How to use Scala string interpolation to parameterize bash scripts?

Question

I'd like to compile a bash script from within Scala. To ease this I'd like to use string interpolation. However bash variables and Scala string interpolation don't seem to play well with each other. Here's an example

val someFile="test.txt"

val bashScript = s"""
newFile=${someFile}.filtered
grep foobar $someFile > $newFile
"""

This will result in a compile error because $newFile can not be interpolated. However, literally keeping $newFile as it is would give the expected valid bash script.

Possible solutions have crossed my mind, but I don't know if they are feasible nor how to implement them

Tell scala to use a different prefix for the interpolated expression, e.g. by implementing a custom interpolator
Somehow ignore non-interpolatable expressions and keep them as they are.

Have a look at Ammonite-Ops then you dont have to use BASH at all lihaoyi.github.io/Ammonite/#Ammonite-Ops — oluies
– oluies, Commented Nov 7, 2015 at 15:10

Reactormonk · Accepted Answer · 2015-11-06 10:45:04Z

3

The escape character for string interpolation is $, so

val someFile="test.txt"

val bashScript = s"""
newFile=${someFile}.filtered
grep foobar $someFile > $$newFile
"""

should do what you want.

answered Nov 6, 2015 at 10:45

Reactormonk

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moem · Accepted Answer · 2015-11-06 10:50:31Z

1

You can escape the dollar sign by adding a second dollar sign. So the following should work.

val someFile="test.txt"

val bashScript = s"""
  newFile=${someFile}.filtered
  grep foobar $someFile > $$newFile
"""

answered Nov 6, 2015 at 10:50

moem

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