Command-line reference

Synopsis

# compare two files or two folders (text / hex / folder is detected)
DiffScope.exe <left> <right> [options]
DiffScope.exe /base:<left> /mine:<right>              # TortoiseMerge diff style
DiffScope.exe --left <left> --right <right>

# 3-way merge
DiffScope.exe /base:B /mine:M /theirs:T /merged:OUT
DiffScope.exe --merge --base B --mine M --theirs T -o OUT
DiffScope.exe --merge <base> <mine> <theirs> [-o OUT]
DiffScope.exe <mine> <theirs> <base> <merged>          # Beyond Compare order

# no window: unified diff / merge result, exit codes 0, 1, 2
DiffScope.exe --headless <left> <right> > out.diff
DiffScope.exe --headless --merge B M T -o OUT

With no arguments, DiffScope opens the home screen. DiffScope.exe --help prints the built-in summary.

Syntax rules

Slash switches

Slash switches take their value after : or =, for example /base:file.txt or /title1="My file". Keywords are not case-sensitive.

The keywords are:

base mine theirs merged savetarget left right basename minename theirsname mergedname lefttitle righttitle centertitle outputtitle title1 title2 title3 title4 readonly ro leftreadonly rightreadonly automerge reviewconflicts help ?

• Values may be wrapped in double quotes; one pair of surrounding quotes is removed.
• A switch that needs a value but has none (/base) is an error. So is a value on a flag (/readonly:yes).
• An argument that is exactly a keyword (/ro) is always a switch. To pass a file with that name, put it after -- or write .\ro.

GNU options

• Long options take values as --base file or --base=file. Long option names are not case-sensitive.
• Short flags can be grouped (-wiB), and short values can be attached (-U5, -oout.txt, -o=out.txt).
• An unknown option is an error, and DiffScope suggests the closest name (did you mean --ignore-case?).
• -- ends the options. Everything after it is a path, even -x.txt or /title1:x.

Windows and Git Bash paths

• Relative paths are resolved against the current folder.
• If a Git Bash style path such as /c/Users/me/a.txt does not exist as written, DiffScope converts it to C:\Users\me\a.txt.
• Do not end a quoted path with a backslash ("C:\dir\"): Windows reads \" as an escaped quote. Write "C:\dir".
• Reading from standard input (-) is not supported.

Positional forms

Positional paths cannot be mixed with named paths (/base, --mine and so on), and the same path cannot be given twice.

Switch reference

Paths

A merge starts when /theirs, /merged or --merge is present; it then needs all of base, mine and theirs. /left /right cannot be mixed with /base /mine /theirs.

Titles

An empty value (/title1:) gives an empty title. Titles also label the conflict markers and the --- / +++ lines of headless output.

Modes

Only one of --text, --hex and --folder can be given. Merges are always text, so --hex and --folder are rejected for a merge.

Comparison options

These options also set the matching toolbar controls when a text compare window opens.

Folder options

Read-only

Other

Headless mode

With --headless, DiffScope runs the comparison or merge without opening a window, prints the result and exits.

What it prints

Merged output keeps the encoding and line endings of the inputs. The output file is written through a temporary file, so a failed run never leaves a half-written result.

Exit codes

In the window, a merge exits with 0 only when it was saved with no conflicts left, otherwise 1. A two-way compare window exits with 0 when closed, or 2 if the comparison could not be opened. See Closing and exit codes.

Examples for scripts and CI

# Fail the build when generated files drift from what is committed
& "C:\Tools\DiffScope\DiffScope.exe" --headless -w expected\api.json generated\api.json | Out-File drift.diff
if ($LASTEXITCODE -eq 1) { Write-Error "api.json changed, see drift.diff"; exit 1 }
if ($LASTEXITCODE -ge 2) { Write-Error "comparison failed"; exit 2 }

# Compare two release folders by content, skipping build output
& "C:\Tools\DiffScope\DiffScope.exe" --headless --folder --exclude node_modules --exclude "*.pdb" release\2.3 release\2.4 | Out-File tree.txt

# Try a 3-way merge; keep the result only when it is clean
# (the pipe makes PowerShell wait for the GUI program and set $LASTEXITCODE)
& "C:\Tools\DiffScope\DiffScope.exe" --headless --merge --diff3 base.cs mine.cs theirs.cs -o merged.cs | Out-Null
switch ($LASTEXITCODE) {
  0 { "merged cleanly" }
  1 { "conflicts left in merged.cs" }
  default { "merge failed" }
}

rem Unified diff with 5 lines of context, ignoring case and blank lines
"C:\Tools\DiffScope\DiffScope.exe" --headless -U5 -iB old.txt new.txt > changes.diff
echo Exit code %ERRORLEVEL%

# Paths starting with "-" go after --
"/c/Tools/DiffScope/DiffScope.exe" --headless -- -old.txt -new.txt | cat; echo "exit ${PIPESTATUS[0]}"

With cmd the console waits for the GUI program only inside a batch file or with start /wait. In an interactive prompt, use start /wait "" "C:\Tools\DiffScope\DiffScope.exe" … before reading %ERRORLEVEL%.