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
RBASH(1)						      General Commands Manual							  RBASH(1)

NAME
rbash - restricted bash, see bash(1) RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow- ing are disallowed or not performed: o changing directories with cd o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV o specifying command names containing / o specifying a filename containing a / as an argument to the . builtin command o specifying a filename containing a slash as an argument to the -p option to the hash builtin command o importing function definitions from the shell environment at startup o parsing the value of SHELLOPTS from the shell environment at startup o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators o using the exec builtin command to replace the shell with another command o adding or deleting builtin commands with the -f and -d options to the enable builtin command o using the enable builtin command to enable disabled shell builtins o specifying the -p option to the command builtin command o turning off restricted mode with set +r or set +o restricted. These restrictions are enforced after any startup files are read. When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script. SEE ALSO
bash(1) GNU Bash-4.0 2004 Apr 20 RBASH(1)
All times are GMT -4. The time now is 12:28 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy