Error handling in Ruby scripts

[Peter Bailey]

Hi,
Can someone please help me with exception handling? I've written some
classes and scripts that I've used for a year or two. But now, I'm
having to use them with many thousands of files at once, and, even
though they process just one file at a time, there are sometimes errors
in the tools that I use. Specifically, I use an image processing tool
called Image Alchemy. In my Ruby scripts, I have a class written that
has in it various conversion routines where it converts the file pointed
to in Ruby to various formats--TIFF, PNG, etc., etc. My problem is that
when I'm presented with many thousands of files, I'm getting the odd
input file that's just bad. So, my Alchemy Ruby code fails, because
Alchemy itself is failing with that bad file. So, I've read a bit about
"raise," but, I can't seem to get it to work. Can I use "raise" as an
exception handler in my class? Then, in my scripts, could I use
"begin/rescue" with that exception?

Below is a subset of my class

Thanks,
Peter

class Alchemy
def initialize(file)
@file = file
end
def Alchemy.tiff(file)
`alchemy #{file} -t1 -Zc1 -Zm2 -Za4 -Zd 300 300 .300 -o`
end
def Alchemy.tiffbw(file)
`alchemy #{file} -t204 -Zc1 -Zm2 -Za4 -Zd 600 600 .300 -o`
end
def Alchemy.tiffgray(file)
`alchemy #{file} -t1 -Zc1 -Zm2 -b -c256 -8 -Za4 -Zd 300 300 .300 -o`
end
end

 

[snex]

Hi,
Can someone please help me with exception handling? I've written some
classes and scripts that I've used for a year or two. But now, I'm
having to use them with many thousands of files at once, and, even
though they process just one file at a time, there are sometimes errors
in the tools that I use. Specifically, I use an image processing tool
called Image Alchemy. In my Ruby scripts, I have a class written that
has in it various conversion routines where it converts the file pointed
to in Ruby to various formats--TIFF, PNG, etc., etc. My problem is that
when I'm presented with many thousands of files, I'm getting the odd
input file that's just bad. So, my Alchemy Ruby code fails, because
Alchemy itself is failing with that bad file. So, I've read a bit about
"raise," but, I can't seem to get it to work. Can I use "raise" as an
exception handler in my class? Then, in my scripts, could I use
"begin/rescue" with that exception?

Below is a subset of my class

Thanks,
Peter

class Alchemy
  def initialize(file)
   @file = file
  end
  def Alchemy.tiff(file)
   `alchemy #{file} -t1 -Zc1 -Zm2 -Za4 -Zd 300 300 .300 -o`
  end
  def Alchemy.tiffbw(file)
    `alchemy #{file} -t204 -Zc1 -Zm2 -Za4 -Zd 600 600 .300 -o`
  end
  def Alchemy.tiffgray(file)
    `alchemy #{file} -t1 -Zc1 -Zm2 -b -c256 -8 -Za4 -Zd 300 300 .300 -o`
  end
end

its not going to work the way you are doing it. backquotes cant tell
if the command inside them completed "successfully" or not, they just
run it and return STDOUT. you need to analyze the return status of the
command, then raise an error if it failed.

 

[Peter Bailey]

its not going to work the way you are doing it. backquotes cant tell
if the command inside them completed "successfully" or not, they just
run it and return STDOUT. you need to analyze the return status of the
command, then raise an error if it failed.

OK. Thanks. Well, obviously, I've got to use backquotes or "system" in
this case. Being a Windows command shell program, a successful result
would be "0" in Windows, "1" or anything else if unsuccessful. Can I
capture that as part of my "raise?"

 

[Andrew Timberlake]

OK. Thanks. Well, obviously, I've got to use backquotes or "system" in
this case. Being a Windows command shell program, a successful result
would be "0" in Windows, "1" or anything else if unsuccessful. Can I
capture that as part of my "raise?"

You can get the exit status from $?.exitstatus

Andrew Timberlake
http://ramblingsonrails.com
http://www.linkedin.com/in/andrewtimberlake

"I have never let my schooling interfere with my education" - Mark Twain

 

[Peter Bailey]

You can get the exit status from $?.exitstatus

Andrew Timberlake
http://ramblingsonrails.com
http://www.linkedin.com/in/andrewtimberlake

"I have never let my schooling interfere with my education" - Mark Twain

Thank you. I'll try that.