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Title:
What does ${_[0]} mean in bash?
ID:
/2020/07/05/What-does-____0__-mean-in-bash_
Created:
July 5, 2020
Edited: July 5, 2020
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April 28, 2025
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As others have mentioned ${_[0]} is extra typing for ${_} which in turn can be abbreviated into $_ as it is most commonly used.
As mentioned previously it is a variable that contains the last parameter of the last command used. A practical application is like this:
$ ll /etc/lsb-release
-rw-r--r-- 1 root root 105 Feb 20 2019 /etc/lsb-release
$ cat $_
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.6 LTS"
In the first command the last parameter is /etc/lsb-release. In the second command the parameter is $_, which repeats /etc/lsb-release so you don’t have to retype it.