Cannot set environment variable before command

Question

I am trying to set a variable before calling a command in bash (on Mac):

BRANCH=test echo "$BRANCH"

But I get an empty echo.

printenv also has no other variable with the same name:

$ printenv | grep BRANCH
$

What am I doing wrong?

anubhava · Accepted Answer · 2014-12-15 10:20:47Z

4

This is correct way:

BRANCH='test' bash -c 'echo "$BRANCH"'
test

To execute echo command you'll need bash -c to execute it after assignment.

answered Dec 15, 2014 at 10:20

anubhava

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What is the difference between BRANCH='test' bash -c 'echo "$BRANCH"' and BRANCH='test' echo "$BRANCH"?
– Gabriel Petrovay
Commented Dec 15, 2014 at 10:49
You could also use: ( BRANCH='test' && echo "$BRANCH" ) I guess in first case assignment isn't processed unless bash -c forks a new sub-process.
– anubhava
Commented Dec 15, 2014 at 10:56
1

I guess this answer explains it well.
– Gabriel Petrovay
Commented Dec 15, 2014 at 11:02
Two things to note: first, $BRANCH is expanded before echo starts, before echo could look in its environment. Second, echo ignores its environment anyway. There's no need or ability to use an environment variable here, so just use echo test.
– chepner
Commented Dec 15, 2014 at 15:57

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