Bash - Concatenating Variable on to Path

Question

Currently, I have a bash script that will untar a file in my root directory:

#!/bin/bash
tar xvf ~/some-file.tar

This works without problems. Now, I would like to change this so I can specify the path to the file in a pre-defined variable like such:

#!/bin/bash
p="~"
tar xvf $p/some-file.tar

This gives me the following error message:

tar: ~/some-file.tar: Cannot open: No such file or directory
tar: Error is not recoverable: exiting now

The path to the file seems to be correct, however, are there some hidden characters causing this to fail? What is the proper way to concatenate a variable and a path without storing both in string variables (if there is one)?

This was simply an example, the reason I would like to store the path in a variable is because it may change based on how the script is run — kshah
– kshah, Commented Jul 14, 2015 at 16:45
Always test the simplest thing ;) stackoverflow.com/help/mcve — Karoly Horvath
– Karoly Horvath, Commented Jul 14, 2015 at 17:42

user000001 · Accepted Answer · 2015-07-14 16:54:06Z

6

Tilde expansion doesn't work when inside a variable. You can use the $HOME variable instead:

#!/bin/bash
p=$HOME
tar xvf "$p/some_file.tar"

edited Jul 14, 2015 at 16:54

answered Jul 14, 2015 at 16:45

user000001

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5 Comments

kshah Over a year ago

Ah, I see. I did not realize that the error was due to the tilde. Thanks!

kshah Over a year ago

One question however: I plan to take the path as a command line option in my script. How do I handle the ~ if the user decides to enter it?

Jason Hu Over a year ago

just a side note: ~ only works when it's the first char of the argument with no quote. for example, echo abc=~ will print literally.

user000001 Over a year ago

@kshah You don't need to handle it. It will be interpreted by the shell when the user types it in his terminal.

Jason Hu Over a year ago

@kshah it's better for you to delegate to other tool to make your life easier, like python, have a look at os.path.expanduser. too naive solution won't work, for example, tilde expansion support user name suffix: ~user1 should expand to home folder of user1.

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