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Full Discussion: Question on bash redirection
Top Forums UNIX for Beginners Questions & Answers Question on bash redirection Post 303035996 by bakunin on Wednesday 12th of June 2019 01:36:42 AM
Old 06-12-2019
Quote:
Originally Posted by sand1234
Can I get some explanation around this bash redirection?
Code:
diff <(sort testfile.txt) <(sort testfile2.txt)

This is a so-called "process substitution", where a process (or, rather, its outout) is put into the place of a file. First, there is a diff command:

Code:
diff file1 file2

which would list the differences between these two files. Now, both "file1" and "file2" are substituted by a process:

Code:
<(sort testfile.txt)

So, the file "testfile.txt" is sorted and the result of this sorting (the output of this process) is used as input to the diff command instead of a regular file. Likewise with the second file. This mechanism is called "process substitution".

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
RavinderSingh13
 

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LEARN ABOUT DEBIAN

apsfilter-bug

APSFILTER-BUG(1)					    BSD General Commands Manual 					  APSFILTER-BUG(1)

NAME

     apsfilter-bug -- create a half-automatic bug report for apsfilter

SYNOPSIS

     apsfilter-bug

OPTIONS

     none

DESCRIPTION

     With the apsfilter-bug script you can automatically create a bug report for apsfilter(1).	A template report file is created which you can
     edit with your favourite editor ( emacs(1) by default, or whatever is entered in the environment variable EDITOR ).

     You will see a couple of lines starting with '#'; these lines will be removed before the report is sent. So if you want to use the '#' char-
     acter at the beginning of a line, just indent it with a space.

     A very important piece of the bug report is the debugging log created by aps2file(1), probably with a command like
	   aps2file -D -o /dev/null [-P...] [-Z...] [input] 2> log.txt
     Unless you don't even have a chance to create a debugging log, it is crucial for serious bug hunting.

     After you have filled in as much (useful) information as possible, you must save the file under its original name, then exit your editor.

     If you invoked apsfilter-bug by accident, or if you need some additional system information to include into the bug report, just exit your
     editor without saving the file.

NOTES

     In addition to the stuff you've edited, some more information is appended to the bug report automatically:

     apsfilter version	  7.2.6-stable
     ghostscript version  (from 'gs --version')
     system id		  (from 'uname -a')
     configure options	  --prefix=/usr --sysconfdir=/etc --mandir=/usr/share/man --with-awk=/usr/bin/awk --with-sendmail=/usr/sbin/sendmail
     shell executable	  /bin/bash
     awk executable	  /usr/bin/awk
     sendmail executable  /usr/sbin/sendmail

FILES

     /usr/bin/aps2file	script to create debugging output

SEE ALSO

     apsfilter(1), aps2file(1)

BUGS

     See apsfilter software center - http://www.apsfilter.org/ - for new versions, bugfixes and known bugs.

     Please use the new tool apsfilter-bug(1) to release bug- or problem reports. It automatically presents you a form in an editor window which
     asks you some standard questions.	If you save and quit the editor session, then this report is sent automatically via e-mail to the proper
     apsfilter mailinglist.

     If apsfilter fails to print something or prints it in a way you wouldn't expect and you want to report an apsfilter error then please save
     the debugging output of one print session using the new aps2file(1) utility by typing aps2file -D -Z options file > /dev/null 2> file.debug
     and including the debugging output in the file file.debug into the edit session of the apsfilter-bug utility, so that it is included into the
     mail to the apsfilter mailinglist.

     Please note that you need to run /bin/sh (Bourne Shell), bash or a compatible shell, so that the above mentioned output redirection works.
     Under C-shell (/bin/csh) or tcsh it would't work. If you don't know, then simply make sure you use the Bournce shell by typing /bin/sh or
     bash, then you should have no problems with redirection of stdout and stderr (> /dev/null 2> file.debug).

DOCUMENTATION

     See official apsfilter homepage
     http://www.apsfilter.org/handbook.html   Apsfilter Handbook including the Frequently Asked Questions (FAQ)

USER FORUM

     Please send questions to the official apsfilter help channel apsfilter-help@apsfilter.org.  The above section BUGS and the file
     HOWTO-BUGREPORTS tells you how to report bugs.  If you want to know how to troubleshoot your apsfilter installation, please read the manpage
     aps2file(1) and apsfilter-bug(1) as well as the Apsfilter Handbook carefully.

HISTORY

     The apsfilter-bug manpage has been written by Michael LoBin <phallobst@web.de> and first appeared in apsfilter V 7.1.0.

BSD
								   Dec 26, 2001 							       BSD
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