'dif' compares files after it preprocesses them.
Preprocessing options include:
- remove comments, whitespace, timestamps
- search/replace
- keep/ignore certain lines
- json/yaml reformatting
- parse values from xls spreadsheets
- many other options (see far below)
'dif' can also be used to compare directories recursively, after optionally preprocessing each file
The graphical compare tools meld, gvimdiff, kdiff3, tkdiff, and kompare are used to compare text files on Linux
In many cases, it is difficult and time-consuming to visually compare large files because of the large number of differences
For example:
- different versions of code may differ only in comments or whitespace
- log files are often many MB of text, with some "don't care" information such as timestamps or temporary filenames
- json or yaml files may have ordering differences due to the library used to write the file
- xls spreadsheets cannot be compared easily because of the file format
'dif' preprocesses input text files with a wide variety of options
Afterwards, it runs the Linux tools meld, gvimdiff, kdiff3, tkdiff, or kompare on these intermediate files
This allows you to concentrate on the important differences, and ignore the rest
Solution: Use options -white or -nowhite or -comments or -case
Solution 1: Use -grep or -ignore to filter in or out
Solution 2: Use -search -replace to supply one instance of substitution and replacement
Solution 3: Use -replaceTable to supply a file with many substitution/replacement regexes
Solution 4: Use -replaceDates to remove dates and timestamps
Solution: 'dif file' will show the differences between the head revision and the local file
Solution 1: 'dif dir1 dir2' will iteratively compare pairs of files
Solution 2: 'dif dir1 dir2 -report' will open a GUI to compare the directories
Any preprocessing option (-comments, -white, -sort, -grep, etc) can be used when comparing directories
- dif file1 file2
- dif file1 file2 -white -case
- dif file1 file2 file3 -comments
- dif file1 file2 -search 'foo' -replace 'bar'
- dif file1.xls file2.xls
- dif dir1 dir2 -report
Filtering options:
-comments Remove any comments such as // or # or single-line */ /*. Also removes trailing whitespace
To remove comments in other languages, use the search/replace options:
For example, to replace comments (marked with ';') in assembly language:
-search '\s*(;.*)?$' -replace ''
-white Remove blank lines and leading/trailing whitespace
Condense multiple whitespace to a single space
Remove any non-printable characters
-noWhite Remove all whitespace and non-printable characters
-case Convert files to lowercase before comparing
-grep 'regex' Only display lines which match the user-specified Perl regex
Multiple regexs can be specified, for example: -grep '(regexA|regexB)'
To display lines above/below matches, see the help text for option -externalPreprocessScript
-ignore 'regex' Ignore any lines which match the user-specified regex
This is the opposite of the -grep function
-search 'regex' On each line, do a global regex search and replace
-replace 'regex'
For example, to replace temporary filenames such as '/tmp/foo123456/bar.log' with '/tmp/file':
-search '/tmp/\S+' -replace '/tmp/file'
Since the search/replace terms are interpreted as regex,
remember to escape any parentheses
Exception: if you are using regex grouping,
do not escape the parentheses
For example:
-search '(A|B|C)' -replace 'D'
Since the replace term is run through 'eval', make sure to escape any $ dollar signs
Make sure to use 'single-quotes' instead of double-quotes
For example, to convert all spaces to newlines, use:
-search '\s+' -replace '\n'
If case-insensitive search is needed, also use option -case
-replaceTable file Specify a two-column file which will be used for search/replace
The delimiter is any amount of spaces
Terms in the file are treated as regular expressions
The replace term is run through eval
-replaceDates Remove dates and times, for example:
17:36:34
Monday July 20 17:36:34 PDT 2020
Dec 3 2019
Jul 10 17:42
1970.01.01
1/1/1970
-fields N Compare only field(s) N
Multiple fields may be given, separated by commas (-fields N,M)
Field numbers start at 0
Fields in the input files are assumed to be separated by spaces,
unless the filename ends with .csv (separated by commas)
Example: -fields 2
Example: -fields 0,2 (fields 0 and 2)
Example: -fields -1 (last field)
Example: -fields 2+ (field 2 and above)
Example: -fields not2+ (ignore fields 2 and above)
Example: -fields not0,5+ (ignore fields 0, 5, and above)
-fieldSeparator regex Only needed if default field separators above are not sufficient
Example: -fieldSeparator ':'
Example: -fieldSeparator '[,=]'
-fieldJustify Make all fields the same width, right-justified
-split Splits each line on whitespace
-splitChar 'char' Splits each line on 'char'
For example: -splitChar ',' to split on comma
-splitWords Splits on whitespace. Each word will be on its own line.
Identical to -splitChar '\s+'
-trim Trims each line to 105 characters, discarding the overflow
Useful when lines are very long, and the important information is near the beginning
-trimChars N Trims with specified number of characters, instead of 105
-head Compare only the first 10% of the file,
with a minimum of 50, and a maximum of 10000 lines
-headLines N Compare only the first N lines
If a negative number is used, ignore the first -N lines
-tail Compare only the last 10% of the file
with a minimum of 50, and a maximum of 10000 lines
-tailLines N Compare only the last N lines
If a negative number is used, ignore the last -N lines
-yaml Compare two yaml files, sorting the keys
-json Compare two json files, sorting the keys
-removeDictKeys 'regex'
For use with -yaml or -json
Removes all dictionary keys matching the regex
Removes all dictionary keys matching the regex
-flatten For use with -yaml or -json
Flatten nested dictionary and array structures
-basenames Convert path/file to file
This can be useful when comparing log files which contain temporary directories
-extensions Convert path/file.extension to .extension
-removeExtensions Convert path/file.extension to path/file
-lineWordSort Sort the words in each line (space delimited)
-round 'string' Round all numbers according to the sprintf string
For example -round '%0.2f'
-dos2unix Run all files through dos2unix
-lsl Useful when comparing previously captured output of 'ls -l'
Compares only names and file sizes
-tartv Compare tarfiles using tar -tv, and compare the names and file sizes
If file sizes are not desired in the comparison (names only), also use -fields 1
-perlEval The input file is a perl hashref
Print the keys in alphabetical order
-perlDump Useful when comparing previously captured output of Data::Dumper
filter out all SCALAR/HASH/ARRAY/REF/GLOB/CODE addresses from output of Dumpvalue,
since they change on every execution
'SPECS' => HASH(0x9880110) becomes 'SPECS' => HASH()
Also works on Python object dumps:
<_sre.SRE_Pattern object at 0x216e600>
Filtering options to target a section of the file:
-start 'regex' Start comparing file when line matches 'regex'
If multiple lines matching regexes should be required to start capturing,
Separate the regexes with ^^
For example, to start capture after line matching 'abc' and then line matching 'def':
-start 'abc^^def'
By default, only the first occurrence of the start/stop sequence will be captured,
if multiple occurrences exist within the file
-stop 'regex' Stop comparing file when line matches regex
The last matching line will be captured, unless specified otherwise
-startIgnoreFirstLine This modifies the 'start' operation, so that
The first matching line will not be captured
-stopIgnoreLastLine This modifies the 'stop' operation, so that
The last matching line will not be captured
-startMultiple This modifies the 'start' operation, so that
multiple occurrences of the same start/stop sequence may be captured
-start1 -stop1 -start2 -stop2
Similar to -start and -stop
The '1' and '2' refer the files
Enables comparing different sections within the same file,
or different sections within different files
For example, to compare functions 'add' and 'subtract' within a single file:
dif a.pm -start1 'sub add' -stop1 '^}' -start2 'sub subtract' -stop '^}'
-function 'function_name'
Compare same Python def / Perl sub / TCL proc / JavaScript function from two source files
Internally, this leverages the -start -stop functionality
This feature will also work for some C source files
-functionSort
Useful when Python/Perl/TCL/JavaScript functions have been moved within a file
This option preprocesses each file, so that the function definitions
appear in alphabetical order
This feature will also work for some C source files
-language <lang> For use with -function and -functionSort
The language is automatically determined by inspecting the file extension and shebang
Use this option if those clues are not present
Languages are specified as extensions such as: js pl py tcl
Preprocessing options (before filtering):
-externalPreprocessScript <script>
Run each input file through your custom preprocessing script
It must take input from STDIN and send output to STDOUT, similar to unix 'sort'
Trivial example:
-externalPreprocessScript 'sort'
Example using grep to show 2 lines above and below lines matching the regex 'foo'
-ext 'grep -C 2 foo'
Examples for comparing binary files:
-ext '/usr/bin/xxd'
-ext '/usr/bin/xxd -c1 -p'
-ext '/usr/bin/hexdump -c'
However, a standalone diff tool may be preferable for comparing binary files
For example:
'qdiff' by Johannes Overmann and Tong Sun
'colorbindiff' by Jerome Lelasseux
'VBinDiff' by Christopher J. Madsen
'dhex'
-bin Compare binary files
This is a shortcut for running -ext '/usr/bin/xxd'
-strings Run equivalent of Linux 'strings' command on each input file to remove binary characters
-bcpp Run each cpp input file through bcpp linting tool with options: /home/ckoknat/cs2/linux/bcpp -s -bcl -tbcl -ylcnc
-perltidy Run each Perl input file through perltidy linting tool with options: /home/utils/perl5/perlbrew/perls/5.26.2-060/bin/perltidy -l=110 -ce
Postprocessing options (after filtering):
-sort Run Linux 'sort' on each input file
-uniq Run Linux 'uniq' on each input file to eliminate duplicated adjacent lines
Use with -sort to eliminate all duplicates
-fold Run 'fold' on each input file with default of 105 characters per column
Useful for comparing long lines, so that scrolling right is not needed within the GUI
-foldChars N Run 'fold' on each input file with N characters per column
-ppOnly Stop after creating preprocessed files
Viewing options:
-quiet Do not print to screen
-verbose Print names and file sizes of preprocessed temporary files, before comparing
-gui cmd Instead of using kompare to graphically compare the files, use a different tool
This supports any tool which has command line usage similar to gvimdiff
i.e. 'gvimdiff file1 file2'.
This has been tested on meld, gvimdiff, kdiff3, tkdiff, and kompare, and likely works
with diffmerge, diffuse, kdiff, wdiff, xxdiff, colordiff, beyond compare, etc
Examples:
-gui gvimdiff
Uses gvimdiff as a GUI
-gui kdiff3
Uses kdiff3 as a GUI
-gui tkdiff
Uses tkdiff as a GUI
-gui kompare
Uses kompare as a GUI
-gui meld
Uses meld as a GUI
Note that meld does not display line numbers by default on some OS
Meld / Preferences / Editor / Display / Show line numbers
If the box is greyed out, install python-gtksourceview2
-gui opendiff
Use the macOS FileMerge tool (requires Xcode)
-gui none
This is useful when comparing from a script
in an automated process such as regression testing
After running dif, the return status will be:
0 = files are equal
1 = files are different
dif a.yml b.yml -gui none -quiet ; echo $?
-gui diff
Prints diff to stdout instead of to a GUI
-gui 'diff -C 1' | grep -v '^[*-]'
Use diff, with the options:
one line of Context above and below the diff
remove the line numbers of the diffs
-diff Shortcut for '-gui diff'
Options to compare a large set of files:
<dirA> <dirB> If dif is run against two directories,
will open GUI for each pair of mismatching files
For example:
dif dirA dirB
Any of the preprocessing options may be used
-report When used with two directories or -dir2 <dir> or -gold
Instead of opening GUIs for each file pair,
generate report of mismatching or missing files
For example:
dif dirA dirB -report
Any of the preprocessing options may be used
It can also be used to print a simple report of
file sizes, number of lines, and md5sums (not a comparison)
For example:
dif * -report
or
dif */file -report
or
dif dir -report
-filePairs Similar to -report, but only displays the files which are found in both directories, and mismatch
-filePairsWithOptions Similar to -filePairs, but also lists the dif command and options
-intersection When used with -report, only list files which exist in both directories
-fast When used with -report, use only the file size to compare, instead of md5sum
This is much faster, but could miss cases where bits are flipped
-includeFiles <regex>
-excludeFiles <regex> Both options are for use with two directories or -dir2 <dir> or -gold
For example:
dif -includeFiles '*log' dirA dirB
Will open GUI for each pair of mismatching files
When used with -dir2 or -gold,
finds files in the current directory matching the Perl regex
For example:
dif -includeFiles '*log' -dir2 ../old
Any of the preprocessing options may be used
-dir2 <dir> For each input file specified, run 'dif'
on the file in the current directory
against the file in the specified directory
For example:
cd to the directory containing the files
dif file1 file2 file3 -dir ../old
will run:
dif file1 ../old/file1
dif file2 ../old/file2
dif file3 ../old/file3
Any of the preprocessing options may be used
-gold When used with one filename (file or file.extension),
assumes that 1st file will be (file.golden or file.golden.extension)
For example:
dif file1 -gold
will run:
dif file1.golden file1.csv
For example:
dif file1.csv -gold
will run:
dif file1.csv.golden file1.csv
When used with multiple filenames
it runs dif multiple times, once for each of the pairs
This option is useful when doing regressions against golden files
For example:
dif file1 file2.csv -gold
will run:
dif file1.golden file1
dif file2.csv.golden file2.csv
Any of the preprocessing options may be used
-tree <dir1> <dir2> Special case. Run unix 'tree' on each of the directories. Does not preprocess files
Other options:
-stdin Parse input from stdin and send output to stdout
For example:
grep foo bar | dif -stdin <options> | script2 | script3
-stdout Cat all preprocessed files to stdout
In this use case, dif could be called on only one file
This allows dif to be part of a pipeline
For example:
dif file -stdout <options> | another_script
If -stdin is given, then -stdout is assumed
-out <file> Similar to -stdout, but send output to file
This can be useful if dif is used as a preprocessing engine
-filename Intended for use with option -stdout or -out
At the beginning of each line, prepend the filename
This is similar to the grep --with-filename option
Useful when searching through a large set of files
-keeptmp Default behavior is to remove the tmp directory containing preprocessed files
This option keeps it
Other features:
Automatically uncompresses files from these formats into intermediate files:
.gz
.bz2
.xz
.Z
.zip (single files only)
Compares values inside .xls|.xlsm|.xlsx files
requires the Perl Spreadsheet::BasicRead, Spreadsheet::ParseExcel, and Spreadsheet::XLSX modules to be installed
Compares values inside .ods OpenOffice spreadsheet files
requires the Perl Spreadsheet::Read and Spreadsheet::ParseODS module to be installed
Attempts to compare text inside .pdf files
requires the Perl CAM::PDF module to be installed
Default compare tool: The default compare GUI is meld To change this, create the text file ~/.dif.defaults with one of these content lines: gui: gvimdiff gui: tkdiff gui: kdiff3 gui: kompare gui: meld gui: tkdiff You may also want to change the default (uncompressed) file size limit, before gvimdiff takes over from kompare/meld The default is 2000000 bytes meldSizeLimit: 1000000
For convenience, link to this code from ~/bin
ln -s /path/dif ~/bin/dif
Perforce or SVN version control support:
Perforce uses '#' to signify version numbers. dif borrows the same notation for SVN
Perforce or SVN examples:
dif file compares head version with local version (shortcut)
dif file#h compares head version with local version (shortcut)
dif file file#head compares head version with local version
dif file#head #- compares head version with previous version (shortcut)
dif file#7 compares version 7 with local version (shortcut)
dif file#6 file#7 compares version 6 with version 7
dif file#6 file#+ compares version 6 with version 7
dif file#6 file#- compares version 6 with version 5
dif file#6..#9 compares version 6 with version 7, and then compares 7 with 8, then 8 with 9
Git example:
dif file compares committed version to local version
No installation is needed, just copy the 'dif' executable
To see usage:
- cd .. (back into dif main directory)
- ./dif
To run dif:
- ./dif file1 file2
To run the tests (optional):
- download dif from GitHub and uncompress it
- cd dif/test
- ./dif.t
This will run dif on the example* unit tests It should return with 'all tests passed'
Perl versions 5.6.1 through 5.30 have been tested
For convenience, copy the dif executable to your ~/bin directory, or create an alias:
alias dif /path/dif/dif
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