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From: Andrew.Vignaux@comp.vuw.ac.nz (Andrew Vignaux)
Newsgroups: comp.lang.perl
Subject: Re: Question on variable substitution in strings
Message-ID: <1991Jun18.073349.6447@comp.vuw.ac.nz>
Date: 18 Jun 91 07:33:49 GMT
References: <1991Jun18.051149.25411@ccu1.aukuni.ac.nz>
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In article <1991Jun18.051149.25411@ccu1.aukuni.ac.nz>, russell@ccu1.aukuni.ac.nz (Russell J Fulton;ccc032u) writes:
|>   $ddev='ccvcom::sys\$sysdevice:[decnet.uspool]';
|>   system("/usr/bin/dn/dncp $file $ddev$$__$printer"."__$USER"."__$vmsfn"); 
|> 
|> There are two things that puzzle me. One is why do I need to escape the
|> $ in the first statement.

$sysdevice is being interpreted by /bin/sh.

|> The other thing is: why do I need to break the string with a "." after
|> $printer? I could have understood it if I had to break up "$$__" because
|> perl got confused between $$ and $_.

Because '_' is a valid character in an identifier.  An easier
workaround is to use {}s:

    "...__${printer}__..."

To avoid /bin/sh getting its grubbly little hands on your '$'s (or
even worse someone invoking your utility with "USER='; echo gotcha'")
you could invoke:

    system('/usr/bin/dn/dncp', $file, "$ddev$$__${printer}__${USER}__$vmsfn");

i.e. pass the arguments to dncp directly.

Andrew
-- 
Domain address: Andrew.Vignaux@comp.vuw.ac.nz