How to separate variables from other text in bash

Question

Is this the way to separate variables from other text in bash:

${PROJECT}_${GITCOMMIT}.tar.gz

if PROJECT = test AND GITCOMMIT = 222

Will this give you test_222.tar.gz? When should you use braces {} when it comes to variables? Are there other ways to separate the variables in bash from text?

Are you asking how bash does it? Are you asking how to implement it yourself programatically? What exactly is the question? — Charles Duffy, Nov 03 '15 at 23:19

score 0 · Answer 1 · answered Nov 03 '15 at 23:13

0

Yes, that is the way to do it. Your question is garbled however; you've got an underscore between the two variable expressions, so you won't get "test" and "222" adjacent to eachother in the resulting string.

answered Nov 03 '15 at 23:13

Pointy

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score 0 · Answer 2 · answered Nov 03 '15 at 23:18

In general, the braces are how you delimit text in the variable name from following text. In you case,

$PROJECT$GITCOMMIT.tar.gz  # test222.tar.gz

would be sufficient, because the $ that starts GITCOMMIT can't be part of the preceding parameter name. (Same for the . just before tar; there can't be a variable named GITCOMMIT..) If $PROJECT were followed by literal text, the braces would be necessary:

$PROJECT_$GITCOMMIT.tar.gz  # WRONG: No variable PROJECT_
${PROJECT}_$GITCOMMIT.tar.gz # CORRECT: test_222.tar.gz

How to separate variables from other text in bash

2 Answers2