genrule cmd with multiline string

[Hu David]

Hi,

I would like to have multiline string in genrule's cmd.

I tried many but cannot find the correct way to do this.

genrule(

  .....

  cmd = """ echo 123 &&

                  echo abc &&

                  echo def """,

)

Any ideas? Thanks.

David

[Kamal Marhubi]

You want to have a lot of string appends, sadly. Eg, https://github.com/kamalmarhubi/sqlite3-bazel/blob/use-strip-prefix/BUILD.sqlite3#L20

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[Kamal Marhubi]

(Alternatively, take it all and put it in a script, which you include in the tools attribute.)

[Brian Silverman]

I think you need to get rid of the '&&'s. The whole string (including the '\n's in the middle) gets passed into the shell at once, which means each line is actually a separate line.

In general, I've found '\n'.join([

  'echo 123',

  'echo %s' % 'abc',

]) to be the nicest approach, both for specifying the command directly and as the contents to put into a file if it gets too big.

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[Hu David]

Thanks. I'll try both.

[Hu David]

Kamal Marhubi,

I checked your genrule, what is the purpose of having the parenthesis in Line 23?

If I remove the parenthesis, the copy command next to it will fail. Why is it?

Thanks.

[Kamal Marhubi]

David—the parens run that command in a subshell, and that way the change of directory doesn't affect the rest of the command. Without the parens, the cp is running in the wrong directory. I hadn't looked at this before since I was just porting it from the makefile, so thanks for pointing it out! :-)

-Kamal

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[Alex Humesky]

Multiline strings should work in the genrule:

genrule(

  name = "gen_txt",

  outs = ["text.txt"],

  cmd = """

echo "hello world" > $@ && \

echo "hello world" >> $@

""")

then:

$ bazel build :gen_txt

INFO: Found 1 target...

Target //:gen_txt up-to-date:

  bazel-genfiles/text.txt

INFO: Elapsed time: 0.418s, Critical Path: 0.06s

$ cat bazel-genfiles/text.txt 

hello world

hello world

You may have been missing the backslash to escape the new lines for the shell, although this also worked for me:

  cmd = """

echo "hello world" > $@

echo "hello world" >> $@

"""

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[Alex Humesky]

If your error was "not all outputs were created" or similar, then you just needed to write the output to the outs file or files. If there is one output file, you can use $@ as in the above example. See http://bazel.io/docs/build-encyclopedia.html#genrule.cmd for more details.

[Kamal Marhubi]

Alex—thanks for pointing that out! Much nicer: https://github.com/kamalmarhubi/sqlite3-bazel/commit/be300352663681bea76dac204f999d6f5186ea3a

[Alex Humesky]

Note if the command to the genrule gets complicated enough, it may make sense to move the command into a .sh file, write a sh_binary rule, include the sh_binary in the tools attribute of the genrule, and then execute the binary in the genrule command. (py_binary, java_binary, etc, will also work). Then you don't have to have all the ampersands and escaping

[Hu David]

Alex,

I found that my BUILD files were \r\n line break thus I cannot use the following:

cmd = """

echo "hello world" > $@

echo "hello world" >> $@

"""

I fix this by transform the line break to the unix style.

Now, I can use this clean syntax. Thanks.

[Kamal Marhubi]

On Tue, Oct 13, 2015 at 2:46 PM Alex Humesky <ahum...@google.com> wrote:

Note if the command to the genrule gets complicated enough, it may make sense to move the command into a .sh file, write a sh_binary rule, include the sh_binary in the tools attribute of the genrule

I would probably do this, except that build files for new external repositories cannot refer to targets inside the main repo (yet?).

For now the multiline string is a huge improvement. For some reason I thought they weren't available in the strange Python subset that is the BUILD language.

[Lukács T. Berki]

On Wed, Oct 14, 2015 at 6:45 PM, Kamal Marhubi <ka...@marhubi.com> wrote:

On Tue, Oct 13, 2015 at 2:46 PM Alex Humesky <ahum...@google.com> wrote:

Note if the command to the genrule gets complicated enough, it may make sense to move the command into a .sh file, write a sh_binary rule, include the sh_binary in the tools attribute of the genrule

I would probably do this, except that build files for new external repositories cannot refer to targets inside the main repo (yet?).

Now the can :) The corresponding label syntax is "@//foo:bar" . 

For now the multiline string is a huge improvement. For some reason I thought they weren't available in the strange Python subset that is the BUILD language.

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[Kamal Marhubi]

Oh interesting! Now I just need to think about where it makes sense to put the BUILD files and any other scripts. Probably makes sense under third_party.