manpagez: man pages & more
man perlgit(1)
Home | html | info | man
PERLGIT(1pm)           Perl Programmers Reference Guide           PERLGIT(1pm)


       perlgit - Detailed information about git and the Perl repository


       This document provides details on using git to develop Perl. If you are
       just interested in working on a quick patch, see perlhack first.  This
       document is intended for people who are regular contributors to Perl,
       including those with write access to the git repository.


       All of Perl's source code is kept centrally in a Git repository at

       You can make a read-only clone of the repository by running:

         % git clone git:// perl

       This uses the git protocol (port 9418).

       If you cannot use the git protocol for firewall reasons, you can also
       clone via http:

         % git clone perl


       Once you have changed into the repository directory, you can inspect
       it. After a clone the repository will contain a single local branch,
       which will be the current branch as well, as indicated by the asterisk.

         % git branch
         * blead

       Using the -a switch to "branch" will also show the remote tracking
       branches in the repository:

         % git branch -a
         * blead

       The branches that begin with "origin" correspond to the "git remote"
       that you cloned from (which is named "origin"). Each branch on the
       remote will be exactly tracked by these branches. You should NEVER do
       work on these remote tracking branches. You only ever do work in a
       local branch. Local branches can be configured to automerge (on pull)
       from a designated remote tracking branch. This is the case with the
       default branch "blead" which will be configured to merge from the
       remote tracking branch "origin/blead".

       You can see recent commits:

         % git log

       And pull new changes from the repository, and update your local
       repository (must be clean first)

         % git pull

       Assuming we are on the branch "blead" immediately after a pull, this
       command would be more or less equivalent to:

         % git fetch
         % git merge origin/blead

       In fact if you want to update your local repository without touching
       your working directory you do:

         % git fetch

       And if you want to update your remote-tracking branches for all defined
       remotes simultaneously you can do

         % git remote update

       Neither of these last two commands will update your working directory,
       however both will update the remote-tracking branches in your

       To make a local branch of a remote branch:

         % git checkout -b maint-5.10 origin/maint-5.10

       To switch back to blead:

         % git checkout blead

   Finding out your status
       The most common git command you will use will probably be

         % git status

       This command will produce as output a description of the current state
       of the repository, including modified files and unignored untracked
       files, and in addition it will show things like what files have been
       staged for the next commit, and usually some useful information about
       how to change things. For instance the following:

        % git status
        On branch blead
        Your branch is ahead of 'origin/blead' by 1 commit.

        Changes to be committed:
          (use "git reset HEAD <file>..." to unstage)

              modified:   pod/perlgit.pod

        Changes not staged for commit:
          (use "git add <file>..." to update what will be committed)
          (use "git checkout -- <file>..." to discard changes in working

              modified:   pod/perlgit.pod

        Untracked files:
          (use "git add <file>..." to include in what will be committed)


       This shows that there were changes to this document staged for commit,
       and that there were further changes in the working directory not yet
       staged. It also shows that there was an untracked file in the working
       directory, and as you can see shows how to change all of this. It also
       shows that there is one commit on the working branch "blead" which has
       not been pushed to the "origin" remote yet. NOTE: This output is also
       what you see as a template if you do not provide a message to "git

   Patch workflow
       First, please read perlhack for details on hacking the Perl core.  That
       document covers many details on how to create a good patch.

       If you already have a Perl repository, you should ensure that you're on
       the blead branch, and your repository is up to date:

         % git checkout blead
         % git pull

       It's preferable to patch against the latest blead version, since this
       is where new development occurs for all changes other than critical bug
       fixes. Critical bug fix patches should be made against the relevant
       maint branches, or should be submitted with a note indicating all the
       branches where the fix should be applied.

       Now that we have everything up to date, we need to create a temporary
       new branch for these changes and switch into it:

         % git checkout -b orange

       which is the short form of

         % git branch orange
         % git checkout orange

       Creating a topic branch makes it easier for the maintainers to rebase
       or merge back into the master blead for a more linear history. If you
       don't work on a topic branch the maintainer has to manually cherry pick
       your changes onto blead before they can be applied.

       That'll get you scolded on perl5-porters, so don't do that. Be Awesome.

       Then make your changes. For example, if Leon Brocard changes his name
       to Orange Brocard, we should change his name in the AUTHORS file:

         % perl -pi -e 's{Leon Brocard}{Orange Brocard}' AUTHORS

       You can see what files are changed:

         % git status
         On branch orange
         Changes to be committed:
           (use "git reset HEAD <file>..." to unstage)

            modified:   AUTHORS

       And you can see the changes:

        % git diff
        diff --git a/AUTHORS b/AUTHORS
        index 293dd70..722c93e 100644
        --- a/AUTHORS
        +++ b/AUTHORS
        @@ -541,7 +541,7 @@    Lars Hecking              <>
         Laszlo Molnar                  <>
         Leif Huhn                      <>
         Len Johnson                    <>
        -Leon Brocard                   <>
        +Orange Brocard                 <>
         Les Peters                     <>
         Lesley Binks                   <>
         Lincoln D. Stein               <>

       Now commit your change locally:

        % git commit -a -m 'Rename Leon Brocard to Orange Brocard'
        Created commit 6196c1d: Rename Leon Brocard to Orange Brocard
         1 files changed, 1 insertions(+), 1 deletions(-)

       The "-a" option is used to include all files that git tracks that you
       have changed. If at this time, you only want to commit some of the
       files you have worked on, you can omit the "-a" and use the command
       "git add FILE ..." before doing the commit. "git add --interactive"
       allows you to even just commit portions of files instead of all the
       changes in them.

       The "-m" option is used to specify the commit message. If you omit it,
       git will open a text editor for you to compose the message
       interactively. This is useful when the changes are more complex than
       the sample given here, and, depending on the editor, to know that the
       first line of the commit message doesn't exceed the 50 character legal
       maximum. See "Commit message" in perlhack for more information about
       what makes a good commit message.

       Once you've finished writing your commit message and exited your
       editor, git will write your change to disk and tell you something like

        Created commit daf8e63: explain git status and stuff about remotes
         1 files changed, 83 insertions(+), 3 deletions(-)

       If you re-run "git status", you should see something like this:

        % git status
        On branch orange
        Untracked files:
          (use "git add <file>..." to include in what will be committed)


        nothing added to commit but untracked files present (use "git add" to

       When in doubt, before you do anything else, check your status and read
       it carefully, many questions are answered directly by the git status

       You can examine your last commit with:

         % git show HEAD

       and if you are not happy with either the description or the patch
       itself you can fix it up by editing the files once more and then issue:

         % git commit -a --amend

       Now, create a fork on GitHub to push your branch to, and add it as a
       remote if you haven't already, as described in the GitHub documentation
       at <>:

         % git remote add fork

       And push the branch to your fork:

         % git push -u fork orange

       You should now submit a Pull Request (PR) on GitHub from the new branch
       to blead. For more information, see the GitHub documentation at

       You can also send patch files to
       <> directly if the patch is not ready to
       be applied, but intended for discussion.

       To create a patch file for all your local changes:

         % git format-patch -M blead..

       Or for a lot of changes, e.g. from a topic branch:

         % git format-patch --stdout -M blead.. > topic-branch-changes.patch

       If you want to delete your temporary branch, you may do so with:

        % git checkout blead
        % git branch -d orange
        error: The branch 'orange' is not an ancestor of your current HEAD.
        If you are sure you want to delete it, run 'git branch -D orange'.
        % git branch -D orange
        Deleted branch orange.

   A note on derived files
       Be aware that many files in the distribution are derivative--avoid
       patching them, because git won't see the changes to them, and the build
       process will overwrite them. Patch the originals instead. Most
       utilities (like perldoc) are in this category, i.e. patch
       utils/perldoc.PL rather than utils/perldoc. Similarly, don't create
       patches for files under $src_root/ext from their copies found in
       $install_root/lib. If you are unsure about the proper location of a
       file that may have gotten copied while building the source
       distribution, consult the MANIFEST.

   Cleaning a working directory
       The command "git clean" can with varying arguments be used as a
       replacement for "make clean".

       To reset your working directory to a pristine condition you can do:

         % git clean -dxf

       However, be aware this will delete ALL untracked content. You can use

         % git clean -Xf

       to remove all ignored untracked files, such as build and test
       byproduct, but leave any manually created files alone.

       If you only want to cancel some uncommitted edits, you can use "git
       checkout" and give it a list of files to be reverted, or "git checkout
       -f" to revert them all.

       If you want to cancel one or several commits, you can use "git reset".

       "git" provides a built-in way to determine which commit should be
       blamed for introducing a given bug. "git bisect" performs a binary
       search of history to locate the first failing commit. It is fast,
       powerful and flexible, but requires some setup and to automate the
       process an auxiliary shell script is needed.

       The core provides a wrapper program, Porting/, which attempts
       to simplify as much as possible, making bisecting as simple as running
       a Perl one-liner. For example, if you want to know when this became an

           perl -e 'my $a := 2'

       you simply run this:

           .../Porting/ -e 'my $a := 2;'

       Using Porting/, with one command (and no other files) it's
       easy to find out

       o   Which commit caused this example code to break?

       o   Which commit caused this example code to start working?

       o   Which commit added the first file to match this regex?

       o   Which commit removed the last file to match this regex?

       usually without needing to know which versions of perl to use as start
       and end revisions, as Porting/ automatically searches to find
       the earliest stable version for which the test case passes. Run
       "Porting/ --help" for the full documentation, including how to
       set the "Configure" and build time options.

       If you require more flexibility than Porting/ has to offer,
       you'll need to run "git bisect" yourself. It's most useful to use "git
       bisect run" to automate the building and testing of perl revisions. For
       this you'll need a shell script for "git" to call to test a particular
       revision. An example script is Porting/, which you
       should copy outside of the repository, as the bisect process will reset
       the state to a clean checkout as it runs. The instructions below assume
       that you copied it as ~/run and then edited it as appropriate.

       You first enter in bisect mode with:

         % git bisect start

       For example, if the bug is present on "HEAD" but wasn't in 5.10.0,
       "git" will learn about this when you enter:

         % git bisect bad
         % git bisect good perl-5.10.0
         Bisecting: 853 revisions left to test after this

       This results in checking out the median commit between "HEAD" and
       "perl-5.10.0". You can then run the bisecting process with:

         % git bisect run ~/run

       When the first bad commit is isolated, "git bisect" will tell you so:

         ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5 is first bad commit
         commit ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5
         Author: Dave Mitchell <>
         Date:   Sat Feb 9 14:56:23 2008 +0000

             [perl #49472] Attributes + Unknown Error

         bisect run success

       You can peek into the bisecting process with "git bisect log" and "git
       bisect visualize". "git bisect reset" will get you out of bisect mode.

       Please note that the first "good" state must be an ancestor of the
       first "bad" state. If you want to search for the commit that solved
       some bug, you have to negate your test case (i.e. exit with 1 if OK and
       0 if not) and still mark the lower bound as "good" and the upper as
       "bad". The "first bad commit" has then to be understood as the "first
       commit where the bug is solved".

       "git help bisect" has much more information on how you can tweak your
       binary searches.

       Following bisection you may wish to configure, build and test perl at
       commits identified by the bisection process.  Sometimes, particularly
       with older perls, "make" may fail during this process.  In this case
       you may be able to patch the source code at the older commit point.  To
       do so, please follow the suggestions provided in "Building perl at
       older commits" in perlhack.

   Topic branches and rewriting history
       Individual committers should create topic branches under

         % branch="$yourname/$some_descriptive_name"
         % git checkout -b $branch
         ... do local edits, commits etc ...
         % git push origin -u $branch

       Should you be stuck with an ancient version of git (prior to 1.7), then
       "git push" will not have the "-u" switch, and you have to replace the
       last step with the following sequence:

         % git push origin $branch:refs/heads/$branch
         % git config branch.$branch.remote origin
         % git config branch.$branch.merge refs/heads/$branch

       If you want to make changes to someone else's topic branch, you should
       check with its creator before making any change to it.

       You might sometimes find that the original author has edited the
       branch's history. There are lots of good reasons for this. Sometimes,
       an author might simply be rebasing the branch onto a newer source
       point.  Sometimes, an author might have found an error in an early
       commit which they wanted to fix before merging the branch to blead.

       Currently the master repository is configured to forbid non-fast-
       forward merges. This means that the branches within can not be rebased
       and pushed as a single step.

       The only way you will ever be allowed to rebase or modify the history
       of a pushed branch is to delete it and push it as a new branch under
       the same name. Please think carefully about doing this. It may be
       better to sequentially rename your branches so that it is easier for
       others working with you to cherry-pick their local changes onto the new
       version. (XXX: needs explanation).

       If you want to rebase a personal topic branch, you will have to delete
       your existing topic branch and push as a new version of it. You can do
       this via the following formula (see the explanation about "refspec"'s
       in the git push documentation for details) after you have rebased your

         # first rebase
         % git checkout $user/$topic
         % git fetch
         % git rebase origin/blead

         # then "delete-and-push"
         % git push origin :$user/$topic
         % git push origin $user/$topic

       NOTE: it is forbidden at the repository level to delete any of the
       "primary" branches. That is any branch matching
       "m!^(blead|maint|perl)!". Any attempt to do so will result in git
       producing an error like this:

         % git push origin :blead
         *** It is forbidden to delete blead/maint branches in this repository
         error: hooks/update exited with error code 1
         error: hook declined to update refs/heads/blead
         To ssh://
          ! [remote rejected] blead (hook declined)
          error: failed to push some refs to 'ssh://'

       As a matter of policy we do not edit the history of the blead and
       maint-* branches. If a typo (or worse) sneaks into a commit to blead or
       maint-*, we'll fix it in another commit. The only types of updates
       allowed on these branches are "fast-forwards", where all history is

       Annotated tags in the canonical perl.git repository will never be
       deleted or modified. Think long and hard about whether you want to push
       a local tag to perl.git before doing so. (Pushing simple tags is not

       The perl history contains one mistake which was not caught in the
       conversion: a merge was recorded in the history between blead and
       maint-5.10 where no merge actually occurred. Due to the nature of git,
       this is now impossible to fix in the public repository. You can remove
       this mis-merge locally by adding the following line to your
       ".git/info/grafts" file:

        296f12bbbbaa06de9be9d09d3dcf8f4528898a49 434946e0cb7a32589ed92d18008aaa1d88515930

       It is particularly important to have this graft line if any bisecting
       is done in the area of the "merge" in question.


       Once you have write access, you will need to modify the URL for the
       origin remote to enable pushing. Edit .git/config with the
       git-config(1) command:

         % git config remote.origin.url

       You can also set up your user name and e-mail address. Most people do
       this once globally in their ~/.gitconfig by doing something like:

         % git config --global "AEvar Arnfjoer` Bjarmason"
         % git config --global

       However, if you'd like to override that just for perl, execute
       something like the following in perl:

         % git config

       It is also possible to keep "origin" as a git remote, and add a new
       remote for ssh access:

         % git remote add camel

       This allows you to update your local repository by pulling from
       "origin", which is faster and doesn't require you to authenticate, and
       to push your changes back with the "camel" remote:

         % git fetch camel
         % git push camel

       The "fetch" command just updates the "camel" refs, as the objects
       themselves should have been fetched when pulling from "origin".

   Working with Github pull requests
       Pull requests typically originate from outside of the "Perl/perl.git"
       repository, so if you want to test or work with it locally a vanilla
       "git fetch" from the "Perl/perl5.git" repository won't fetch it.

       However Github does provide a mechanism to fetch a pull request to a
       local branch.  They are available on Github remotes under "pull/", so
       you can use "git fetch pull/PRID/head:localname" to make a local copy.
       eg.  to fetch pull request 9999 to the local branch "local-branch-name"

         git fetch origin pull/9999/head:local-branch-name

       and then:

         git checkout local-branch-name

       Note: this branch is not rebased on "blead", so instead of the checkout
       above, you might want:

         git rebase origin/blead local-branch-name

       which rebases "local-branch-name" on "blead", and checks it out.

       Alternatively you can configure the remote to fetch all pull requests
       as remote-tracking branches.  To do this edit the remote in
       .git/config, for example if your github remote is "origin" you'd have:

         [remote "origin"]
                 url =
                 fetch = +refs/heads/*:refs/remotes/origin/*

       Add a line to map the remote pull request branches to remote-tracking

         [remote "origin"]
                 url =
                 fetch = +refs/heads/*:refs/remotes/origin/*
                 fetch = +refs/pull/*/head:refs/remotes/origin/pull/*

       and then do a fetch as normal:

         git fetch origin

       This will create a remote-tracking branch for every pull request,
       including closed requests.

       To remove those remote-tracking branches, remove the line added above
       and prune:

         git fetch -p origin # or git remote prune origin

   Accepting a patch
       If you have received a patch file generated using the above section,
       you should try out the patch.

       First we need to create a temporary new branch for these changes and
       switch into it:

        % git checkout -b experimental

       Patches that were formatted by "git format-patch" are applied with "git

        % git am 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch
        Applying Rename Leon Brocard to Orange Brocard

       Note that some UNIX mail systems can mess with text attachments
       containing 'From '. This will fix them up:

        % perl -pi -e's/^>From /From /' \

       If just a raw diff is provided, it is also possible use this two-step

        % git apply bugfix.diff
        % git commit -a -m "Some fixing" \
                                   --author="That Guy <>"

       Now we can inspect the change:

        % git show HEAD
        commit b1b3dab48344cff6de4087efca3dbd63548ab5e2
        Author: Leon Brocard <>
        Date:   Fri Dec 19 17:02:59 2008 +0000

          Rename Leon Brocard to Orange Brocard

        diff --git a/AUTHORS b/AUTHORS
        index 293dd70..722c93e 100644
        --- a/AUTHORS
        +++ b/AUTHORS
        @@ -541,7 +541,7 @@ Lars Hecking                 <>
         Laszlo Molnar                  <>
         Leif Huhn                      <>
         Len Johnson                    <>
        -Leon Brocard                   <>
        +Orange Brocard                 <>
         Les Peters                     <>
         Lesley Binks                   <>
         Lincoln D. Stein               <>

       If you are a committer to Perl and you think the patch is good, you can
       then merge it into blead then push it out to the main repository:

         % git checkout blead
         % git merge experimental
         % git push origin blead

       If you want to delete your temporary branch, you may do so with:

        % git checkout blead
        % git branch -d experimental
        error: The branch 'experimental' is not an ancestor of your current
        HEAD.  If you are sure you want to delete it, run 'git branch -D
        % git branch -D experimental
        Deleted branch experimental.

   Committing to blead
       The 'blead' branch will become the next production release of Perl.

       Before pushing any local change to blead, it's incredibly important
       that you do a few things, lest other committers come after you with
       pitchforks and torches:

       o   Make sure you have a good commit message. See "Commit message" in
           perlhack for details.

       o   Run the test suite. You might not think that one typo fix would
           break a test file. You'd be wrong. Here's an example of where not
           running the suite caused problems. A patch was submitted that added
           a couple of tests to an existing .t. It couldn't possibly affect
           anything else, so no need to test beyond the single affected .t,
           right?  But, the submitter's email address had changed since the
           last of their submissions, and this caused other tests to fail.
           Running the test target given in the next item would have caught
           this problem.

       o   If you don't run the full test suite, at least "make test_porting".
           This will run basic sanity checks. To see which sanity checks, have
           a look in t/porting.

       o   If you make any changes that affect miniperl or core routines that
           have different code paths for miniperl, be sure to run "make
           minitest".  This will catch problems that even the full test suite
           will not catch because it runs a subset of tests under miniperl
           rather than perl.

   On merging and rebasing
       Simple, one-off commits pushed to the 'blead' branch should be simple
       commits that apply cleanly.  In other words, you should make sure your
       work is committed against the current position of blead, so that you
       can push back to the master repository without merging.

       Sometimes, blead will move while you're building or testing your
       changes.  When this happens, your push will be rejected with a message
       like this:

        To ssh://
         ! [rejected]        blead -> blead (non-fast-forward)
        error: failed to push some refs to 'ssh://'
        To prevent you from losing history, non-fast-forward updates were
        rejected Merge the remote changes (e.g. 'git pull') before pushing
        again.  See the 'Note about fast-forwards' section of 'git push --help'
        for details.

       When this happens, you can just rebase your work against the new
       position of blead, like this (assuming your remote for the master
       repository is "p5p"):

         % git fetch p5p
         % git rebase p5p/blead

       You will see your commits being re-applied, and you will then be able
       to push safely.  More information about rebasing can be found in the
       documentation for the git-rebase(1) command.

       For larger sets of commits that only make sense together, or that would
       benefit from a summary of the set's purpose, you should use a merge
       commit.  You should perform your work on a topic branch, which you
       should regularly rebase against blead to ensure that your code is not
       broken by blead moving.  When you have finished your work, please
       perform a final rebase and test.  Linear history is something that gets
       lost with every commit on blead, but a final rebase makes the history
       linear again, making it easier for future maintainers to see what has
       happened.  Rebase as follows (assuming your work was on the branch

         % git checkout committer/somework
         % git rebase blead

       Then you can merge it into master like this:

         % git checkout blead
         % git merge --no-ff --no-commit committer/somework
         % git commit -a

       The switches above deserve explanation.  "--no-ff" indicates that even
       if all your work can be applied linearly against blead, a merge commit
       should still be prepared.  This ensures that all your work will be
       shown as a side branch, with all its commits merged into the mainstream
       blead by the merge commit.

       "--no-commit" means that the merge commit will be prepared but not
       committed.  The commit is then actually performed when you run the next
       command, which will bring up your editor to describe the commit.
       Without "--no-commit", the commit would be made with nearly no useful
       message, which would greatly diminish the value of the merge commit as
       a placeholder for the work's description.

       When describing the merge commit, explain the purpose of the branch,
       and keep in mind that this description will probably be used by the
       eventual release engineer when reviewing the next perldelta document.

   Committing to maintenance versions
       Maintenance versions should only be altered to add critical bug fixes,
       see perlpolicy.

       To commit to a maintenance version of perl, you need to create a local
       tracking branch:

         % git checkout --track -b maint-5.005 origin/maint-5.005

       This creates a local branch named "maint-5.005", which tracks the
       remote branch "origin/maint-5.005". Then you can pull, commit, merge
       and push as before.

       You can also cherry-pick commits from blead and another branch, by
       using the "git cherry-pick" command. It is recommended to use the -x
       option to "git cherry-pick" in order to record the SHA1 of the original
       commit in the new commit message.

       Before pushing any change to a maint version, make sure you've
       satisfied the steps in "Committing to blead" above.

   Using a smoke-me branch to test changes
       Sometimes a change affects code paths which you cannot test on the OSes
       which are directly available to you and it would be wise to have users
       on other OSes test the change before you commit it to blead.

       Fortunately, there is a way to get your change smoke-tested on various
       OSes: push it to a "smoke-me" branch and wait for certain automated
       smoke-testers to report the results from their OSes.  A "smoke-me"
       branch is identified by the branch name: specifically, as seen on it must be a local branch whose first name component is
       precisely "smoke-me".

       The procedure for doing this is roughly as follows (using the example
       of tonyc's smoke-me branch called win32stat):

       First, make a local branch and switch to it:

         % git checkout -b win32stat

       Make some changes, build perl and test your changes, then commit them
       to your local branch. Then push your local branch to a remote smoke-me

         % git push origin win32stat:smoke-me/tonyc/win32stat

       Now you can switch back to blead locally:

         % git checkout blead

       and continue working on other things while you wait a day or two,
       keeping an eye on the results reported for your smoke-me branch at

       If all is well then update your blead branch:

         % git pull

       then checkout your smoke-me branch once more and rebase it on blead:

         % git rebase blead win32stat

       Now switch back to blead and merge your smoke-me branch into it:

         % git checkout blead
         % git merge win32stat

       As described earlier, if there are many changes on your smoke-me branch
       then you should prepare a merge commit in which to give an overview of
       those changes by using the following command instead of the last
       command above:

         % git merge win32stat --no-ff --no-commit

       You should now build perl and test your (merged) changes one last time
       (ideally run the whole test suite, but failing that at least run the
       t/porting/*.t tests) before pushing your changes as usual:

         % git push origin blead

       Finally, you should then delete the remote smoke-me branch:

         % git push origin :smoke-me/tonyc/win32stat

       (which is likely to produce a warning like this, which can be ignored:

        remote: fatal: ambiguous argument
        unknown revision or path not in the working tree.
        remote: Use '--' to separate paths from revisions

       ) and then delete your local branch:

         % git branch -d win32stat

perl v5.34.0                      2021-05-04                      PERLGIT(1pm)

perl 5.34.0 - Generated Sat Feb 26 05:35:09 CST 2022
© 2000-2024
Individual documents may contain additional copyright information.