason Edgecombe for
       OpenAFS.

OpenAFS 							    2014-04-08							      PTS_SLEEP(1)
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