Shrink is a command for concatenating and compressing css stylesheets and javascript files making them smaller. Shrinking (or minifying) these files reduces the number of request that are made after a page load and also the size of these requests.

This command depends on YUI Compressor to do the work, and can be run with Python 2.5 and above (Python 3 not supported yet).


Shrink can be easily installed from pypi by running:

$ pip install shrink

After install is good to display script information and options:

$ shrink -h

Config file

INI style files are used to know which files will be minified, set some global options and also to know which files will be joined before minimization.

A good starting point to get familiar with Shrink config file format is to read the example shrink config file. To create an example file run:

$ shrink --example-cfg

This command creates a file called example_shrink.cfg in current folder.

Config file format

Config file has a section for each individual file that can be generated, and on top it also has a special section called DEFAULT where global options are defined.

Global DEFAULT options:
  • base_dir defines a base directory used as prefix to find static files. This value can be referenced in any other section using the python variable notation %(base_dir)s.
  • hash_dir defines a folder where shrink.sha1 file is stored. See Shrink hash file for more info. By default, this file is stored in the same folder where shrink config file is located.
  • arg.* defines default values for some command line argumens. Supported arguments are arg.java_bin and arg.yui_jar. The values given here are overriden by the ones given during runtime as command line arguments.

Each file section has some options that are used during join, compression and hashing of a file. These file section options are:

  • source_directory value defines the folder where file(s) listed in source_files are located.
  • source_files value can be a single file name, or a list of file names. When a list of names is given, each file in list is concatenated (from top to down) into a single file before compression.
  • destination_directory value sets output directory for the minified file By default minified file is generated in source directory.
  • destination_file value is the name for the minified file.
  • hash is a boolean value. When it is true destination file is included during shrink hash generation. See Shrink hash file.
  • compress is a boolean value. Destination file is not compressed when this value is false. By default compression is done for destination files. This option is useful when is desirable to join many files without compressing them because they are already compressed.

For example, a section for minifying a file called sample-file.js could be written as:

source_directory = %(base_dir)s/js
destination_file = sample-file.min.js
source_files = sample-file.js

Final minified file name would be sample-file.min.js.

Many files can also be specified to be joined into a single file before compression by writing a section like:

source_directory = %(base_dir)s/css
destination_file = sample-multiple-file.min.css
source_files =

Generated file name is given by destination_file value.

Minimize css and js files

To minimize all files, run:

$ shrink -f example_shrink.cfg all

This will use yuicompressor.jar and the example_shrink.cfg file in current directory to compress all files.

In case that minimzation is not desired for all files, is also possible to minimize individual files, or a group of files (See Section groups), by using the name(s) of each section instead of all as argument.

To list available sections, run:

$ shrink -f example_shrink.cfg -l

Section groups

Instead of running script with sample-single-file-js and sample-multiple-file-css as arguments is possible to define a group like:

group =

And then run minifier script with sample-group as the only parameter.

Shrink hash file

After minification Shrink can create a file containing a SHA1 hash. The file is created when at least one section in config file has hash = true. Hash is created using the contents of all destination files in these sections.

This is useful to know when some files changed, and to reload static css and javascript files without using a timestamp or version number. Sometime can be desirable to reload modified static files without increasing application version. In these cases the hash can be used as request parameter instead of version number.