How to get parent of specific commit in Git?

Question

I have commit number. I would like to get previous commit number(parent). I need commits from current branch.

Answer 1

If ${SHA} is the commit you know and you want its parent (assuming it's not a merge commit and has only one parent):

git rev-parse ${SHA}^

Answer 2

You can use git rev-parse for this.

# Output hash of the first parent
git rev-parse $commit^

# Nth parent
git rev-parse $commit^N

# All parents
git rev-parse $commit^@

These constructs are explained in git help rev-parse:

 <rev>^, e.g. HEAD^, v1.5.1^0
     A suffix ^ to a revision parameter means the first
     parent of that commit object.  ^<n> means the <n>th
     parent (i.e.  <rev>^ is equivalent to <rev>^1). As a
     special rule, <rev>^0 means the commit itself and is
     used when <rev> is the object name of a tag object that
     refers to a commit object.

 ...

 <rev>^@, e.g. HEAD^@
     A suffix ^ followed by an at sign is the same as listing
     all parents of <rev> (meaning, include anything
     reachable from its parents, but not the commit itself).