csh script as executable does not setenv

问题

I am not able to set env variables through an executable csh/tcsh script

An env variable set inside a csh/tcsh executable script "myscript"

contents of the script ...

setenv MYVAR /abc/xyz

which is not able to set on the shell and reports "Undefined variable"

I have made the csh/tcsh script as executable by the following shell command

chmod +x /home/xx/bin/myscript

also the path is updated to

set path = (/home/xx/bin $path)    
which myscript    
/home/xx/bin/myscript

When I run the script on command line and echo the env variable ..

myscript
echo $MYVAR
MYVAR "Undefined variable"

but if i source on command line

source /home/xx/bin/myscript
echo $MYVAR
/abc/xyz

回答1:

you need to source your code rather than execute it so that it is evaluated by the current shell where you want to modify the environment.

You can of course embed

 source /home/xx/bin/myscript

within your .cshrc

the script does not need to be executable or have any #! shebang (though they don't hurt)

回答2:

This is not how environment variables work.

An environment variable is set for a process (in this case, tcsh) which is passed on to all child processes. So when you do:

$ setenv LS_COLORS=foo
$ ls

You first set LS_COLORS for the tcsh process, tcsh then starts the child process ls which inheres tcsh's environment (including LS_COLORS), which it can then use.

However, what you're doing is setting the environment is a child process, and then want to propagate this back to the parent process (somehow). This is not possible. This has nothing to do with tcsh, it works like this for any process on the system.

It works with source because source reads a file, and executes it line-by-line in the current process. So it doesn't start a new tcsh process.

I will leave it as an exercise to you what the implications would mean if it would be possible :-) Do you really want to deal with unwise shell scripts that set some random environment variables? And what about environment variables set by a php process, do we want those to go back in the parent httpd process? :-)

---

You didn't really describe what goal you're trying to achieve, but in general, you want to do something like:

#!/bin/csh -f                                                               

# ... Do stuff ...                                                          

echo "Please copy this line to your environment:"
echo "setenv MYVAR $myvar"

来源：https://stackoverflow.com/questions/28738107/csh-script-as-executable-does-not-setenv