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:
 

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
LIBBASH(7)							  libbash Manual							LIBBASH(7)

NAME
libbash -- A bash shared libraries package. DESCRIPTION
libbash is a package that enables bash dynamic-like shared libraries. Actually its a tool for managing bash scripts whose functions you may want to load and use in scripts of your own. It contains a 'dynamic loader' for the shared libraries ( ldbash(1)), a configuration tool (ldbashconfig(8)), and some libraries. Using ldbash(1) you are able to load loadable bash libraries, such as getopts(1) and hashstash(1). A bash shared library that can be loaded using ldbash(1) must answer 4 requirments: 1. It must be installed in $LIBBASH_PREFIX/lib/bash (default is /usr/lib/bash). 2. It must contain a line that begins with '#EXPORT='. That line will contain (after the '=') a list of functions that the library exports. I.e. all the function that will be usable after loading that library will be listed in that line. 3. It must contain a line that begins with '#REQUIRE='. That line will contain (after the '=') a list of bash libraries that are required for our library. I.e. every bash library that is in use in our bash library must be listed there. 4. The library must be listed (For more information, see ldbashconfig(8)). Basic guidelines for writing library of your own: 1. Be aware, that your library will be actually sourced. So, basically, it should contain (i.e define) only functions. 2. Try to declare all variables intended for internal use as local. 3. Global variables and functions that are intended for internal use (i.e are not defined in '#EXPORT=') should begin with: __<library_name>_ For example, internal function myfoosort of hashstash library should be named as __hashstash_myfoosort This helps to avoid conflicts in global name space when using libraries that come from different vendors. 4. See html manual for full version of this guide. AUTHORS
Hai Zaar <haizaar@haizaar.com> Gil Ran <ril@ran4.net> SEE ALSO
ldbash(1), ldbashconfig(8), getopts(1), hashstash(1) colors(1) messages(1) urlcoding(1) locks(1) Linux Epoch Linux
All times are GMT -4. The time now is 11:31 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy