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<TITLE>The Answer Gang 91: Combining multiple PDFs into one</TITLE>
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Combining multiple PDFs into one</H3>
<p><strong>From Faber Fedor
</strong></p>
<p></strong></p>
<p align="right"><strong>Answered By Ben Okopnik, Yann Vernier
</strong></p>
<blockquote><code><font color="#000033"><br>From the chaos of creation
<br>just the final form survives
<br>-- The World Inside The Crystal, Steve Savitsky
</font></code></blockquote>
<blockquote><em><font color="#000066">We could have just posted the finished script in 2c tips. but there's
juicy perl bits to learn from the crafting. Enjoy.
-- Heather</font></em></blockquote>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Hey Gang,
</STRONG></P>
<P><STRONG>
I was playing with my new scanner last night (under a legacy OS
unfortunately) when I realized a shortcoming: I wanted all of the
scanned pages to be in one PDF file, not in separate ones. Well, to that
end, I threw together this quick and dirty Perl script to do just that.
</STRONG></P>
<P><STRONG>
The script assumes you have Ghostscript and pdf2ps installed. It takes
two arguments: the name of the output file and a directory name that
contains all of the PDFs (which have .pdf extensions) to be combined,
e.g.
</STRONG></P>
<pre><strong> ./combine-pdf.pl test.pdf test/
</strong></pre>
<P><STRONG>
I'm sure you can point out many flaws with the script (like how I grab
the command line arguments and clean up after myself), but that's why
it's "quick and dirty". If/when I clean it up, I'll repost it.
</STRONG></P>
<p align="center">See attached <tt><a href="../misc/tag/combine-pdf-faber1,pl.txt">combine-pdf-faber1,pl.txt</a></tt></p>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
If you don't mind, I'll toss in some ideas.
<IMG SRC="../../gx/dennis/smily.gif" ALT=":)"
height="24" width="20" align="middle"> See my version at the end.
</blockQuote>
<blockquote><pre>#!/usr/bin/perl -w
use strict;
</pre></blockquote>
<blockQuote>
Good idea on both.
</blockQuote>
<blockquote><pre># n21pdf.pl: A quick and dirty little program to convert multiple PDFs
# to one PDF requires pdf2ps and Ghostscript
# written by Faber Fedor (faber@linuxnj.com) 2003-05-27
if (scalar(@ARGV) != 2 ) {
</pre></blockquote>
<blockQuote>
You don't need 'scalar'. Scalar behavior (which is defined by the
comparison operator) would cause the list to return the number of its
members, so "if ( @ARGV != 2 )" works fine.
</blockQuote>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Okay. I was trying to get ptkdbi (my fave Perl debugger) to show me the
scalar value of @ARGV and the only way was with <TT> scalar()</TT>. That's also
what I found in the Perl Bookshelf.
</STRONG></P>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
This is the same as "$foo = @foo". $foo is going to contain the number
of elements in @foo.
</blockQuote>
<blockquote><pre>my $PDFFILE = shift ;
my $PDFDIR = shift;
</pre></blockquote>
<blockQuote>
You could also just do
</blockQuote>
<blockQuote>
my ( $PDFFILE, $PDFDIR ) = @ARGV;
</blockQuote>
<blockQuote>
Combining declaration and assignment is perfectly valid.
</blockQuote>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Cute. I'll have to remember that.
</STRONG></P>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
</blockQuote>
<blockquote><pre>chomp($PDFDIR);
</pre></blockquote>
<blockQuote>
No need; the "\n" isn't part of @ARGV.
</blockQuote>
<blockquote><pre>$PDFDIR = $PDFDIR . '/' if substr($PDFDIR, length($PDFDIR)-1) ne '/';
</pre></blockquote>
<blockQuote>
Yikes! You could just say "$PDFDIR .= '<TT>/</TT>'"; an extra slash doesn't hurt
anything (part of the POSIX standard, as it turns out).
</blockQuote>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I know, but I <EM>really</EM> don't like seeing "a_dir//a_file". I always
expect it to fail (although it never does).
<IMG SRC="../../gx/dennis/smily.gif" ALT=":-)"
height="24" width="20" align="middle">
</STRONG></P>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Yonn]
I'm no Perlist myself, but my first choice would be:
$foo =~ s%/*$%/%;
</blockQuote>
<blockQuote>
Which simply ensures that the string ends with exactly one <TT>/.</TT>
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
<IMG SRC="../../gx/dennis/smily.gif" ALT="<grin>"
height="24" width="20" align="middle"> That's one of the ten most common "Perl newbie" mistakes that
CLPM wizards listed: "Using s/// where tr/// is more appropriate." When
you're substituting strings, think "s///"; for characters, go with
"tr///".
</blockQuote>
<blockquote><pre>tr#/##s
</pre></blockquote>
<blockQuote>
Better yet, just ignore it; multiple slashes work just fine.
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Yonn]
I did say I'm no perlist. Tr to me would be the translation tool, for
replacing characters, including deletion.
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Yonn]
Yep; that's exactly what it does. However, even the standard utils "tr"
can <em> _compress</em> strings - which is exactly what was needed here (note the
"s"queeze modifier at the end.)
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Yonn]
Thank you. It's a modifier I had not learned but should have noticed in
your mail. The script would have to tack a <TT>/</TT> onto the end of the string
before doing that tr.
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
You're welcome. Yep, either that or use the globbing mechanism the way I
did; it eliminates all the hassle.
</blockQuote>
<blockquote><pre>for ( <$dir/*pdf> ){
=head
Here's the beef, Granny! :)
All you get here are the specified files as returned by "sh".
You could also use the actual "glob" keyword which is an alias for the
internal function that implements <shell_expansion> mechanism.
=cut
# Mung individual PDF to heart's content
...
}
</pre></blockquote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Yonn]
I don't know how to apply it
to the <EM>end</EM> of the string, which is very easy given a regular
expression as the substitute command uses. I'm more used to dealing with
sed. Remember, the input data may well look like "<TT>/foo/bar/</TT>" and not
just "bar/".
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
You can't apply it to the end of the string, but then I'd imagine Faber
would be just as unhappy with <TT>////foo/////bar////.</TT> "tr", as above, will
regularize all of that.
</blockQuote>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
</blockQuote>
<blockquote><pre>opendir(DIR, $PDFDIR) or die "Can't open directory $PDFDIR: $! \n" ;
</pre></blockquote>
<blockQuote>
Take a look at "perldoc -f glob" or read up on the globbing operator
<*.whatever> in "I/O Operators" in perlop. "opendir" is a little clunky
for things like this.
</blockQuote>
<blockquote><pre> `$PDF2PS $file $outfile` ;
</pre></blockquote>
<blockQuote>
Don't use backticks unless you want the STDOUT output from the command
you invoke. "system" is much better for stuff like this and lets you
check the exit status.
</blockQuote>
<blockQuote>
Note - the following is untested but should work.
</blockQuote>
<p align="center">See attached <tt><a href="../misc/tag/combine-pdf-ben1.pl.txt">combine-pdf-ben1.pl.txt</a></tt></p>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Thanks, I've cleaned it up and attached it. there's one thing that I
couldn't make work, but first...
</STRONG></P>
<P><STRONG>
(now looking inside Ben's version)
</STRONG></P>
<pre><strong>die "Usage: ", $0 =~ /([^\/]+)$/, " <outfile.pdf> <directory_of_pdf_files>\n"
unless @ARGV == 2;
</strong></pre>
<P><STRONG>
Uh, that regex there. Take $_, match one or more characters that aren't
a <TT>/</TT> up to the end of line and remember it and place it in $0? Huh?
</STRONG></P>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
Nope - it's exactly the behavior that Jason was talking about. "print"
takes a list - that's why the members are separated by commas. The
"match" operator, =~, says to look in whatever comes before it; "$_"
doesn't require it.
</blockQuote>
<blockquote><pre>print if /gzotz/; # Print $_ if $_ contains "gzotz"
print if $foo =~ /gzotz/; # Print $_ if $foo contains "gzotz"
print $foo if /gzotz/; # Print $foo if $_ contains "gzotz"
</pre></blockquote>
<blockQuote>
So, what I'm doing is looking at what's in "$0", and capturing/returning
the part in the parens as per standard list behavior. It's a cute little
trick.
</blockQuote>
<blockQuote>
I guess I <EM>will</EM> have to do this one soon in my One-Liner articles; it's
a useful little idiom.
</blockQuote>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I had to move a few things around to get it to work. I did have one
problem though
</STRONG></P>
<pre><strong>#convert ps files to a pdf file
system $GS, $GS_ARGS, $filelist
and die "Problem combining files!\n";
</strong></pre>
<P><STRONG>
This did not work no way, no how. I kept getting "<TT>/undefinedfilename</TT>"
from GS no matter how I quoted it (and I used every method I found in
the Perl Bookshelf).
</STRONG></P>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
Hm. I didn't try it, but -
</blockQuote>
<blockquote><pre>perl -we'$a="ls"; $b="-l"; $c="Docs"; system $a, $b, $c and die "Fooey!\n"'
</pre></blockquote>
<blockQuote>
That works fine. I wonder what "gs"s hangup was. Oh, well - you got it
going, anyway. I guess there's not much of a security issue in handing
it to "sh -c" instead of execvp()ing it in this case: the perms will
take care of all that.
</blockQuote>
<P><STRONG>
<IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
To get it to finally work, I did:
</STRONG></P>
<pre><strong>#convert ps files to a pdf file
my $cmd_string = $GS . $GS_ARGS . $filelist ;
system $cmd_string
and die "Problem combining files!\n";
</strong></pre>
<P><STRONG>
<shrug>
</STRONG></P>
<P><STRONG>
Anywho, here's the final (?) working copy:
</STRONG></P>
<p align="center">See attached <tt><a href="../misc/tag/combine-pdf-faber2.pl.txt">combine-pdf-faber2.pl.txt</a></tt></p>
<blockQuote>
<IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
> [Ben]
Cool! Glad I could help.
</blockQuote>
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