Untar files using bazel

[Zain Asgar]

I am trying to create a rule (maybe one already exists?), to un-tar a file during a bazel build step. 

If I understand correctly all output files need to be known during the "Analysis Phase". To work around this I have a file lets call it manifest.txt which lists all the files in the tar file. However, I don't quite understand how I can read this file as a list outputs for my skylark rule? Is there an easy way to read a file and have each line be a generated output?

Thanks, 

- Zain

[Brian Silverman]

Zain,

If you reformat the manifest as something you can load, it's easy to work with it. That can't be quite one per line, but it can be close. I would do something like this (might not handle paths within the tar file too well without some more work):

manifest_foo.bzl:

contents = [

  'file1',

  'file2',

]

BUILD:

load(':manifest_foo.bzl', foo_contents = 'contents')

genrule(

  name = 'extract_foo',

  srcs = ['foo.tar'],

  outs = foo_contents,

  cmd = 'tar -C $(@D) -xf $(location foo.tar)',

)

If you're going to use this a lot, definitely write a macro around it.

Feel free to ask if you have any questions about that,

Brian

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