On the one occasion I had cause to do this, I exec'd the
perl script from the login script, and exec'd a new shell
from the perl script. Problem was, that launched the shell
twice - easily solved in my case, as I had the luxury of
making the perl script the login shell for the relevant
users. This also solves the problem of needing to stop
the script from executing twice (either by assuming a
login shell the first time around, or setting an environment
variable from within the script)
As someone else pointed out, passing the output from the
script to a cd command works too. But things complicate
if you want to change more of the environment than just
the directory...
That is (shell script):
# ... stuff run every time this script is invoked
if [ "$checkvar" != "foo" ]; then
exec perl /usr/script/myscript.pl
else
# ... stuff to do after the script has run
fi
And in the perl script:
$ENV{checkvar}="foo";
exec "sh", "/usr/script/myshell.sh" # or, if you're logging in
exec "sh", "-l"
There may be a problem if the shell script is not being
executed as part of a login sequence, as you can't assume
the environment is trustworthy. I suspect in most cases
all someone who fakes the variable is going to do is
make the perl script fail to run...
