sdif - side-by-side diff viewer for ANSI terminal


sdif file_1 file_2

diff ... | sdif

    -i, --ignore-case
    -b, --ignore-space-change
    -w, --ignore-all-space
    -B, --ignore-blank-lines

    --[no]number, -n    print line number
    --digit=#           set the line number digits (default 4)
    --truncate, -t      truncate long line
    --[no]onword        fold line on word boundaries
    --context, -c, -C#  context diff
    --unified, -u, -U#  unified diff

    --width=#, -W#      specify width of output (default 80)
    --margin=#          specify margin column number (default 0)
    --mark=position     mark position (right, left, center, side) or no
    --column=order      set column order (default ONM)
    --view, -v          viewer mode
    --ambiguous=s       ambiguous character width (detect, wide, narrow)
    --[no]prefix        process git --graph output (default on)
    --prefix-pattern    prefix pattern

    --color=when        'always' (default), 'never' or 'auto'
    --nocolor           --color=never
    --colormap, --cm    specify color map
    --colortable        show color table
    --[no]256           on/off ANSI 256 color mode (default on)

    --man               display manual page
    --diff=s            set diff command
    --diffopts=s        set diff command options

    --[no]lenience      supress unexpected input warning (default on)

    --[no]cdif          use ``cdif'' as word context diff backend
    --unit=s            pass through to cdif
    --cdifopts=s        set cdif command options


sdif is inspired by System V sdiff(1) command. The basic feature of sdif is making a side-by-side listing of two different files. All contents of two files are listed on left and right sides. Center column is used to indicate how different those lines are. No mark means no difference. Added, deleted and modified lines are marked with minus (`-') and plus (`+') character, and wrapped line is marked with period (`.').

    1 deleted  -
    2 same          1 same
    3 changed  -+   2 modified
      wrapped  ..     folded
    4 same          3 same
                +   4 added

It also reads and formats the output from diff command from standard input. Besides normal diff output, context diff -c and unified diff -u output will be handled properly. Combined diff format is also supported, but currently limited up to three files.


sdif utilizes Perl Getopt::EX module, and reads ~/.sdifrc file if available when starting up. You can define original and default option there. To show the line number always, define like this:

    option default -n

Modules under App::sdif can be loaded by -M option without prefix. Next command load App::sdif::colors module.

    $ sdif -Mcolors

You can also define options in module file. Read `perldoc Getopt::EX::Module` for detail.


Each lines are displayed in different colors by default. Use --no-color option to disable it. Each text segment has own labels, and color for them can be specified by --colormap option. Read `perldoc Getopt::EX::Colormap` for detail.

Standard module -Mcolors is loaded by default, and define several color maps for light and dark screen. If you want to use CMY colors in dark screen, place next line in your ~/.sdifrc.

    option default --dark-cmy

Option --autocolor is defined in default module to call Getopt::EX::termcolor module. It sets --light or --dark option according to the brightness of the terminal screen. You can set preferred color in your ~/.sdifrc like:

    option --light --cmy
    option --dark  --dark-cmy

Automatic setting is done by Getopt::EX::termcolor module and it works with macOS and, and other XTerm compatible terminals. This module accept environment variable TERM_BGCOLOR as a terminal background color in a form of #FFFFFF.

Option --autocolor is set by default, so override it to do nothing to disable.

    option --autocolor --nop


While sdif doesn't care about the contents of each modified lines, it can read the output from cdif command which show the word context differences of each lines. Option --cdif set the appropriate options for cdif. Set --no-cc, --no-mc options at least when invoking cdif manually. Option --no-tc is preferable because text color can be handled by sdif.

From version 4.1.0, option --cdif is set by default, so use --no-cdif option to disable it. Option --unit (default word) will be passed through to cdif. Other cdif options can be specified by --cdifopts.


--width=width, -W width

Use width as a width of output listing. Default width is 80. If the standard error is assigned to a terminal, the width is taken from it if possible.


Set margin column number. Margin columns are left blank at the end of each line. This option implicitly declare line break control, which allows to run-in and run-out prohibited characters at the head-and-end of line. Margin columns are used to run-in prohibited characters from the head of next line. See `perldoc Text::ANSI::Fold` for detail.

--[no]number, -n

Print line number on each lines. Default false.


Print diff command control lines. Default true.


Line number is displayed in 4 digits by default. Use this option to change it.

-i, --ignore-case
-b, --ignore-space-change
-w, --ignore-all-space
-B, --ignore-blank-lines
-c, -Cn, -u, -Un

Passed through to the back-end diff command. Sdif can interpret the output from normal, context (diff -c) and unified diff (diff -u).

--[no]truncate, -t

Truncate lines if they are longer than printing width. Default false.


Fold long line at word boundaries. Default true.


Use cdif command instead of normal diff command. Enabled by default and use --no-cdif option explicitly to disable it. This option accepts optional parameter as an actual cdif command.


Specify options for back-end cdif command.


These options are simply sent to back-end cdif command. Default is --unit=word and char and mecab can be used. Option --mecab is same as --unit=mecab. Use --cdifopts to set other options.


Any command can be specified as a diff command to be used. Piping output to sdif is easier unless you want to get whole text.


Specify options for back-end diff command.


Specify the position for a mark. Choose from left, right, center, side or no. Default is center.


Specify the order of each column by O (1: old), N (2: new) and M (3: merge). Default order is "ONM" or "123". If you want to show new file on left side and old file in right side, use like:

    $ sdif --column NO

Next example show merged file on left-most column for diff3 data.

    $ sdif --column MON

Next two commands produce same output.

    $ git diff v1 v2 v3 | sdif --column 312

    $ git diff v3 v1 v2 | sdif

Use ANSI color escape sequence for output. Default is true.


Use ANSI 256 color mode. Default is true.


Show table of ANSI 216 colors.

--view, -v

Viewer mode. Display each files in straightforward order. Without this option, unchanged lines are placed at the same position.


This is an experimental option to specify how to treat Unicode ambiguous width characters. Default value is 'narrow'.

detect or auto

Detect from user's locate. Set 'wide' when used in CJK environment.

wide or full

Treat ambiguous characters as wide.

narrow or half

Treat ambiguous characters as narrow.


Understand prefix for diff output including git --graph option. True by default.


Specify prefix pattern in regex. Default pattern is:

    (?:\| )*(?:  )?

This pattern matches git graph style and whitespace indented diff output.


Supress warning message for unexpected input from diff command. True by default.

--colormap=colormap, --cm=colormap

Basic colormap format is :


where the FIELD is one from these :

    OLD       NEW       MERGED    UNCHANGED
    --------- --------- --------- ---------
    OCOMMAND  NCOMMAND  MCOMMAND           : Command line
    OFILE     NFILE     MFILE              : File name
    OMARK     NMARK     MMARK     UMARK    : Mark
    OLINE     NLINE     MLINE     ULINE    : Line number
    OTEXT     NTEXT     MTEXT     UTEXT    : Text

If UMARK and/or ULINE is empty, OMARK/NMARK and/or OLINE/NLINE are used instead.

You can make multiple fields same color joining them by = :


Also wildcard can be used for field name :


Multiple fields can be specified by repeating options

    --cm FILED1=COLOR1 --cm FIELD2=COLOR2 ...

or combined with comma (,) :

    --cm FILED1=COLOR1,FIELD2=COLOR2, ...

Color specification is a combination of single uppercase character representing 8 colors :

    R  Red
    G  Green
    B  Blue
    C  Cyan
    M  Magenta
    Y  Yellow
    K  Black
    W  White

and alternative (usually brighter) colors in lowercase :

    r, g, b, c, m, y, k, w

or RGB values and 24 grey levels if using ANSI 256 or full color terminal :

    (255,255,255)      : 24bit decimal RGB colors
    #000000 .. #FFFFFF : 24bit hex RGB colors
    #000    .. #FFF    : 12bit hex RGB 4096 colors
    000 .. 555         : 6x6x6 RGB 216 colors
    L00 .. L25         : Black (L00), 24 grey levels, White (L25)

or color names enclosed by angle bracket :

    <red> <blue> <green> <cyan> <magenta> <yellow>
    <aliceblue> <honeydue> <hotpink> <mooccasin>

with other special effects :

    D  Double-struck (boldface)
    I  Italic
    U  Underline
    S  Stand-out (reverse video)

Above color spec is simplified summary so if you want complete information, read Getopt::EX::Colormap.

Defaults are :

    OCOMMAND => "555/010"  or "GS"
    NCOMMAND => "555/010"  or "GS"
    MCOMMAND => "555/010"  or "GS"
    OFILE    => "551/010D" or "GDS"
    NFILE    => "551/010D" or "GDS"
    MFILE    => "551/010D" or "GDS"
    OMARK    => "010/444"  or "G/W"
    NMARK    => "010/444"  or "G/W"
    MMARK    => "010/444"  or "G/W"
    UMARK    => ""
    OLINE    => "220"      or "Y"
    NLINE    => "220"      or "Y"
    MLINE    => "220"      or "Y"
    ULINE    => ""
    OTEXT    => "K/454"    or "G"
    NTEXT    => "K/454"    or "G"
    MTEXT    => "K/454"    or "G"
    UTEXT    => ""

This is equivalent to :

    sdif --cm '?COMMAND=555/010,?FILE=555/010D' \
         --cm '?MARK=010/444,UMARK=' \
         --cm '?LINE=220,ULINE=' \
         --cm '?TEXT=K/454,UTEXT='



  default      --autocolor
  --nop        do nothing


Following options are available by default. Use `perldoc -m App::sdif::colors` to see actual setting.




Environment variable SDIFOPTS is used to set default options.


Kazumasa Utashiro


Copyright 1992-2020 Kazumasa Utashiro

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


cdif(1), watchdiff(1)