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When I run setuptools.egg "as if it is a shell script", what actually happens?

After reading this documentation , I created a mental model of what the sh setuptools-0.6c11-py2.7.egg , but it’s very incomplete, and I’m still puzzled by several aspects.

My mental model looks something like this:

  • When this command is issued, the egg (which I saw as a kind of zip file that skillfully handles dependencies) somehow finds the correct version of python on my system, and using this python "sets itself" to a suitable location.
  • In practice, this means that the “Unix Executable File,” called easy_install, is created in a directory that I hope is in my way. That is why I can simply enter easy_install somepackage into the terminal after this.

So my questions are:

  • How can an “egg” establish itself in this way? Why does this work for this egg, in particular when other eggs require easy_install to work?
  • Thus created "Unix executable" is 4kb. What really Is he full of calls to other things? Where are they?

It is not a question of how to make it work. I have no problems on this axis, but I would like to fully understand what is happening here.

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Egg files are simply zip-compressed directories containing Python packages, modules, and small metadata with the .egg extension.

The zip format is flexible; it will ignore anything at the beginning of the file that is not part of the zip file. A zip file is detected by searching for a series of characters ( PK and two more bytes indicating the type) and reading from there.

This means that you can put something in front of the zip code. Setuptools eggs are different in that they use this trick to insert some shell script before the zip data:

 $ head -n8 setuptools-0.6c11-py2.7.egg #!/bin/sh if [ `basename $0` = "setuptools-0.6c11-py2.7.egg" ] then exec python2.7 -c "import sys, os; sys.path.insert(0, os.path.abspath('$0')); from setuptools.command.easy_install import bootstrap; sys.exit(bootstrap())" " $@ " else echo $0 is not the correct name for this egg file. echo Please rename it back to setuptools-0.6c11-py2.7.egg and try again. exec false fi

Past the first 8 lines, this is a genuine zip:

 $ tail -n+9 setuptools-0.6c11-py2.7.egg | file - /dev/stdin: Zip archive data, at least v2.0 to extract

The script contained in these first 8 lines is what is executed when sh setuptools-0.6c11-py2.7.egg .

As you can see, the script depends on the version of the egg; this is in the version for python 2.7, and it just uses the python interpreter to add this egg to the python search path. Then it imports the function from the python module it contains and runs it.

Here is the contents of the egg itself, which, as I mentioned, is just a zip archive:

 $ zipinfo -l setuptools-0.6c11-py2.7.egg Archive: setuptools-0.6c11-py2.7.egg 332005 bytes 78 files -rw-rw-r-- 2.0 unx 1713 b- 995 defN 7-Jul-10 20:26 site.pyc -rw-rw-r-- 2.0 unx 90113 b- 31461 defN 7-Jul-10 20:26 pkg_resources.pyc -rw-rw-r-- 2.0 unx 85435 b- 23537 defN 19-Oct-09 13:35 pkg_resources.py -rw-rw-r-- 2.0 unx 2362 b- 875 defN 20-Sep-06 17:05 site.py -rw-rw-r-- 2.0 unx 309 b- 224 defN 7-Jul-10 20:26 easy_install.pyc -rw-rw-r-- 2.0 unx 126 b- 105 defN 20-Sep-06 17:05 easy_install.py -rw-rw-r-- 2.0 unx 43 b- 43 defN 7-Jul-10 20:26 EGG-INFO/top_level.txt -rw-rw-r-- 2.0 unx 1591 b- 458 defN 7-Jul-10 20:26 EGG-INFO/SOURCES.txt -rw-rw-r-- 2.0 unx 1 b- 3 defN 20-Oct-09 10:07 EGG-INFO/zip-safe -rw-rw-r-- 2.0 unx 9278 b- 3194 defN 7-Jul-10 20:26 EGG-INFO/PKG-INFO -rwxrwxr-x 2.0 unx 2504 b- 623 defN 7-Jul-10 20:26 EGG-INFO/entry_points.txt -rw-rw-r-- 2.0 unx 1 b- 3 defN 7-Jul-10 20:26 EGG-INFO/dependency_links.txt -rw-rw-r-- 2.0 unx 1567 b- 791 defN 7-Jul-10 20:26 setuptools/extension.pyc -rw-rw-r-- 2.0 unx 1089 b- 424 defN 20-Sep-06 17:05 setuptools/extension.py -rw-rw-r-- 2.0 unx 10796 b- 4050 defN 7-Jul-10 20:26 setuptools/sandbox.pyc -rw-rw-r-- 2.0 unx 8227 b- 2309 defN 6-Jul-10 20:09 setuptools/sandbox.py -rw-rw-r-- 2.0 unx 5677 b- 2499 defN 7-Jul-10 20:26 setuptools/archive_util.pyc -rw-rw-r-- 2.0 unx 26800 b- 11228 defN 7-Jul-10 20:26 setuptools/package_index.pyc -rw-rw-r-- 2.0 unx 6209 b- 2229 defN 19-Oct-09 13:35 setuptools/depends.py -rw-rw-r-- 2.0 unx 6677 b- 3096 defN 7-Jul-10 20:26 setuptools/depends.pyc -rw-rw-r-- 2.0 unx 2816 b- 1159 defN 6-Jul-10 20:09 setuptools/__init__.py -rw-rw-r-- 2.0 unx 3639 b- 1837 defN 7-Jul-10 20:26 setuptools/__init__.pyc -rw-rw-r-- 2.0 unx 5924 b- 1777 defN 19-Oct-09 13:35 setuptools/archive_util.py -rw-rw-r-- 2.0 unx 29972 b- 8156 defN 19-Oct-09 13:35 setuptools/dist.py -rwxrwxr-x 2.0 unx 7168 b- 3249 defN 19-Oct-09 17:18 setuptools/cli.exe -rw-rw-r-- 2.0 unx 28275 b- 8698 defN 6-Jul-10 20:09 setuptools/package_index.py -rw-rw-r-- 2.0 unx 29786 b- 10953 defN 7-Jul-10 20:26 setuptools/dist.pyc -rwxrwxr-x 2.0 unx 7168 b- 3244 defN 19-Oct-09 17:18 setuptools/gui.exe -rw-rw-r-- 2.0 unx 22219 b- 7042 defN 7-Jul-10 20:26 setuptools/tests/test_resources.pyc -rw-rw-r-- 2.0 unx 19388 b- 4723 defN 24-Sep-08 13:10 setuptools/tests/test_resources.py -rw-rw-r-- 2.0 unx 12345 b- 2765 defN 24-Sep-08 13:10 setuptools/tests/__init__.py -rw-rw-r-- 2.0 unx 13811 b- 4523 defN 7-Jul-10 20:26 setuptools/tests/__init__.pyc -rw-rw-r-- 2.0 unx 1499 b- 708 defN 7-Jul-10 20:26 setuptools/tests/test_packageindex.pyc -rw-rw-r-- 2.0 unx 81351 b- 27171 defN 7-Jul-10 20:26 setuptools/tests/doctest.pyc -rw-rw-r-- 2.0 unx 759 b- 346 defN 24-Sep-08 13:10 setuptools/tests/test_packageindex.py -rw-rw-r-- 2.0 unx 99714 b- 25663 defN 20-Sep-06 17:05 setuptools/tests/doctest.py -rw-rw-r-- 2.0 unx 2866 b- 1332 defN 7-Jul-10 20:26 setuptools/command/rotate.pyc -rw-rw-r-- 2.0 unx 11520 b- 3127 defN 19-Oct-09 13:35 setuptools/command/build_ext.py -rw-rw-r-- 2.0 unx 6649 b- 2208 defN 24-Sep-08 13:10 setuptools/command/upload.py -rw-rw-r-- 2.0 unx 8162 b- 3538 defN 7-Jul-10 20:26 setuptools/command/sdist.pyc -rw-rw-r-- 2.0 unx 5965 b- 2421 defN 7-Jul-10 20:26 setuptools/command/setopt.pyc -rw-rw-r-- 2.0 unx 2283 b- 695 defN 19-Oct-09 17:50 setuptools/command/bdist_wininst.py -rw-rw-r-- 2.0 unx 7535 b- 3208 defN 7-Jul-10 20:26 setuptools/command/build_py.pyc -rw-rw-r-- 2.0 unx 3690 b- 1528 defN 7-Jul-10 20:26 setuptools/command/install.pyc -rw-rw-r-- 2.0 unx 14205 b- 4465 defN 19-Oct-09 13:35 setuptools/command/egg_info.py -rw-rw-r-- 2.0 unx 626 b- 311 defN 28-Dec-06 19:52 setuptools/command/__init__.py -rw-rw-r-- 2.0 unx 839 b- 494 defN 7-Jul-10 20:26 setuptools/command/__init__.pyc -rw-rw-r-- 2.0 unx 5053 b- 1519 defN 20-Sep-06 17:05 setuptools/command/setopt.py -rw-rw-r-- 2.0 unx 674 b- 329 defN 7-Jul-10 20:26 setuptools/command/register.pyc -rw-rw-r-- 2.0 unx 3724 b- 1292 defN 4-Sep-07 00:11 setuptools/command/install_egg_info.py -rw-rw-r-- 2.0 unx 18005 b- 5444 defN 19-Oct-09 13:35 setuptools/command/bdist_egg.py -rw-rw-r-- 2.0 unx 3984 b- 1385 defN 15-Feb-08 12:29 setuptools/command/install.py -rw-rw-r-- 2.0 unx 2356 b- 1002 defN 7-Jul-10 20:26 setuptools/command/bdist_wininst.pyc -rw-rw-r-- 2.0 unx 2025 b- 774 defN 22-May-07 17:55 setuptools/command/bdist_rpm.py -rw-rw-r-- 2.0 unx 2486 b- 871 defN 20-Sep-06 17:05 setuptools/command/install_lib.py -rw-rw-r-- 2.0 unx 740 b- 357 defN 20-Sep-06 17:05 setuptools/command/saveopts.py -rw-rw-r-- 2.0 unx 56980 b- 23198 defN 7-Jul-10 20:26 setuptools/command/easy_install.pyc -rw-rw-r-- 2.0 unx 3172 b- 1438 defN 7-Jul-10 20:26 setuptools/command/install_lib.pyc -rw-rw-r-- 2.0 unx 2257 b- 1013 defN 7-Jul-10 20:26 setuptools/command/bdist_rpm.pyc -rw-rw-r-- 2.0 unx 5310 b- 1732 defN 15-Feb-08 12:29 setuptools/command/develop.py -rw-rw-r-- 2.0 unx 5091 b- 2222 defN 7-Jul-10 20:26 setuptools/command/test.pyc -rw-rw-r-- 2.0 unx 63580 b- 17507 defN 19-Oct-09 13:35 setuptools/command/easy_install.py -rw-rw-r-- 2.0 unx 16467 b- 6544 defN 7-Jul-10 20:26 setuptools/command/egg_info.pyc -rw-rw-r-- 2.0 unx 4577 b- 1994 defN 7-Jul-10 20:26 setuptools/command/install_egg_info.pyc -rw-rw-r-- 2.0 unx 6275 b- 3108 defN 7-Jul-10 20:26 setuptools/command/upload.pyc -rw-rw-r-- 2.0 unx 7246 b- 2237 defN 20-Sep-06 17:05 setuptools/command/build_py.py -rw-rw-r-- 2.0 unx 10073 b- 4314 defN 7-Jul-10 20:26 setuptools/command/build_ext.pyc -rw-rw-r-- 2.0 unx 3185 b- 1463 defN 7-Jul-10 20:26 setuptools/command/alias.pyc -rw-rw-r-- 2.0 unx 1921 b- 704 defN 15-Feb-08 12:29 setuptools/command/install_scripts.py -rw-rw-r-- 2.0 unx 7327 b- 2380 defN 19-Oct-09 15:46 setuptools/command/sdist.py -rw-rw-r-- 2.0 unx 1249 b- 647 defN 7-Jul-10 20:26 setuptools/command/saveopts.pyc -rw-rw-r-- 2.0 unx 2021 b- 750 defN 20-Sep-06 17:05 setuptools/command/rotate.py -rw-rw-r-- 2.0 unx 2477 b- 848 defN 19-Oct-09 13:35 setuptools/command/alias.py -rw-rw-r-- 2.0 unx 17695 b- 7800 defN 7-Jul-10 20:26 setuptools/command/bdist_egg.pyc -rw-rw-r-- 2.0 unx 277 b- 158 defN 20-Sep-06 17:05 setuptools/command/register.py -rw-rw-r-- 2.0 unx 4442 b- 1424 defN 15-Feb-08 12:29 setuptools/command/test.py -rw-rw-r-- 2.0 unx 2445 b- 1160 defN 7-Jul-10 20:26 setuptools/command/install_scripts.pyc -rw-rw-r-- 2.0 unx 5175 b- 2317 defN 7-Jul-10 20:26 setuptools/command/develop.pyc 78 files, 958981 bytes uncompressed, 321419 bytes compressed: 66.5%
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Source: https://habr.com/ru/post/1446248/

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