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subst

subst version subst license subst python compatibility say thanks!

subst is simple utility to replace one string (or expression) into another in given list of files.

If you like this tool, just say thanks.

Current stable version

0.4.0

But why?

  1. There is sed for example?

    Yes, it is. But sed use regexps engine called "Basic Regular Expressions", or "Extended Regular Expression". PCRE (Perl Compatible Regular Expressions) used by subst is much more widely used engine.

  2. So I can use Perl!

    Of course you can. But not everyone know how to use Perl. I know, but subst is IMHO simpler to use.

OK, so how to use it?

Simple usage

echo 'Hello World!' | subst -s 's/Hello/Hi/' -

or:

subst -p '(192\.168)\.1\.(10)' -r '\1.0.\2' /etc/hosts

More

Everything is in help :) Just execute:

subst --help

Look at result:

% subst --help
usage: subst.py [-h] [-p PATTERN] [-r REPLACE] [--eval-replace] [-t]
                [-s "s/PAT/REP/gixsm"] [-c COUNT] [-l] [-i]
                [--pattern-dot-all] [--pattern-verbose] [--pattern-multiline]
                [-u] [--encoding-input ENCODING_INPUT]
                [--encoding-file ENCODING_FILE]
                [--encoding-filesystem ENCODING_FILESYSTEM] [-b] [-e EXT] [-W]
                [--stdin] [--stdout] [-V] [--debug] [-v]
                [files [files ...]]

Replace PATTERN with REPLACE in many files.

positional arguments:
files                 files to parse

optional arguments:
-h, --help            show this help message and exit
-p PATTERN, --pattern PATTERN
                        pattern to replace for. Supersede --pattern-and-
                        replace. Required if --replace is specified.
-r REPLACE, --replace REPLACE
                        replacement. Supersede --pattern-and-replace. Required
                        if --pattern is specified.
--eval-replace        if specified, make eval data from --replace(should be
                        valid Python code). Ignored with --pattern-and-replace
                        argument.
-t, --string          if specified, treats --pattern as string, not as
                        regular expression. Ignored with --pattern-and-replace
                        argument.
-s "s/PAT/REP/gixsm", --pattern-and-replace "s/PAT/REP/gixsm", --pattern-and-replace "s/PAT/REP/gixsm"
                        pattern and replacement in one:
                        s/pattern/replace/g(pattern is always regular
                        expression, /g is optional and stands for --count=0,
                        /i == --ignore-case, /s == --pattern-dot-all, /m ==
                        --pattern-multiline).
-c COUNT, --count COUNT
                        make COUNT replacements for every file (0 makes
                        unlimited changes, default).
-l, --linear          apply pattern for every line separately. Without this
                        flag whole file is read into memory.
-i, --ignore-case     ignore case of characters when matching
--pattern-dot-all     with this flag, dot(.) character in pattern match also
                        new line character (see:
                        https://docs.python.org/3/library/re.html#re.DOTALL).
--pattern-verbose     with this flag pattern can be passed as verbose(see:
                        https://docs.python.org/3/library/re.html#re.VERBOSE).
--pattern-multiline   with this flag pattern can be passed as multiline(see:
                        https://docs.python.org/3/library/re.html#re.MULTILINE
                        ).
-u, --utf8            Use UTF-8 in --encoding-input, --encoding-file and
                        --encoding-filesystem
--encoding-input ENCODING_INPUT
                        set encoding for parameters like --pattern etc
                        (default for your system: utf-8)
--encoding-file ENCODING_FILE
                        set encoding for content of processed files (default
                        for your system: utf-8)
--encoding-filesystem ENCODING_FILESYSTEM
                        set encoding for paths and filenames (default for your
                        system: utf-8)
-b, --no-backup       don't create backup of modified files.
-e EXT, --backup-extension EXT
                        extension for backup files(ignore if no backup is
                        created), without leading dot. Defaults to: "bak".
-W, --expand-wildcards
                        expand wildcards (see:
                        https://docs.python.org/3/library/glob.html) in paths
--stdin               read data from STDIN(implies --stdout)
--stdout              output data to STDOUT instead of change files in-
                        place(implies --no-backup)
-V, --verbose         show files and how many replacements was done and
                        short summary
--debug               show more informations
-v, --version         show program's version number and exit

Miscellaneous notes:
* regular expressions engine used here is PCRE, dialect from Python
* is required to pass either --pattern and -replace, or --pattern-and-
replace argument
* if pattern passed to --pattern-and-replace has /g modifier, it
overwrites --count value
* if neither /g modifier nor --count argument is passed, assume that
--count is equal 1
* if only --count is given, this value is used
* if --eval-replace is given, --replace must be valid Python code, where
can be used m variable. m holds MatchObject instance (see:
https://docs.python.org/3/library/re.html#match-objects, for example:
    --eval-replace --replace 'm.group(1).lower()'
* regular expressions with non linear search read whole file to yours
computer memory - if file size is bigger then you have memory in your
computer, it fails
* parsing expression passed to --pattern-and-replace argument is very
simple - if you use / as delimiter, then in your expression can't be
used this character anymore. If you need to use same character as
delimiter and in expression, then better use --pattern and --replace
arguments
* you can test exit code to verify there was made any changes (exit code
= 0) or not (exit code = 1)

Security notes:
* be careful with --eval-replace argument. When it's given, value passed
to --replace is eval-ed, so any unsafe code will be executed!

Author:
Marcin Sztolcman <marcin@urzenia.net> // http://urzenia.net

HomePage:
http://msztolcman.github.io/subst/

More examples?

Simple replace word 'Hello' with 'Hi' in data read from STDIN:

echo 'Hello World!' | subst -s 's/Hello/Hi/' -

Replace every IP address in form: 192.168.1.X (where X is few digits - single octet) with 192.168.0.X in /etc/hosts:

subst -p '(192\.168)\.1\.(10)' -r '\1.0.\2' /etc/hosts

Regular expressions

A.K.A. regex or regexp. You can read more on Wikipedia. Other resources:

Installation

subst should work on any platform where Python is available, it means Linux, Windows, MacOS X etc. There is no dependencies, plain Python power :)

  1. Installtion using PIP

Simplest way is to use Python's built-in package system:

pip install subst
  1. Using sources

To install, go to GitHub releases, download newest release, unpack and put somewhere in PATH (ie. ~/bin or /usr/local/bin).

If You want to install newest unstable version, then just copy file to your PATH, for example:

curl https://raw.github.com/msztolcman/subst/master/subst.py > /usr/local/bin/subst

or:

wget https://raw.github.com/msztolcman/subst/master/subst.py -O /usr/local/bin/subst

Voila!

Python compatibility

subst is tested against Python 2.7 and Python 3.3+

Authors

Marcin Sztolcman marcin@urzenia.net

Contact

If you like or dislike this software, please do not hesitate to tell me about this me via email (marcin@urzenia.net).

If you find bug or have an idea to enhance this tool, please use GitHub's issues.

License

The MIT License (MIT)

Copyright (c) 2013 Marcin Sztolcman

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

ChangeLog

(dev)

  • dropped compatibility with Python 2.6
  • paths are now normalized before processing
  • improvements to handling different encodings
  • exit code give us info about there was any changes
  • added switch --expand-wildcards (-W)
  • added -V switch as an alias for --verbose
  • passing invalid flags to --pattern-and-replace is now an error
  • fixes and improvements in built-in help
  • --pattern-* and --ignore-case was ignored for --pattern and --replace parameters
  • --pattern-and-replace was incorrectly parsed with braces as delimiters
  • fixed bug with changing new-line characters from dos to unix (issue #5)
  • fixed bug with bad interpretation of -t param (issue #4)
  • fixed bug with using subst on Windows (issue #2)
  • using singular form in verbose mode when it's required
  • tests are now using py.test framework, also added many new tests
  • many refactorings
  • improvements to pylintrc, Makefile
  • using Pipenv to handling dependencies
  • config for tox
  • marked as compatible with Python 3.5 and 3.6

v0.4.0

  • PEP8 improvements (coding style)
  • Makefile added
  • improved pylintrc

v0.3.1

  • prepared and uploaded to PYPI
  • typos and editorials

v0.3

  • better handling of non-ascii encoding in files, patterns etc
  • higher priority for --pattern-* switches then modifiers in --pattern-and-replace
  • unified switches syntax (was --pattern_and_replace, but other switches used dashes)
  • pep8
  • typos and editorials

v0.2

  • second public version