Executing generated commands in bash

Question

I want to run a series of bash commands generated by a Python script. The commands are of the form export foo="bar" and alias foo=bar. They must modify the environment of the current process.

This works great:

$(./generate_commands.py)

until an export command contains a space e.g. export x="a b". This generates an error, and only "a is exported (quotes included).

Currently I'm working around this by outputting generate_commands to a temporary file and sourcing that, but is there a more elegant solution?

"They must modify the environment of the current process." That's not going to work. If you're currently running in python, then, regardless of the exact syntax or method of doing so, running bash in order to evaluate the commands you generated will start a separate process, which by definition cannot influence the environment variables of its parent process. — twalberg
– twalberg, Commented May 2, 2013 at 17:18
@twalberg no, it already does work, the question is whether it can work more elegantly. — Michael Platings
– Michael Platings, Commented May 2, 2013 at 17:25

Alex · Accepted Answer · 2013-05-02 17:09:07Z

5

./generate_commands | bash

This will pipe the output of the script as input to bash

Edit:

To allow for variables to be visible in the current shell, you need to source the output:

source <(./generate_commands)

or

. <(./generate_commands)

edited May 2, 2013 at 17:09

answered May 2, 2013 at 15:56

Alex

11.2k9 gold badges42 silver badges64 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Michael Platings Over a year ago

Apologies for not making it clearer the first time around: the commands are mostly of the form export x=y and must modify the environment of the current process.

Alex Over a year ago

@MichaelPlatings then sourcing is your only way to go, everything else will only modify the subshell environment, answer edited

Michael Platings Over a year ago

I guess that's the answer, thanks. Next problem: print 'export ' + key + '="' + value + '"' IOError: [Errno 32] Broken pipe

Alex Over a year ago

That looks like a python error. Have you executed this manually in a shell, outside of the script? Also try adding set -x or #!/bin/bash -x to view the debug statements made by bash script so that you can see what the lines being executed are, and which, if any, are failing.

Michael Platings Over a year ago

Yes it's a python error. Executing it outside the script gives the same error. I guess python just doesn't play nicely with this method. In case it gives any insight, with bash -x I get the following output: ++ ./generate_commands.py + . /dev/fd/63 ++ echo -ne '\033]0;michael@comp: /my/working/dir\007'

gongzhitaao · Accepted Answer · 2013-05-02 16:23:30Z

0

I think the OP's problem is

cmd="export x=\"a b\""
${cmd}

does not work, but

export x="a b"

works. My way around this is

export x="a"
echo $x
x+=" b"
echo $x

edited May 2, 2013 at 16:23

answered May 2, 2013 at 15:47

gongzhitaao

6,7223 gold badges41 silver badges45 bronze badges

3 Comments

Michael Platings Over a year ago

Interesting idea, but cmd2="x+=\" b\"" ${cmd2} generates an error bash: x+=": command not found

gongzhitaao Over a year ago

@MichaelPlatings Did you put them in a script? it worked on my machine though :)

Michael Platings Over a year ago

Yes. It works when typing the commands directly, but the error occurs running the commands from a script.

Collectives™ on Stack Overflow

Executing generated commands in bash

2 Answers 2

5 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related