Bash substitute variable in command

Question

myDir = 'apple'

If I have the above variable, what functionality can I use to use it within a command? (I'm guessing it's some type of substitution - so I'd like to know what it's called if so)

How could I use the above variable to do an ls /home/applefruit, as obviously ls /home/$myDirfruit does not work.

heemayl · Accepted Answer · 2016-06-25 20:07:07Z

2

First of all, your variable declaration is not right. There must be no spaces around = in declaration:

myDir='apple'

Now, ls /home/$myDirfruit did not work because myDirfruit is being treated as the variable name instead of just myDir. You need to use {} to enclose the variable name when the name is being followed by valid variable name constituent character:

ls /home/${myDir}fruit

would be expanded to:

ls /home/applefruit

Also if you have spaces in variable name e.g. myDir='foo bar', use quotes around variable:

ls /home/"${myDir}"fruit

edited Jun 25, 2016 at 20:07

answered Jun 25, 2016 at 20:01

heemayl

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1 Comment

chepner Over a year ago

Just for completeness, the quotes are sufficient when quoting $myDir alone to drop the braces. ls /home/"$myDir"fruit. In general, the braces are the canonical way to expand a parameter, but may be dropped when the name of the parameter remains unambiguous.

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