Bash command value assignment

Question

Can anyone please explain what the following bash command does?

CMD_PATH=${0%/*}

What is the value assigned to the CMD_PATH variable?

Also see http://stackoverflow.com/questions/59895/can-a-bash-script-tell-what-directory-its-stored-in — devnull, Jun 26 '13 at 12:07

score 4 · Answer 1 · edited Jun 26 '13 at 11:59

4

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.

edited Jun 26 '13 at 11:59

l0b0

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answered Jun 26 '13 at 11:57

rr-

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fedorqui · Accepted Answer · 2013-06-26T12:01:39.200

2

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

edited Jun 26 '13 at 12:01

answered Jun 26 '13 at 11:56

fedorqui

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Sure, did not check properly. See my updated answer, @anubhava – fedorqui Jun 26 '13 at 12:02

score 1 · Answer 3 · answered Jun 26 '13 at 11:56

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
```

Bash command value assignment

3 Answers3