Linked Questions

4
votes
2answers
338 views

Command substitution declaration syntax in bash - which of these two is better practice? [duplicate]

This is part of a bash find loop, and I wondered which is more correct syntax and why? filename="$(echo "$i" | cut -c5-)"; filename=`echo "$i" | cut -c5-`; Both function for the purpose of getting ...
-2
votes
3answers
3k views

What does $( … ) mean in the shell? [duplicate]

I don't understand what does the dollar sign do. Especially in this context: for url in $(cat example.txt); do host $url;
4
votes
1answer
214 views

Different behavior of $() and `` [duplicate]

% PATH="MYPATH" % VAR="PATH" % echo $(eval echo \$$VAR) MYPATH % echo `eval echo \$$VAR` 5707VAR ^^ This is the process number. I thought those two were exactly the same, but obviously there are ...
0
votes
2answers
197 views

What's the difference of get command output using`command`and $(command) in Shell? [duplicate]

What is the difference in collect a command output in Shell script using `command` and $(command)? For example: # IP1=$(ifconfig eth0 | grep -e "inet " | cut -d: -f2 | awk '{print $1}') # IP2=`...
2
votes
1answer
224 views

What's the practical difference between `command` and $(command)? [duplicate]

Both give the output of the command, so what is the semantic difference between the two? Some reading led me to suspect is that $(command) is Bash syntax, and the back quotes are integrated into Unix ...
1
vote
0answers
64 views

What's the difference between `` and $()? [duplicate]

When you want to return a command line output, you may consider using two methods: `cat file` or $(cat file). As far as I know, they are equivalent before my eyes. Is there a difference between both? ...
0
votes
0answers
26 views

Nesting back-ticked commands [duplicate]

I have this which won't work: source_dir=`cd `dirname `readlink "$BASH_SOURCE"`` && pwd`; what does work is this tho: source_dir=$(cd $(dirname $(readlink "$BASH_SOURCE")) && pwd); ...
262
votes
15answers
124k views

Get exit status of process that's piped to another

I have two processes foo and bar, connected with a pipe: $ foo | bar bar always exits 0; I'm interested in the exit code of foo. Is there any way to get at it?
149
votes
6answers
244k views

What does ` (backquote/backtick) mean in commands?

I came across the following command: sudo chown `id -u` /somedir and I wonder: what is the meaning of the ` symbol. I noticed for instance that while the command above works well, the one below does ...
20
votes
4answers
12k views

bulk rename (or correctly display) files with special characters

I have a bunch of directories and subdirectories that contain files with special characters, like this file: robbie@phil:~$ ls test�sktest.txt test?sktest.txt Find reveals an escape sequence: ...
17
votes
6answers
2k views

Use system command instead of Bash builtin without specifying the full path

I use Bash as my interactive shell and I was wondering if there was an easy way to get Bash to run a system command instead of a shell builtin command in the case where they both share the same name. ...
8
votes
3answers
2k views

How to check if stdin is /dev/null from the shell?

On Linux, is there a way for a shell script to check if its standard input is redirected from the null device (1, 3) *, ideally without reading anything? The expected behavior would be: ./...
11
votes
4answers
27k views

How to use “cat” command on “find” command's output?

I want to redirect the output of the find command to cat command so I can print the data of the given file. So for example if the output of find is /aFile/readme then the cat should be interpreted ...
4
votes
4answers
3k views

Finding duplicate users on CentOS

I'm using the following code to find the duplicate username. However, it gives an error. #!/bin/bash cat /etc/passwd | cut -f1 -d":" | /bin/sort -n | /usr/bin/uniq -c |\ while read x; do [ -z "${...
4
votes
2answers
9k views

How do I handle special characters like a bracket in a bash script?

I am trying to get the output of some programs and assign them to variables. I am using backticks to do it, but I can switch to a different method if necessary. What I notice is that often I do not ...

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