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View colored, incremental diff in a workspace or from stdin, with side by side and auto pager support

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Term based tool to view colored, incremental diff in a version controlled workspace (supports Git, Mercurial, Perforce and Svn so far) or from stdin, with side by side (similar to diff -y) and auto pager support. Requires python (>= 2.6.0) and less.

default side by side

Ydiff only supports diff in Unified Format. This is default in most version control system except Perforce, which needs an environment variable P4DIFF="diff -u" to output unified diff.


Ydiff only depends on Python built-in libraries, so you can just download the source and run without worrying about any installation.

Git tagged releases will be packaged and uploaded to PyPI timely, however, packages hosted elsewhere are not (please note they are not managed by the author @ymattw).

Download directly

Just save to whatever directory which is in your $PATH, for example, $HOME/bin is in my $PATH, so I save the script there and name as ydiff.

curl -ksSL > ~/bin/ydiff
chmod +x ~/bin/ydiff

Install with pip

Ydiff is already listed on PyPI, you can install with pip if you have the tool.

pip install --upgrade ydiff

Install with

You can also run the from the source if you don’t have pip.

git clone
cd ydiff
./ install

Install with Homebrew

You can also install with Homebrew on Mac. (Thanks to @josa42, @bfontaine, @hivehand and @nijikon for contributing to the Homebrew Formula).

brew install ydiff

Install on Fedora

On Fedora, you can install ydiff with dnf.

dnf install ydiff

Install on FreeBSD

On FreeBSD, you can install ydiff with pkg.

pkg install ydiff


Type ydiff -h to show usage:

$ ydiff -h
Usage: ydiff [options] [file|dir ...]

View colored, incremental diff in a workspace or from stdin, with side by side
and auto pager support

  --version            show program's version number and exit
  -h, --help           show this help message and exit
  -s, --side-by-side   enable side-by-side mode
  -w N, --width=N      set text width for side-by-side mode, 0 for auto
                       detection, default is 80
  -l, --log            show log with changes from revision control
  -c M, --color=M      colorize mode 'auto' (default), 'always', or 'never'
  -t N, --tab-width=N  convert tab characters to this many spaces (default: 8)
  --wrap               wrap long lines in side-by-side view
  -p M, --pager=M      pager application, suggested values are 'less' or 'cat'
  -o M, --pager-options=M
                       options to supply to pager application

    Option parser will stop on first unknown option and pass them down to
    underneath revision control. Environment variable YDIFF_OPTIONS may be
    used to specify default options that will be placed at the beginning
    of the argument list.

Read diff from local modification in a Git/Mercurial/Perforce/Svn workspace (output from e.g. git diff, svn diff):

cd proj-workspace
ydiff                         # view colored incremental diff
ydiff -s                      # view side by side, use default text width 80
ydiff -s -w 90                # use text width 90 other than default 80
ydiff -s -w 0                 # auto set text width based on terminal size
ydiff -s -w 0 --wrap          # same as before, but also wrap long lines
ydiff -s file1 dir2           # view modification of given files/dirs only
ydiff -s -w90 --wrap -- -U10  # pass '-U10' to underneath revision diff tool
ydiff -s -w90 --wrap -U10     # '--' is optional as it's unknown to ydiff
ydiff -s --cached             # show git staged diff (git diff --cached)
ydiff -s -r1234               # show svn diff to revision 1234

Read log with changes in a Git/Mercurial/Svn workspace (output from e.g. git log -p, svn log --diff), note –diff option is new in svn 1.7.0:

cd proj-workspace
ydiff -l                    # read log along with changes
ydiff -ls                   # equivalent to ydiff -l -s, view side by side
ydiff -ls -w90 --wrap       # set text width 90 and enable wrapping as well
ydiff -ls file1 dir2        # see log with changes of given files/dirs only

Utilize a specific pager application:

ydiff                           # default pager - less
LESS_OPTS='-FRSX --shift 1'
ydiff -p less -o "${LESS_OPTS}" # emulate default pager
ydiff -p /usr/bin/less          # custom pager
ydiff -p cat                    # non-paging ANSI processor for colorizing

Pipe in a diff:

git log -p -2 | ydiff       # view git log with changes of last 2 commits
git show 15bfa | ydiff -s   # view a given git commit, side by side
svn diff -r1234 | ydiff -s  # view svn diff comparing to given revision
diff -u file1 file2 | ydiff # view diff between two files (note the '-u')
diff -ur dir1 dir2 | ydiff  # view diff between two dirs

# View diff in a GitHub pull request, side by side
curl | ydiff -s

# View a patch file in unified format.
ydiff -s < foo.patch

Redirect output to another patch file is safe:

svn diff -r PREV | ydiff -s > my.patch

Environment variable

Environment variable YDIFF_OPTIONS may be used to specify default options that will be placed at the beginning of the argument list, for example:

export YDIFF_OPTIONS='-s -w0 --wrap'
ydiff foo                   # equivalent to "ydiff -s -w0 --wrap foo"

Note the default pager less takes options from the environment variable LESS.


If you feel more comfortable with a command such as git ydiff to trigger the ydiff command, you may symlink the executable to one named git-ydiff as follows:

ydiff_dir=$(dirname $(which ydiff))
ln -s "${ydiff_dir}/ydiff" "${ydiff_dir}/git-ydiff"

Known issues

Ydiff has following known issues:

  • Side by side mode has alignment problem for wide chars

  • Terminal might be in a mess on exception (type reset can fix it)

Pull requests are very welcome, please make sure your changes can pass unit tests and regression tests by run make docker-test.

Change log

Version 1.3 (2024-04-02)

  • Dropped context diff support

  • Handle East Asian wide characters (thanks to @roy2220)

  • Fix SIGPIPE issue on Windows (unofficial support, thanks to @kingsamchen)

  • Bump Python requirement to >=2.6 (Python 2 support is no longer tested)

Version 1.2 (2020-08-08)

  • Support perforce workspaces

  • Support pager customization via –pager and –pager_options

  • Support running on Windows (requires less which is offered by git-bash)

  • Fix a bug where reading stdin does not work outside a CVS workspace

  • Fix tab expansion, expands to the next stop modulo tab width

  • Performance improvement

Version 1.1 (2018-06-05)

  • Rename from cdiff to ydiff to avoid binary name conflict on major distributions, CDIFF_OPTIONS still works but will be deprepated soon

  • New option --wrap to wrap long lines in side-by-side view

Version 1.0 (2016-12-31)

  • Use environment variable CDIFF_OPTIONS to hold default options

Version 0.9.8 (2016-01-16)

  • More robust parser to tolerate evil unified diff

Version 0.9.7 (2015-04-24)

  • Fix unexpected side-by-side output for diff of diff

  • Better color to work with solarized color scheme

Version 0.9.6 (2014-06-20)

  • Fix TypeError exception in auto width logic

Version 0.9.5 (2014-06-19)

  • Option --width 0 now fits terminal size automatically

  • Enable smooth horizontal scrolling with less option --shift 1

Version 0.9.4 (2014-06-04)

  • Respect the LESS environment variable

  • Support python 3.4

  • Fix curl options in document

Version 0.9.3 (2013-09-28)

  • Moved screenshots to ‘gh-pages’ branch

  • Handle all keyboard interrupts more completely

  • Explicitly set default encoding to utf-8

  • Fixed broken output diff when I/O with filterdiff in nonblocking mode

Version 0.9.2 (2013-06-21)

  • Enahanced option parser now pass unknown option to underneath revision control, user can use cdiff --cached, cdiff -U5 directly

Version 0.9.1 (2013-05-20)

  • Use --no-ext-diff to disable GIT_EXTERNAL_DIFF and diff.external which might break cdiff output

Version 0.9 (2013-03-23)

  • Supports reading context diff via filterdiff (patchutils)

  • Fixed a diff parser bug which misread git commit message as common line

  • Lots of code refactor

Version 0.8 (2013-03-13)

  • Parser is now robust enough to handle dangling headers and short patch

  • PEP8 (with minor own flavors) and other code lint

  • Change ‘Development Status’ to stable

Version 0.7.1 (2013-02-25)

  • Handle ‘Binary files … differ’

  • Document update for known issues

Version 0.7 (2013-02-23)

  • Support reading diff or log for given files/dirs in workspace

  • Support diff generated from diff -ru dir1 dir2

  • Usage change: reading a patch and comparing two files need stdin redirect

Version 0.6 (2013-02-20)

  • A few performance tuning and code clean up

  • Add unit test cases with coverage 70%

  • Show merge history in svn log

Version 0.5.1 (2013-02-19)

  • Fixed incorrect yield on diff missing eof

  • Fixed a bug in diff format probe

  • Handle keyboard interrupt and large diffs in non-color mode

  • Code clean up

Version 0.5 (2013-02-18)

  • Support read output from svn diff --log and hg log -p

  • Streamline reading large patch set

  • New --log (-l) option to read revision control diff log (thanks to Steven Myint)

Version 0.4 (2013-02-16)

  • New option -c WHEN (–color WHEN) to support auto test

  • Auto regression test now on Travis

Version 0.3 (2013-02-07)

  • Support compare two files (wrapper of diff)

Version 0.2 (2013-02-06)

  • Move to top dir for better meta info management

Version 0.1 (2013-02-05)

  • New –version option

  • now read version from source code

Version 0.0.4 (2013-02-04)

  • Add CHANGES for history track and better versioning

Version 0.0.3 (2013-02-04)

  • Publish on PyPI, supports read patch from file, pipe and diff output from revision tools (thanks to Steven Myint)

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