Login or Register to Ask a Question and Join Our Community

Sponsored Content
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
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Bash multiple output redirection

Hello all. Is there a way to redirect output to more than one file at a time? I have a method1() that writes to a logfile. In the method cksums are done on files by doing a "for i in `ls`; do cksum $i > $LOGFILE done " In the logfile I want to show the cksums under each directory like... (2 Replies)
Discussion started by: yoi2hot4ya
2 Replies

2. Shell Programming and Scripting

question on redirection (<<)

I came across the following problem, where file contents are overwritten using redirection. Can somebody please explain what cat << BAR seems to be doing and say why this is a problem? Explain the contents and relation between the two filenames used before the cat command. thanks /tmp# echo... (2 Replies)
Discussion started by: newkidintown
2 Replies

3. Shell Programming and Scripting

input redirection question

Hi, in my script I need to execute the following command: query $id 456 432 but it waits for a RETURN character from keyboard and therefore, it fails. I tried something like: query $id 456 432 << '\n' but, i'ts clear it is not correct. Is there any way to do this? Thxs. (0 Replies)
Discussion started by: luistid
0 Replies

4. Shell Programming and Scripting

File redirection question

Hi all, I am working with the Grinder tool (unrelated to my question) to redirect the output of a program to a file as follows: java -cp $CLASSPATH net.grinder.TCPProxy > grinder.txt This is a proxy server which pipes output to a file. When I do something on my proxy, more and more goes to... (1 Reply)
Discussion started by: Annorax
1 Replies

5. Shell Programming and Scripting

BASH Problem / Question regarding redirection

Hi all, Maybe someone is able to help: Need to redirect the output of a command in realtime to a second command. Command-A executes a remote shell to another host, and outputs its results. Command-B displays a "dialog" with the outputs of Command-A. Command-A Output: Updating FileA... (2 Replies)
Discussion started by: mharald
2 Replies

6. Shell Programming and Scripting

Redirection Question

I just wondered if I'm understanding this command line correctly cat 2>save1 0<memo | sort 2>save2 1>letter This means that stdin will read from memo and if there is an error then stderr will write to save1. Am I correct in saying that the sort command will sort the memo file and write... (2 Replies)
Discussion started by: snag49ers
2 Replies

7. Shell Programming and Scripting

Question about IO redirection

for shell operators like <, >, <<, and >> do the LHS always have to be a process or device and the RHS a file or device? Is it possible for the RHS to be a process? (1 Reply)
Discussion started by: stevenswj
1 Replies

8. Shell Programming and Scripting

Redirection question

I want to redirect stderr and have the following peice of code $ cat t1.ksh #!/bin/ksh func2() { diff /tmp/jdlkwjdlkejew /tmp/djlkwejdlewdjew >$OUTPUT_FILE 2>>$ERR_FILE } func1() { let counter=0 while do print -u2 "Error: In main function" func2 let... (1 Reply)
Discussion started by: BeefStu
1 Replies

9. Shell Programming and Scripting

Error redirection question

Hi gurus, I have a question, need some of your inputs... I have a command like this : export LINE_COUNT=`wc -l test.dat | awk '{print $1}'` echo $LINE_COUNT --- > gives me 2 which is fine as the file has 2 lines. This works fine if the file test.dat is present but in case... (3 Replies)
Discussion started by: calredd
3 Replies

10. Shell Programming and Scripting

Input redirection within bash script

Hi, when I try to redirect input and the command is described as a string within an array redirection does not work. why? #!/bin/bash dir=("tail < ./hello.txt") tail < ./hello.txt #works ${dir} #does not work (2 Replies)
Discussion started by: heinzel
2 Replies

LEARN ABOUT CENTOS

bashbug-64

BASHBUG(1)						      General Commands Manual							BASHBUG(1)

NAME

       bashbug - report a bug in bash

SYNOPSIS

       bashbug [--version] [--help] [email-address]

DESCRIPTION

       bashbug	is  a shell script to help the user compose and mail bug reports concerning bash in a standard format.	bashbug invokes the editor
       specified by the environment variable EDITOR on a temporary copy of the bug report format outline. The user must fill  in  the  appropriate
       fields  and  exit  the  editor.	 bashbug  then	mails the completed report to bug-bash@gnu.org, or email-address.  If the report cannot be
       mailed, it is saved in the file dead.bashbug in the invoking user's home directory.

       The bug report format outline consists of several sections.  The first section provides information about the  machine,	operating  system,
       the  bash  version, and the compilation environment.  The second section should be filled in with a description of the bug.  The third sec-
       tion should be a description of how to reproduce the bug.  The optional fourth section is for a proposed fix.  Fixes are encouraged.

ENVIRONMENT

       bashbug will utilize the following environment variables if they exist:

       EDITOR Specifies the preferred editor. If EDITOR is not set, bashbug defaults to emacs.

       HOME   Directory in which the failed bug report is saved if the mail fails.

       TMPDIR Directory in which to create temporary files and directories.

SEE ALSO

       bash(1)

AUTHORS

       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet@po.cwru.edu

GNU Bash-4.0							   1998 July 30 							BASHBUG(1)
All times are GMT -4. The time now is 03:47 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy