Question

I am trying to do a code walk through a badly written bash script.

I have come across this statement:

FOOBAR_NAME=`date +WeekNo.%W`

There are no prior declarations of any of the RHS variables in the script, lines preceding this statement.

So my question is:

What does FOOBAR_NAME resolve to, when it is used a few lines down in the script as $FOOBAR_NAME ?

Answer 1

There are no variables being referenced in the RHS.

The backtick operator (“ ) evaluates its contents and returns the output, similar (identical?) to$(). It's a quick way to write aneval` (in other languages).

Type date +WeekNo.%W in a shell. What is printed (in stdout, with newlines collapsed) is what will be stored in FOOBAR_NAME.

Note that the evaluation occurs only once, which is during the assignment. date isn’t executed each time you reference FOOBAR_NAME.