pushd through os.system

Asked 2011-05-31T22:57:14.010

I'm using a crontab to run a maintenance script for my minecraft server. Most of the time it works fine, unless the crontab tries to use the restart script. If I run the restart script manually, there aren't any issues. Because I believe it's got to do with path names, I'm trying to make sure it's always doing any minecraft command FROM the minecraft directory. So I'm encasing the command in pushd/popd:

os.system("pushd /directory/path/here")
os.system("command to sent to minecraft")
os.system("popd")

Below is an interactive session taking minecraft out of the equation. A simple "ls" test. As you can see, it does not at all run the os.system command from the pushd directory, but instead from /etc/ which is the directory in which I was running python to illustrate my point.Clearly pushd isn't working via python, so I'm wondering how else I can achieve this. Thanks!

>>> def test():
...     import os
...     os.system("pushd /home/[path_goes_here]/minecraft")
...     os.system("ls")
...     os.system("popd")
... 
>>> test()
~/minecraft /etc
DIR_COLORS    cron.weekly  gcrypt         inputrc    localtime   mime.types         ntp       ppp         rc3.d       sasldb2         smrsh      vsftpd.ftpusers
DIR_COLORS.xterm  crontab      gpm-root.conf      iproute2   login.defs  mke2fs.conf            ntp.conf      printcap        rc4.d       screenrc        snmp       vsftpd.tpsave
X11       csh.cshrc    group          issue      logrotate.conf  modprobe.d         odbc.ini      profile         rc5.d       scsi_id.config  squirrelmail   vz
adjtime       csh.login    group-         issue.net  logrotate.d     motd               odbcinst.ini  profile.d       rc6.d       securetty       ssh        warnquota.conf
aliases       cyrus.conf   host.conf      java       lvm         mtab               openldap      protocols       redhat-release  security        stunnel        webalizer.conf
alsa          dbus-1



        
            2 Answers
            
            
                
                    
                        
                            
                            
                        
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                        I don't think you can call pushd from within an os.system() call:

>>> import os
>>> ret = os.system("pushd /tmp")
sh: pushd: not found


Maybe just maybe your system actually provides a pushd binary that triggers a shell internal function (I think I've seen this on FreeBSD beforeFreeBSD has some tricks like this, but not for pushd), but the current working directory of a process cannot be influenced by other processes -- so your first system() starts a shell, runs a hypothetical pushd, starts a shell, runs ls, starts a shell, runs a hypothetical popd... none of which influence each other.

You can use os.chdir("/home/path/") to change path: http://docs.python.org/library/os.html#os-file-dir

                        
                        
                            answered 2011-05-31T23:02:11.917
                            
                        
                        
                            
                                
                                
                            
                        
                        
                            
                            
                            
                                
                                
                            
                            
                        
                    
                
            
            
            
                
                    
                        
                            
                            
                        
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                        No need to use pushd -- just use os.chdir:

>>> import os
>>> os.getcwd()
'/Users/me'
>>> os.chdir('..')
>>> os.getcwd()
'/Users'
>>> os.chdir('me')
>>> os.getcwd()
'/Users/me'


                        
                        
                            answered 2011-05-31T23:03:16.567
                            
                        
                        
                            
                                
                                
                            
                        
                        
                            
                            
                            
                                
                                
                            
                            
                        
                    
                
            
            
        

        
        
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