Asp Forum - problem with ".scan"

Peter Bailey

9/27/2006 2:52:00 PM

RUBY's complaining about the following 3 lines of code. I've got it in a
new program, but, I copied it directly from an older, working program.
Can someone help me understand what's the problem with the "scan" line,
or, apparently, the "each" line?

Thanks,
Peter

10 Dir.glob("*.ps").each do |psfile|
11 file_contents = File.read(psfile)
12 file_contents.scan(/\%\%Pages: (\d{1,5})[ ]+\n/) do

Error message:

E:/PageCounts/test1.rb:12:in `scan': string modified (RuntimeError)
from E:/PageCounts/test1.rb:12
from E:/PageCounts/test1.rb:10:in `each'
from E:/PageCounts/test1.rb:10

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17 Answers

Ara.T.Howard

9/27/2006 3:00:00 PM

Peter Bailey

9/27/2006 3:21:00 PM

unknown wrote:
> On Wed, 27 Sep 2006, Peter Bailey wrote:
>
>> 11 file_contents = File.read(psfile)
>> 12 file_contents.scan(/\%\%Pages: (\d{1,5})[ ]+\n/) do
>
> the modification is probably here. can't you show us everything up
> through
> the matching end?
>
> -a

Sorry. It's a bit much. That's why I was holding back. Here's the whole
script.

require 'kirbybase'
Dir.chdir("E:/pagecounts")
#First, create the database table.
db = KirbyBase.new
# If table exists, delete it.
db.drop_table(:pageinfo) if db.table_exists?(:pageinfo)
pageinfo_tbl = db.create_table(:pageinfo,
:filename, {:DataType=>:String,
:Index=>1},
:lconstant, :String,
:compcode, :String,
:primecode, :Integer,
:costcenter, :String,
:acctgroup, :Integer,
:blank, :String,
:description, :String,
:pagecount, :Float,
:sjccode, :String,
:fullname, {:DataType=>:String,
:Index=>2}
)
# Import the csv file.
pageinfo_tbl.import_csv('McArdle_indexes.csv')

=begin
Parse each postscript print file in the polled directory. Create
variables for:
the number of pages in each file; the number of blank pages in each
file; and,
what exact pages are blank.
=end
Dir.glob("*.ps").each do |psfile|
file_contents = File.read(psfile)
file_contents.scan(/\%\%Pages: (\d{1,5})[ ]+\n/) do
totalpages = $1
if (totalpages.to_i % 2) !=0 then
newtotalpages = totalpages.to_i + 1
file_contents << "\%\%Blank page for Asura.\n\%\%Page:
#{newtotalpages.to_i}\nshowpage\n"
File.open(psfile, "w") { |f| f.print file_contents }
FileUtils.touch(psfile)
end

=begin
Find blank pages in the postscript file. Look for the regular expression
that
sees a page callout followed by postscript data that does not include
data in parentheses. Any type on a postscript page is enclosed in
parentheses,
so, that's why this is a legitimate search. Blank pages have no
parenthesized
data.
=end
blanks = []
file_contents.scan(/\%\%Page: [()0-9{1,5}]
([0-9]{1,5})\n[^$.*$]\%\%Page/)
do |match|
blanks.push($1)
end
file_contents.scan(/\%\%Blank page for Asura.\n/) do |match|
blanks.push(totalpages.to_i + 1)
end

=begin
Open a "pageinfo" file. Put page information about the file into it.
Notice that the variable for the total number of pages differs depending
on whether a "newtotalpages" variable exists. And, that variable only
exists if the original page count was odd and a blank had to be added.
=end
filename = File.basename("#{psfile}", '.ps')
pageinfofile = File.basename("#{psfile}", '.ps') + ".pageinfo"
File.open("E:/pagecounts/#{pageinfofile}", "a") do |fileinfo|
if newtotalpages then
fileinfo << #{filename}\n << "Total number of pages in this PDF:
#{newtotalpages}\n" <<
"Number of blank pages in this PDF: #{blanks.size}\n" <<
"Specific pages that are blank in this PDF: " <<
"#{blanks.join(', ')}\n"
else
fileinfo << #{filename}\n <<
"Total number of pages in this PDF: #{totalpages}\n" <<
"Number of blank pages in this PDF: #{blanks.size}\n" <<
"Specific pages that are blank in this PDF: " <<
"#{blanks.join(', ')}\n"
end
end
end
end

=begin
Back to the database table. . . .
Query against the table and match the filename in the directory with
whichever entry
in the "filename" column of the table matches. Then, if there's a match,
populate
the "pagecount" field in that row of the table with the variable for the
page count, as
found above. That variable name is "newtotalpages."
=end

Dir.glob("*.ps").each do |dirfile|
result = pageinfo_tbl.select(:filename) { |r| dirfile =~
Regexp.new(r.filename) }
pageinfo_tbl.update { |r| r.name ==
{filename}.set(:pagecount=>#{newtotalpages}) } unless result.nil?
end

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Paul Lutus

9/27/2006 3:24:00 PM

Peter Bailey wrote:

> RUBY's complaining about the following 3 lines of code. I've got it in a
> new program, but, I copied it directly from an older, working program.
> Can someone help me understand what's the problem with the "scan" line,
> or, apparently, the "each" line?
>
> Thanks,
> Peter
>
>
> 10 Dir.glob("*.ps").each do |psfile|
> 11 file_contents = File.read(psfile)
> 12 file_contents.scan(/\%\%Pages: (\d{1,5})[ ]+\n/) do

Whoa. The error message suggests that the source string is being modified
while being read, but your listing stops before the part where that might
happen.

> Error message:
>
> E:/PageCounts/test1.rb:12:in `scan': string modified (RuntimeError)

It's always a good idea to post a short working example in a case like this,
not just the part where you think the problem is. That would have provided
us with the true problem area.

--
Paul Lutus
http://www.ara...

Ara.T.Howard

9/27/2006 3:36:00 PM

Peter Bailey

9/27/2006 5:46:00 PM

unknown wrote:
> On Thu, 28 Sep 2006, Peter Bailey wrote:
>
>>> -a
>>
>> Sorry. It's a bit much. That's why I was holding back. Here's the whole
>> script.
>
> <snip>
>
>> Dir.glob("*.ps").each do |psfile|
>> file_contents = File.read(psfile)
>> file_contents.scan(/\%\%Pages: (\d{1,5})[ ]+\n/) do
>> totalpages = $1
>> if (totalpages.to_i % 2) !=0 then
>> newtotalpages = totalpages.to_i + 1
>> file_contents << "\%\%Blank page for Asura.\n\%\%Page:
> ^^
> ^^
> ^^
> ^^
> the modification is question
>> #{newtotalpages.to_i}\nshowpage\n"
>> File.open(psfile, "w") { |f| f.print file_contents }
>> FileUtils.touch(psfile)
>> end
>
> so, ruby is correct, you are modifying a string while in an in-progress
> scan
> block. easy-cheasy.
>
> kind regards.
>
> -a

Thanks. I ended the scan block before doing any file writing. That
seemed to do the trick. It still confuses me, though, because, this code
was borrowed from an existing script that I've been using for 6 months,
and, that part of it is just as you see it above.

--
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Ara.T.Howard

9/27/2006 6:00:00 PM

Peter Bailey

9/27/2006 6:18:00 PM

unknown wrote:
> On Thu, 28 Sep 2006, Peter Bailey wrote:
>
>>>> Dir.glob("*.ps").each do |psfile|
>>> the modification is question
>>>
>>> -a
>>
>>
>> Thanks. I ended the scan block before doing any file writing. That
>> seemed to do the trick. It still confuses me, though, because, this code
>> was borrowed from an existing script that I've been using for 6 months,
>> and, that part of it is just as you see it above.
>
> probably because totalpages is always 1 - it's never even - in your new
> script
> the number of pages is always 2 (or 0) i'm guessing, and so the bug is
> triggered. if i we're you i'd update the other script - it's a bug in
> waiting.
>
> regards.
>
> -a

Well, I know that they're not always odd or even. They've been a mix of
both. But, I understand what you're saying. I will change my original
script. Basically, and, please tell me if I understand this correctly:
if I'm going to do a scan of a file, open the file, scan it, and then
close it. Right?

--
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Ara.T.Howard

9/27/2006 6:27:00 PM

Peter Bailey

9/27/2006 7:39:00 PM

unknown wrote:
> On Thu, 28 Sep 2006, Peter Bailey wrote:
>
>> Well, I know that they're not always odd or even. They've been a mix of
>> both. But, I understand what you're saying. I will change my original
>> script. Basically, and, please tell me if I understand this correctly:
>> if I'm going to do a scan of a file, open the file, scan it, and then
>> close it. Right?
>
> yup. just remember to avoid this
>
> string = 'foobar'
>
> string.scan(%r/foo/) do |word|
> string << 'foo' # can't modify while scanning
> end
>
> regards.
>
> -a

Thanks a lot, -a! I've cleaned up my code. But, if you notice way above,
I've got a File.read in the line before the file scan. If I do an "end"
for the file scan, my "read" is still open, right? Meaning, I can still
do stuff to the open file.

--
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Robert Klemme

9/27/2006 7:57:00 PM

Peter Bailey <pbailey@bna.com> wrote:
> unknown wrote:
>> On Thu, 28 Sep 2006, Peter Bailey wrote:
>>
>>> Well, I know that they're not always odd or even. They've been a
>>> mix of both. But, I understand what you're saying. I will change my
>>> original script. Basically, and, please tell me if I understand
>>> this correctly: if I'm going to do a scan of a file, open the file,
>>> scan it, and then close it. Right?
>>
>> yup. just remember to avoid this
>>
>> string = 'foobar'
>>
>> string.scan(%r/foo/) do |word|
>> string << 'foo' # can't modify while scanning
>> end
>>
>> regards.
>>
>> -a
>
> Thanks a lot, -a! I've cleaned up my code. But, if you notice way
> above, I've got a File.read in the line before the file scan. If I do
> an "end" for the file scan, my "read" is still open, right? Meaning,
> I can still do stuff to the open file.

If you're referring to your original code, then no. You use File.read(name)
which returns the whole file in a single string. No open connection is
returned.

Btw, for efficiency reasons if your files are large you might consider using

File.foreach(file_name) do |line|
....
end

Or use File.readlines instead of File.read - that way you get an array with
lines and not the whole file in one piece.

Kind regards

robert

comp.lang.ruby

problem with ".scan"

Peter Bailey

Ara.T.Howard

Peter Bailey

Paul Lutus

Ara.T.Howard

Peter Bailey

Ara.T.Howard

Peter Bailey

Ara.T.Howard

Peter Bailey

Robert Klemme

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