How to call a bat / cmd file from Cygwin and inherit the variables?

Question

Suppose I have a bat (or cmd) script that sets an environment variable:

rem set_foo.bat
SET foo=XXX

I want to call that script from a Cygwin bash script, in such a way that the variable set by set_foo.bat is visible by the Cygwin bash script. That is, this Cygwin bash script:

#!/bin/sh
<call set_foo.bat in such a way that FOO becomes visible to this Cygwin script>
echo FOO is ${FOO}

should print:

FOO is XXX

Is this possible, and how?

PS 1: I am aware of the solutions proposed here: cygwin environment variables set in bat file, and they are NOT what I want.

PS 2: The bat script is not under my control (the Cygwin bash script is), so any solution that involves tweaking the bat script is not acceptable.

PS 3: If I just call set_foo.bat from the Cygwin bash script like this:

#!/bin/sh
set_foo.bat
echo FOO is ${FOO}

then the value of FOO is not visible. That is, the Cygwin bash script prints:

FOO is

[duplicate](https://stackoverflow.com/q/10552812). You should define the variables in batch file needs `SET foo=XXX` to have a variable `%foo%` instead of `%foo %`. Please flag it yourself; no flags remaining for me :(. — double-beep, Feb 02 '19 at 19:30
Without seeing the rest of the batch script, it's hard to say. If the script enables delayed expansion, you're out of luck, as that sandboxes the script's environment. — SomethingDark, Feb 02 '19 at 19:52
@SomethingDark What if the bat script does not enable delayed expansion? — user1387866, Feb 02 '19 at 20:00
Then as long as you call both scripts using the same command prompt, you should have access to it. — SomethingDark, Feb 02 '19 at 21:16

rojo · Accepted Answer · 2019-02-02T23:59:23.213

2

Try this:

#!/bin/sh

export $(cmd /c "set_foo.bat & set foo" | grep "^foo=")
echo Foo is $foo

As long as set_foo.bat doesn't set the value of %foo% within a setlocal scope, the value should carry over to the & set foo half of the cmd.exe-interpreted command. That will output the variable=value pair, which export will interpret as a native variable assignment.

edited Feb 02 '19 at 23:59

answered Feb 02 '19 at 23:17

rojo

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score 0 · Answer 2 · answered Feb 03 '19 at 20:55

Here is a simple working example. Make a cygwin shell script (with LF for EOL)

:
# runner.sh
cmd=/cygdrive/c/Windows/system32/cmd.exe
$cmd /C wrapper.bat
diff env0.txt env1.txt | dos2unix | sed -e '/[0-9]/d' -e '/^> /s/> //'

and a cmd script (with CR/LF for EOL)

@rem wrapper.bat
@set > env0.txt
@call .\set_foo.bat
@set > env1.txt

and a stand-in for the original cmd file (also with CR/LF for EOL)

@rem set_foo.bat
@set FOO=BAZ

Executing ./runner.sh from the shell will display environment variables set by the set_foo.bat cmd file. As long as that file does not use the setlocal command, you will see all environment changes in wrapper.bat. This should display new environment variables properly. Handling deletes or changes is left as an excercise for the reader, likewise passing in arguments.

HTH

How to call a bat / cmd file from Cygwin and inherit the variables?

2 Answers2