CODEWITHSUNDEEP
bashshell
Vombat
Vombat

Reputation: 1166

Bash command value assignment

Can anyone please explain what the following bash command does?

CMD_PATH=${0%/*}

What is the value assigned to the CMD_PATH variable?

Upvotes: 2

Views: 94

Answers (3)

fedorqui
fedorqui

Reputation: 289555

It shows the first directory on the working running process. If it is in a script, it shows its name.

From What exactly does "echo $0" return:

$0 is the name of the running process. If you use it inside a shell, then it will return the name of the shell. If you use it inside a script, it will be the name of the script.

Let's explain it:

$ echo $0
/bin/bash

is the same as

$ echo ${0}
/bin/bash

Then a bash substitution is done: get text up to last slash:

$ echo ${0%/*}
/bin

This substitution can be understood with this example:

$ a="hello my name is me"
$ echo ${a% *}
hello my name is

Upvotes: 2

rr-
rr-

Reputation: 14811

It strips anything beyond last occurence of slash character from $0 variable, which is (in most cases, sometimes depending on how the script is run) the folder the script is currently executed from.

Upvotes: 4

Adam Siemion
Adam Siemion

Reputation: 16029

Returns the name of the directory from which the currently running script has been started.

To test it:

  • create directory /tmp/test:

    mkdir /tmp/test

  • create file 't.sh` with such content:

    #!/bin/bash

echo $0
echo ${0%/*}

  • give t.sh execution permission:

    chmod +x /tmp/test/t.sh

  • execute it and you will see:

    /tmp/test/s.sh
/tmp/test

Upvotes: 1

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