Change directory not successfully done

[Mike Meyer]

Samuel Yin <samuel.yin at 163.com> writes:
> Hi, guys,
>
> This should be a simple problem, but I just can not resolve it. I just
> want to use a python script to change my working directory. see my
> following code:
>
> # mycd.py
> 1) destdir = "xxxxxxxx"
> 2) command = "cd "+ destdir
> 3) os.system(command)
> 4) os.chdir(destdir)
>
> But neither 3) nor 4) is used, I just can not change the directory after
> execute mycd.py. This remind me of bash script. If you change directory
> in your bash script file, it will only impact the sub process of that
> script, except that you invoke that bash script by ./script_file_name.
> But what should I do in the case of python script?

Actually, one solution is a level of indirection worse than the bash
script. Doing a cd changes the current directory of the process that
executes the cd system call. In a bash script, it's the shell
executing the script. In your python script, os.system launches
another process to run the command, and it's *that* process that has
it's directory changed. The os.chdir changes the shell of the python
interpreter, which still doesn't do you any good.

One solution is to switch to a shell that understands Python, and have
that execfile your script. There is a Python environment that can be
configured to be used as a shell, but I can't remeber it's name.

If you want to stay with bash, your solutions are the same as they are
for setting an environment variable in the parent shell.  You can
google for that for a long discussion of the issues.

The solution I liked from that thread was an alias:

In your bash do: alias mycd="eval $(python mycd.py)"

mycd.py looks like:
destdir = 'xxxxxx'
command = 'os ' + destdir
print command

At the bash prompt you enter the command "mycd", your python script
builds a command for the shell to execute and prints it, the eval
reads that output and executes it in your shell.

If you want to pass arguments to the python script, you'll need to use
a shell function instead of an alias.

     <mike
-- 
Mike Meyer <mwm at mired.org>			http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.