Re: system command takes a different environment variable from current shell?

2015-10-16 19:27 GMT+03:00 Karl (Xiangrong) Cai <xcai@juniper.net>:
> Hi,
> I have a login tcsh which originally has this environment variable c set as
> "/volume/current":
> <<<
> 601% env | grep "SHELL\|current"
> SHELL=tcsh
> c=/volume/current
> XTERM_SHELL=/bin/tcsh
>>>>
>
> And in vim, when I do 1) echo $c, and 2) let x = system("echo $c"); and then
> "echo x", both shows "/volume/current", which is expected;
>
> Then inside this shell I set this variable to another value:
> <<<
> 603% setenv c /volumeNEW/current
> 604% env | grep "SHELL\|current"
> SHELL=tcsh
> c=/volumeNEW/current
> XTERM_SHELL=/bin/tcsh
>>>>
>
> And now in in vim, when I do "echo $c" it shows the new value
> "/volumeNEW/current", but when I use the above mentioned 2nd way, it shows
> the old value "/volume/current". Is it supposed to show the new value?

You need to refer to your shell documentation. The answer to this
question depends on which configuration files shell is sourcing in
different cases. In case of system it is run using something like
`&shell . ' ' .&shellcmdflag . ' ' . shellescape("echo $c")` (use
`strace -e execve -f` to trace what is actually run).

I think that system() is picking up your environment variable, but
shell is overwriting it later with the "default" value sourced from
configuration. To confirm revert to safer options (POSIX shell, which
does not source tcsh configuration, and hopefully no its own: at least
bash aliased to sh does not source any configuration with `sh -c 'echo
true'` as confirmed by strace) and repeat:

set shell=/bin/sh shellcmdflag=-c shellquote= shellxquote=
echo system('echo $c')

.

>
> Am I wrong about how system() is supposed to pick up environment variable?
> Or there is a bug here?
>
> Thanks.
> --Karl
>
>
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