What is the function of this python script(python-exec tool)?

Question

Recently I happened a strange problem.

My OS is Gentoo. I install pip and layman, but the binary file in /usr/bin: /usr/bin/pip and /usr/bin/layman, are all softlink to /usr/bin/python-exec.

% ll /usr/bin/{pip,layman}
lrwxrwxrwx 1 root root 11 Sep 18 23:51 /usr/bin/layman -> python-exec
lrwxrwxrwx 1 root root 11 Aug 16 08:14 /usr/bin/pip -> python-exec

The content of /usr/bin/python-exec:

#!/usr/bin/python2.7
# EASY-INSTALL-ENTRY-SCRIPT: 'Pygments==1.6','console_scripts','pygmentize'
__requires__ = 'Pygments==1.6'
import sys
from pkg_resources import load_entry_point

sys.exit(
   load_entry_point('Pygments==1.6', 'console_scripts', 'pygmentize')()
) 

I found this file belongs to dev-python/python-exec-0.3.1:

% equery belongs python-exec
 * Searching for python-exec ... 
dev-python/python-exec-0.3.1 (/usr/bin/python-exec)

and this package is :

*  dev-python/python-exec
      Latest version available: 0.3.1
      Latest version installed: 0.3.1
      Size of files: 72 kB
      Homepage:      https://bitbucket.org/mgorny/python-exec/
      Description:   Python script wrapper
      License:       BSD

I don't know what is the function of the /usr/bin/python-exec script?

and why the /usr/bin/pip and /usr/bin.layman will softlink to this script?

now if I want to use pip to install package or layman to manage overlays, I should use /usr/bin/pip-python2.7 and layman-python2.7.

Answer 1

I read the help information of python-exec tool.

I think it is a pygment wapper. There are Formatters, Filters, and so on.

So If I use:

$ python-exec -l python -f html -o /tmp/test.file
#this is the input#
print 'hello world'
....

it will write the input to /tmp/test.file, and use pygments to colorful the code.

But why the pip and layman will softlink to it, I still don't know.

Append:

I have found the reason:

for some reason, some another application overwrite the /usr/bin/python-exec. (I think maybe is pygments.)

The right content is :

#!/usr/bin/python-exec-c                                                                                                                             
# vim:fileencoding=utf-8:ft=python                                               
# (c) 2012 Michał Górny                                                          
# Released under the terms of the 2-clause BSD license.                          
#                                                                                
# This is not the script you are looking for. This is just a wrapper.            
# The actual scripts of this application were installed with -python*,           
# -pypy* or -jython* suffixes. You are most likely looking for one               
# of those.                                                                      

from __future__ import with_statement                                            
import os, os.path, sys                                                          

try:                                                                             
    from epython import EPYTHON                                                  
except ImportError:                                                              
    EPYTHON = os.path.basename(sys.executable)                                   
    if '' and EPYTHON.endswith(''):                                              
        EPYTHON = EPYTHON[:-len('')]                                             

# In the loop:                                                                   
# sys.argv[0] keeps the 'bare' name                                              
# __file__ keeps the 'full' name

while True:                                                                      
    __file__ = sys.argv[0] + '-' + EPYTHON                                       

    try:                                                                         
        kwargs = {}                                                              
        if sys.version_info[0] >= 3:                                             
            import tokenize                                                      

            # need to provide encoding                                           
            with open(__file__, 'rb') as f:                                      
                kwargs['encoding'] = tokenize.detect_encoding(f.readline)[0]     

        with open(__file__, 'r', **kwargs) as f:                                 
            data = f.read()                                                      
    except IOError:                                                              
        # follow symlinks (if supported)                                         
        try:                                                                     
            sys.argv[0] = os.path.join(os.path.dirname(sys.argv[0]),             
                    os.readlink(sys.argv[0]))                                    
        except (OSError, AttributeError):                                        
            # no more symlinks? then it's time to fail.                          
            sys.stderr.write('This Python implementation (%s) is not supported by the script.\n'
                    % EPYTHON)                                                   
            sys.exit(127)
    else:                                                                        
        break                                                                    

sys.argv[0] = __file__                                                           
exec(data)

and many binary files, such as pip, layman will all softlink to it, it is a simple wrapper.

Answer 2

python-exec is a Gentoo-specific wrapper script that invokes an implementation of the requested script appropriate to the currently selected Python runtime. This enables Gentoo to support switching between Python runtimes without breaking scripts, as long as a compatible version of the script exists for the selected runtime.