CODEWITHSUNDEEP
bashvariables
Scott
Scott

Reputation: 611

Not understanding basic Bash variables and command grouping

Adding in comments to ask specific questions as I go:

Single or double quote marks when settings strings?

echo "Starting..."

Do I need to terminate the line with a ;?

TARGET_DIR="~/Downloads"

I can't get the $TARGET_DIR to expand, tried quotes, preens with $etc, is there a canonical beginners guide to these types of issues that presents them in the proper way, not the force it to work with back tics and multiple lines?

LAST_DOWNLOADED_FILE=$(ls -t $TARGET_DIR | head -n1)
echo "Your newest file in $TARGET_DIR is: $LAST_DOWNLOADED_FILE"

When run on Mac, I get:

ls: ~/Downloads: No such file or directory
Your newest file in ~/Downloads is:

Trying as a one liner:

me@compy $FOO="~/Downloads"; echo $(FOO); ls -t $FOO | head -n1
-bash: FOO: command not found

Upvotes: 2

Views: 110

Answers (2)

jaypal singh
jaypal singh

Reputation: 77095

~ sign inside quotes is considered a literal by shell. You need to either keep it outside of quotes as anubhava suggested in his answer or use eval to interpolate it.

$ TARGET_DIR="~/tmp"
$ echo $TARGET_DIR
~/tmp
$ eval echo $TARGET_DIR
/home/jaypalsingh/tmp

Note: Make sure you read all the pros and cons of eval before considering it as an option.

Upvotes: 0

anubhava
anubhava

Reputation: 785108

You need:

TARGET_DIR=~/Downloads

i.e. keep tilde ~/ outside quote, otherwise shell won't expand it and ~ will be treated literally.

Upvotes: 4

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