On Linux (Ubuntu 11.04 (Natty Narwhal)) in Bash, is it possible to temporarily set an environment variable that will only be different from the normal variable for the duration of the script?
For example, in a shell script, making an application that saves to HOME portable by temporarily setting HOME to a folder in the present working directory, and then launching the application.
VAR1=value1 VAR2=value2 myScript args ...
vblank_mode=0 glxgears. It works, but it also says vblank_mode=0: command not found after running, whereas prepending env doesn't cause this. [testing...] Apparently zsh doesn't like it (yet still uses it correctly), but bash is fine with it. I guess I'll go with the env method from now on.
VAR1="hello" echo $VAR1 does not return anything?
VAR1="hello" bash -c 'echo $VAR1'
export so the variable remains with subprocesses too?env VAR=value myScript args ...
VAR=value myScript args ...
PATH=$PATH:XYZ echo $PATH | grep XYZ doesn't have any output though? 2. What is the difference between using and not using env?
PATH=$PATH:XYZ sh -c 'echo $PATH' | grep XYZ -- the single quotes are the key here
env and not using it?
env gives an error and other shells don't give an error, so I guess it's mostly safer to always use with env.WARNING --- READ THE COMMENTS.
Just put
export HOME=/blah/whatever
at the point in the script where you want the change to happen. Since each process has its own set of environment variables, this definition will automatically cease to have any significance when the script terminates (and with it the instance of bash that has a changed environment).
export will pass the variable to subshells, but it doesn't control the parent shell. If you're writing a script that begins with "#!/bin/sh" or the like, ANY variable you set will disappear when the script exits.
source the script that it will be executed by the same shell that you type the command into.
$HOME to be inherited by any commands executed from the script. And if he doesn't, and the setting of $HOME is only for the benefit of the script itself, then he'd probably be better off modifying the script so it refers to something other than $HOME.
We can use command env to alter environments or just use a simple augment method as bash mannual recording
The environment for any simple command or function may be augmented temporarily by prefixing it with parameter assignments, as described in Shell Parameters. These assignment statements affect only the environment seen by that command.
