Bash scripting: mkdir error

Question

I have the following script sample:

#!/bin/bash

# Aborts the script on "simple command failure" (does not cover pipes)
set -e

# Makes sure we do not run the script outside the correct directory (i.e. the backup directory)
projects_directory='~/projects' 
backup_drectory="${projects_directory}/backup/"
echo "Backup directory: ${backup_drectory}"

if [ ! -d "$projects_directory" ]; then 
    mkdir "$projects_directory"
    echo "${projects_directory} created successfully" 
fi

Which fails miserably with the following output:

Backup directory: ~/projects/backup/
mkdir: cannot create directory `~/projects': No such file or directory

I do not understand why. If I enter the mkdir ~/projects command manually in a Terminal, the directory gets created. Any suggestion is most welcome.

Try to replace the ~ with your absolute home directory (/home/username/). Which user executes your backup script (are you using a cron job?) — Gregor
– Gregor, Commented Sep 15, 2012 at 12:32
I am planning to use cron, yes. So far I am testing it manually via Terminal. Your solution works. Could you explain to me why ? Is ther any workaround so I do not have to hardcode the user path into the script ? — Alexandre Bourlier
– Alexandre Bourlier, Commented Sep 15, 2012 at 12:34
Shell quoting is your enemy. You can read about how the shell handles single versus double quotes here: mywiki.wooledge.org/Quotes. — Telemachus
– Telemachus, Commented Sep 15, 2012 at 12:35
the answer given by lanzz is correct. Make sure to start the script by the correct user (using crontab -e from the users shell) — Gregor
– Gregor, Commented Sep 15, 2012 at 12:35

lanzz · Accepted Answer · 2012-09-15 12:34:34Z

7

Remove the single quotes:

projects_directory=~/projects

The quoting prevents the shell from expanding the ~ character.

answered Sep 15, 2012 at 12:34

lanzz

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3 Comments

Alexandre Bourlier Over a year ago

Thanks ! Beginner's mistake ;)

johnsyweb Over a year ago

+1. I also recommend using mkdir -p (make parent directories as needed).

Alexandre Bourlier Over a year ago

Thanks x2! So I do not need to check for ~/projects existence, I can directly issue mkdir -p ~/projects/backup. You made my day sir !

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