How to pass variables in a shell script as arguments?

Question

I have a shell script in which I am passing the same value many times as arguments. Instead of hardcoding this redundant value across all py scripts, I wanted to see if I can work with variables and pass those into the py script as arguments.

Here is the script.sh:

python A.py     --month=10
python B.py     --country=USA --month=10

I would like something like this:

#Setting variables to pass into args
country=USA
month=10

python A.py     --month=month
python B.py     --country=country --month=month

How would I do this?

Answer 1

To access the value of any variable in shell script, you can do it using the $ sign.

So below is how you can do it:

#Setting variables to pass into args
country=USA
month=10

python A.py     --month="$month"
python B.py     --country="$country" --month="$month"

Answer 2

If you have to use arguments passed to script, try something like below

script SomeMonth SomeCountry

Then in script

python A.py     --month="$1"
python B.py     --country="$2" --month="$1"

The positional parameters..

$0 = script (script Name)

$1 = SomeMonth (first argument)

$2 = SomeCountry (Second argument)

And so on..

Answer 3

Just to add something to the other correct answers. If you use those arguments many times, you can also embed the argument name together with its value, and save typing and errors:

# Setting variables to pass into args
p_country="--country=USA"
p_month="--month=10"

python A.py     $p_month
python B.py     $p_country $p_month

Note 1: beware of values containing spaces, or any other "strange" characters (meaningful to the shell). Ordinary words or numbers, like "USA" and "10" pose no problems.

Note 2: you can also store multiple "arg=value" in a single variable; it can save even more typing. For example:

  p_m_and_c="--country=USA --month=10"
  ...
  python B.py     $p_m_and_c