Dan Huston am Dienstag, 10. Januar 2006 21.40:
> Greetings --
>
> I am reading text sql commands) from a file, chopping it into sections
> and then writing each section out to a different file. Within the text
> are perl variables that I had expected to be interpolated as they were
> written out to the new file but they are not.
>
> Here is a sample line:
>
> REVOKE SELECT ON $TABLE_NAME FROM PUBLIC;
>
> $TABLE_NAME for example might be 'STUDENTS'.
>
> Is there a reason that the text is not being interpolated when before it
> is written out to the new file (either when it is read in or when it is
> printed out)?
>
> Here is a piece of my code:
>
>
> ########## CODE SNIPPET #####################
>
> for $k ( @these_lines ) {
>
> # for debugging
> print "$TABLE_NAME\n";
> print "K\t=>\t$k\n";
>
> ### SQL_OUT is the filehandle that I am writing to
> print SQL_OUT "$k\n";
$k _itself_ is interpolated into the double quoted string: $k contains a
string with content looking like perl vars, $k is replaced by this string.
But there is - luckily! - no second level interpolation included (the
variable names _in_ the string _in_ variable $k).
You would have to make the second level interpolation explicit
my $var='hi!';
print eval "q(He said $var and disappeared)";
=>He said hi! and disappeared
but this is DANGEROUS since the text could contain code instead of simple
variable names.
There may be a useful templating module on search.cpan.org.
Or you could reinvent the wheel and parse for the variable names and replace
them with values. Something along the lines
use strict;
use warnings;
my %vars=(TABLE_NAME=>'STUDENTS');
my @these_lines=('REVOKE SELECT ON $TABLE_NAME FROM PUBLIC $UNKNOWN;');
for (@these_lines) {
s/\$([_a-zA-Z]\w*)/$vars{$1} || '$'.$1/eg;
}
print @these_lines;
>
> } ### CLOSE-FOR-K
>
>
> produces this output in STDOUT:
>
> TABLE_NAME => STUDENTS
> K => REVOKE SELECT ON $TABLE_NAME FROM PUBLIC;
>
> where I want to have :
>
> K => REVOKE SELECT ON STUDENTS FROM PUBLIC;
>
>
> ########## CODE SNIPPET #####################
>
>
> Thanks
> Dan
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