How do you simulate "." or "source" in a perl script ?

[John Strauss]

On 7 Aug 2003 08:21:27 -0700
[email]c_j_marshall@hotmail.com[/email] (Chris Marshall) wrote:

>
> Is there a good way of simulating the bourne shell's "." command - or
> csh's "source" command inside a perl script ?
>
> Specifically I would like to set environment variables inside a perl
> script which are stored inside a separate config file (used by many
> other programs)
>
> At the moment I have a separate ksh script wrapper around my perl
> script which simply does something like
>
> #!/bin/ksh
>
> . /dir/config.sh
>
> /dir/perlscript.pl
>
> but there's got to be a better way than that.
>
> Unfortunately neither "." nor "source" are particularly easy things to
> search for and I've not spotted anything in either perldoc nor
> googling this newsgroup.
>
> I guess I could have the perl script read the config file explicitly
> and act upon what it finds there - but someone must have tackled this
> already.
>
> Thanks
> Chris

Shell::Source
perhaps this CPAN module will do it for you.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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[James Willmore]

> Specifically I would like to set environment variables inside a perl

> script which are stored inside a separate config file (used by many
> other programs)

If you want to set environmental variables from within Perl, %ENV is
the place to set such items. perldoc perlvar for more information.

>
> At the moment I have a separate ksh script wrapper around my perl
> script which simply does something like
>
> #!/bin/ksh
>
> . /dir/config.sh
>
> /dir/perlscript.pl

No offense, but what's the issue with this? It seems like it does
what you wnat it to do. If you want ALL scripts to have the SAME
environmental variables, why not set them from within .profile or
..bashrc or.cshrc or some variation of the three based upon your shell?

>
> but there's got to be a better way than that.
>
> Unfortunately neither "." nor "source" are particularly easy things
> to search for and I've not spotted anything in either perldoc nor
> googling this newsgroup.

Because it's not portable. Perl is designed with portablity in mind.
WIN32 systems don't use '.' or 'source' without some help (ie
Cygwin). Might I suggest you read some more of the Perl
documentation. Perl is not your average scripting language (like
C-Shell, BASH, KSH, etc).

>
> I guess I could have the perl script read the config file explicitly
> and act upon what it finds there - but someone must have tackled
> this already.

This is a workable solution if you can't keep the environmental
variables set in the parent shell. It's also more portable. If you
decide, one day, to run the scripts on a WIN32 machine, then you don't
have to re-invent the wheel to do so. There are several modules to
aid in this task -or- you could roll your own.

HTH

Jim

[Abigail]

Chris Marshall (c_j_marshall@hotmail.com) wrote on MMMDCXXVIII September
MCMXCIII in <URL:news:cb9c7b76.0308070721.2f4cd3f5@posting.goo gle.com>:
&& Is there a good way of simulating the bourne shell's "." command - or
&& csh's "source" command inside a perl script ?
&&
&& Specifically I would like to set environment variables inside a perl
&& script which are stored inside a separate config file (used by many
&& other programs)
&&
&& At the moment I have a separate ksh script wrapper around my perl
&& script which simply does something like
&&
&& #!/bin/ksh
&&
&& . /dir/config.sh
&&
&& /dir/perlscript.pl
&&
&& but there's got to be a better way than that.
&&
&& Unfortunately neither "." nor "source" are particularly easy things to
&& search for and I've not spotted anything in either perldoc nor
&& googling this newsgroup.
&&
&& I guess I could have the perl script read the config file explicitly
&& and act upon what it finds there - but someone must have tackled this
&& already.


An often asked question is 'how to "source" a file', like you do in the
shell, to set one or more environment variables. The easy answer is:
first source the file, then start the program. But what if the file
to source isn't known in advance? Or it's impossible to write a wrapper
script? Put the code below at or near the beginning of your program.

The code below runs in combination with the Korn shell, and probably any
other Bourne shell decendent, including the POSIX shell. I don't know
whether this works in the standard Windows shell - probably not due to
quoting issues, but getting it to run under Cygwin/bash should not be
a problem.

Abigail

my $ENVIRONMENT = "/some/file/with/environment/variables/";

if (@ARGV && $ARGV [0] eq '--sourced_environment') {
shift;
}
else {
if (-f $ENVIRONMENT) {
#
# Now we perform a double exec. The first exec gives us a shell,
# allowing us the source the file with the environment variables.
# Then, from within the shell we re-exec ourself - but with an
# argument that will prevent us from going into infinite recursion.
#
# We cannot do a 'system "source $ENVIRONMENT"', because
# environment variables are not propagated to the parent.
#
# Note the required trickery to do the appropriate shell quoting
# when passing @ARGV back to ourselves.
#
# Also note that the program shouldn't normally be called with
# '--sourced_environment' - if so, pick something else.
#

@ARGV = map {s/'/'"'"'/g; "'$_'"} @ARGV;

exec << " --";
source '$ENVIRONMENT'
exec $0 --sourced_environment @ARGV;
--
die "This should never happen.";
}
}
--
$_ = "\112\165\163\1648\141\156\157\164\150\145\1628\12 0\145"
. "\162\1548\110\141\143\153\145\162\0128\177" and &japh;
sub japh {print "@_" and return if pop; split /\d/ and &japh}

[Chris Marshall]

James Willmore <jwillmore@cyberia.com> wrote in message news:<20030808111536.71614720.jwillmore@cyberia.co m>...

> > Specifically I would like to set environment variables inside a perl
> > script which are stored inside a separate config file (used by many
> > other programs)
> >
> > At the moment I have a separate ksh script wrapper around my perl
> > script which simply does something like
> >
> > #!/bin/ksh
> >
> > . /dir/config.sh
> >
> > /dir/perlscript.pl

>
> No offense, but what's the issue with this? It seems like it does
> what you wnat it to do. If you want ALL scripts to have the SAME
> environmental variables, why not set them from within .profile or
> .bashrc or.cshrc or some variation of the three based upon your shell?
>

Only that it means having two scripts instead of one - and it seems a
shame that the perl script would be reliable on a ksh script to run.

[Chris Marshall]

Abigail <abigail@abigail.nl> wrote in message news:<slrnbj7gfm.39l.abigail@alexandra.abigail.nl> ...

> Chris Marshall (c_j_marshall@hotmail.com) wrote on MMMDCXXVIII September
> MCMXCIII in <URL:news:cb9c7b76.0308070721.2f4cd3f5@posting.goo gle.com>:
> && Is there a good way of simulating the bourne shell's "." command - or
> && csh's "source" command inside a perl script ?
> &&

> The code below runs in combination with the Korn shell, and probably any
> other Bourne shell decendent, including the POSIX shell. I don't know
> whether this works in the standard Windows shell - probably not due to
> quoting issues, but getting it to run under Cygwin/bash should not be
> a problem.
>

<snip most of the code example>

> exec << " --";
> source '$ENVIRONMENT'
> exec $0 --sourced_environment @ARGV;

Brilliant - thank you.
BTW I changed "source" in your script to be "." to get it working with
ksh. Should source have worked ? I thought that source was just for
csh.