Bash - making decisions based upon output? - bash

Question

I am scripting a lot of processes in BASH. I want to not build certain items if they are already up to date in Git.
if a git pull is issued and the results are something like:
Already on 'master'
Your branch is up-to-date with 'origin/master'.
From https://github.com/xxx/yyyy
* branch master -> FETCH_HEAD
Already up-to-date.
How can I base decisions on the output of git pull?
Attempts:
upstream ⚡ master) 17≡ $ git status
On branch master
nothing to commit, working tree clean
(upstream ⚡ master) 17≡ $ git pull origin master
From github.com:xxx/yyy m
* branch master -> FETCH_HEAD
Already up to date.
(upstream ⚡ master) 17≡ $ git pull origin master 2>/dev/null |grep -q "Already up-to-date"
(upstream ⚡ master) 17≡ $
Attempt 2:
$ git pull origin master 2>/dev/null | grep -q "Already up-to-date"; echo $?
1
$
Attempt 3:
$ git pull origin master 2>/dev/null |grep -q "Already up-to-date"; echo $?
1
$ git pull origin master
From github.com:cocos2d/cocos2d-x-docs
* branch master -> FETCH_HEAD
Already up to date.
$ git status
On branch master
nothing to commit, working tree clean
$ git pull origin master 2>/dev/null |grep -q "Already up-to-date"; echo $?
1
Attempt 4:
$ git pull origin master 2>/dev/null |cat
Already up to date.
$ git pull origin master 2>/dev/null | grep -q "Already up-to-date"; echo $?
1

Answer 1

This will return true (0) if the output of git pull contains Already up-to-date:
git pull | grep -q "Already up-to-date"
Then you can put it into an if-statement to take action conditionally. For example:
if git pull | grep -q "Already up-to-date"; then
echo "Building stuff"
else
echo "Not building stuff"
fi
Your attempts are failing because git is printing up to date without the dashes, but the grep command is searching for up-to-date with the dashes, which is what your example output says. (BTW I'm using git 2.7.4 which prints up-to-date.) This sort of output might change between versions of git, so there is a more stable way of checking this sort of output, but I'm not sure what it is :/