Parse lines of output from bash loop

Question

I'm trying to parse the output of commands run in a bash loop. Here is an example:

$ for i in `git log --format='%H'`; do echo $i ; git branch --contains $i; done | head -n 8
5f11ce7da2f9a4c4899dc2e47b02c2d936d0468e
* foobar
e1c3f6fabd45715b527a083bc797e9723c57ac89
  dev1
* foobar
7053e08775d2c1da7480a988a235e445799cbca5
  dev1
* foobar

The command git log --format='%H' prints out only the commit ID for each Git commit. The command git branch --contains $i prints out which Git branches contain the commit.

I'm trying to find the latest git commit that is not on branch 'foobar'. I would like to echo $i for the first branch whose output of git branch --contains $i contains a line that does not start with the * character, which specifies "current branch". What Bash documentation should I be reading?

Note that I am aware of other solutions to this problem. However, I plan on making additions that the other answers do not account for. Furthermore, this is how I improve my Bash scripting abilities.

Solution

Something like this might be what you want.

for i in $(git log --format='%H'); do
    branch="$(git branch --contains $i|awk 'NR==1{print $1}')"
    [ "$branch" != "*" ] && echo "commit '$i' is in branch '$branch'"
done

Prints the commit and its branch if not the current branch.

Comments

[Arkadiusz Drabczyk]

You can achieve what you want in at least 2 ways - by grepping output of git branch --contains command or by checking how many lines this command returned with wc -l. In either way, you will likely need to use command substitution (you are already doing that but look up on differences between $() and backticks), [ command (type type [ and then help [), if or || or something similar, and break or exit to exit for loop.

[dotancohen]

@ArkadiuszDrabczyk: Thanks. With grep -v '^*' after the contains command I can get the name of the branch. Now, how might I output $i and break only when grep matches something?

[dotancohen]

Thank you! I was not sure how to use the [[]] if in this context though I had found it used elsewhere online. The use of awk is creative.

[John B]

No problem! The use of double braces here is actually not necessary, and it's a Bash only syntax that's only really required for using Bash regex =~ or glob comparisons against variables like case does with *. I've updated the post to use the single braces which makes it POSIX shell compliant.

[dotancohen]

I see, thanks. I'm looking at some of your older posts as well to learn some Bash as you give excellent examples. Thank you!