truncate a string in bash with variable expansion formatting

Question

I am trying to truncate a string in bash, specifically to get into the directory of an executable linked by a symlink. For example:

[alva@brnzn ~ $] ls -algh $(which python3.4)
lrwxr-xr-x  1 admin    73B 26 May 02:49 /opt/local/bin/python3.4 -> /opt/local/Library/Frameworks/Python.framework/Versions/3.4/bin/python3.4

So i cut out the fields I don't need:

[alva@brnzn ~ $] ls -algh $(which python3.4) | cut -d" " -f 14
/opt/local/Library/Frameworks/Python.framework/Versions/3.4/bin/python3.4

I need help to cut out everything after the last /. I am interested in a solution were I can save the previous string in a var and using variable expansion to cut out the part of the string I dont need. e.g. printf '%s\n' "${path_str#*/}" (this is just an example).

Thank you!

Why can't you save the previous string in a variable? path_str=$(command) saves the output of a command in a variable. — Barmar
– Barmar, Commented Aug 27, 2015 at 9:54
Indeed I would do so, but the point of the question is not how to save a string in a variable, but how to truncate part of it. Thank you. — alva
– alva, Commented Aug 27, 2015 at 10:23
Sorry, it looked like you already knew how to use expansion operators to truncate part of it. — Barmar
– Barmar, Commented Aug 27, 2015 at 10:24

Community · Accepted Answer · 2017-05-23 12:30:19Z

3

You can use dirname to retrieve the final directory-name and than assign it to a variable, so the solution could be:

MY_VAR=$( dirname $(ls -algh $(which python3.4) | cut -d" " -f 14) )

But I prefer to use readlink to show the linked file so your code should be:

MY_VAR=$( dirname $( readlink $(which python3.4) )

Take a look to How to resolve symbolic links in a shell script to read the full history.

edited May 23, 2017 at 12:30

CommunityBot

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answered Aug 27, 2015 at 9:59

Alepac

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Comments

Jens · Accepted Answer · 2015-08-27 10:00:14Z

1

Would this be what you need?

$ x=/opt/local/Library/Frameworks/Python.framework/Versions/3.4/bin/python3.4
$ echo ${x%/*}
/opt/local/Library/Frameworks/Python.framework/Versions/3.4/bin

answered Aug 27, 2015 at 10:00

Jens

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3 Comments

alva Over a year ago

Thank you very much, this is exactly what I was looking for. May you point me to the documentation of the syntax you have used?

Barmar Over a year ago

@alva It's documented in the bash manual, in the section on parameter expansion.

Barmar Over a year ago

gnu.org/software/bash/manual/html_node/…

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