How to get the parent of a specific commit in Git

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

git log --pretty=%P -n 1 "$commit_from"

To get Parent Commit

git cat-file -p commit_id

tree tree_id
parent parent_commit_id
[parent other_parent_commit_id] # present only in case of merge commits
author xxx <xxx@email.com> 1513768542 +0530
committer xxx <xxx@email.com> 1513768542 +0530 

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}^

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).

To get the parent, just add a ^ after the commit SHA of the commit you want to see.

To see a commit: git show <SHA> Example: git show bb05425c504575145d005c0a887e0a80b885ced0

To see the parent: git show <SHA>^
Example: git show bb05425c504575145d005c0a887e0a80b885ced0^

If you are looking for the parent of a merge commit

# Output sha of the first parent
git rev-parse $commit^1

# Output sha of the second parent
git rev-parse $commit^2

# All parents sha
git rev-parse $commit^@

If trying to get all parents and using revision parameter syntax, you may try using log subcommand with --no-walk option.

An example, if we have the following:

$ git --oneline --graph
*   A
|\
| * B
| * C
| * D
* |   E

In this example, I'll use ^@ to get all parents and the --no-walk option to show only the parents and not their ancestors.

$ git log --no-walk A^@
commit B
	........

commit E
	........

Check out git rev-parse for more detail about revision parameter.

For the full details: git log 4c7036e807fa18a3e21a5182983c7c0f05c5936e^ -1

For just the hash: git log 4c7036e807fa18a3e21a5182983c7c0f05c5936e^ -1 --pretty=%H

The most efficient way

With git rev-parse <commit-ish>^@, parents will be displayed on a different line, making it easy to both view and parse.

Be careful not to use <commit-ish>^, this will only show the first parent, not the parents.

Other ways to inventory

Replacing -pretty=%P below with -pretty=raw will also work, the latter will show more content.

1. git cat-file -p <commit-ish>^{}.
2. git show -p <commit-ish>^{} --pretty=%P --no-patch.
3. git log --pretty=%P -n 1 <commit-ish>.
4. git rev-list --parents -n 1 <commit-ish>.

If you only want the ids of the parents of an input commit with id <SHA> then run this command:

git cat-file -p <SHA> | awk 'NR > 1 {if(/^parent/){print $2; next}{exit}}'

This will work for normal and shallow clones.

The previous commit of a commit can be reached also using the ~ notation:

git log aabbccdd~1

 curl \
  -H "Accept: application/vnd.github.v3+json" \
  https://api.github.com/repos/vadz/libtiff/commits/1ad0b2b5d3f1bd8bfe34d81e7742966cffeab6eb

...
  "parents": [
    {
      "sha": "86a4d8ea94037f4b440caef8f5e4466adb99c536",
      "url": "https://api.github.com/repos/vadz/libtiff/commits/86a4d8ea94037f4b440caef8f5e4466adb99c536",
      "html_url": "https://github.com/vadz/libtiff/commit/86a4d8ea94037f4b440caef8f5e4466adb99c536"
    }
  ],
...