Running multiple command line after each other linux python

Question

I want to run multiple commands in the same line after the previous is done.

I do the following bellow in a python script:

os.system("start_view myView && perl /home/user/Development/count_test.pl -rev 001 -project myproject && /usr/bin/python /home/user/Development/setDoneFlag_Count_Lines.py")

First I set a view in clearcase start_view myview, then I want to execute a perl program. Problem is it doesn't, it just sets the view (which I need in order for me to execute the perl program) but it never actually starts the perl program, so the question is am I doing anything wrong? It seems like start_view myView starts a new shell, so how do I execute a perl script in the newly created shell that the view starts?

Thanks in advance.

Have you tried ; instead of && ? Perhaps the first command returns unsuccessfully. — RobEarl
– RobEarl, Commented May 22, 2015 at 13:45
If start_view is starting a new shell, it may simply not be returning. Perhaps start_view takes an option to allow it to start a process in the shell that it creates. — William Pursell
– William Pursell, Commented May 22, 2015 at 13:49
If this is like ClearCase, start_view will have an option (e.g. -c) where you can give it a command to run in the shell that has been launched in the view's context; if it exists, move the rest of your command into there. Additionally, && short-circuits upon failure (i.e. non-zero status), but ; does not (i.e. each command runs in succession). You can also do || for reverse short-circuit (i.e. execute only if there's a failure). For example try: /bin/true && echo TRUE || echo FALSE and /bin/false && echo TRUE || echo FALSE — kjpires
– kjpires, Commented May 22, 2015 at 14:12
Are you using Rational ClearCase's startview? Maybe you want setview -c your_commands_here? setview doc — rickhg12hs
– rickhg12hs, Commented May 22, 2015 at 14:13

mhawke · Accepted Answer · 2015-05-22 13:50:12Z

1

In general multiple dependent commands should work when invoked from os.system():

>>> rv = os.system("ls /dev/null && grep mhawke /etc/passwd")
/dev/null
mhawke:x:1000:1000:mhawke:/home/mhawke:/bin/bash
>>> rv
0

But if one command fails (as determined by a non-zero exit status) the following commands are not executed:

>>> rv = os.system("ls /phantom && grep mhawke /etc/passwd")
ls: cannot access /phantom: No such file or directory
>>> rv
512

So, are you sure that start_view returns exit code 0? Are you sure that start_view returns at all? - could it be blocked waiting for input. Are you sure that the command isn't actually startview myView?

You could find out by executing this on the command line:

$ start_view myView
$ echo $?

If it displays 0, then try the next command in the chain until you find the culprit.

answered May 22, 2015 at 13:50

mhawke

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