Extracting tag values from XML using perl

Steve_altius · #1 (**permalink**) 08-06-2008

Hi All,

I'm trying to extract the values for the 'src' and 'alt' tags within an xml file. In the files that I'm searching, the tags are always enclosed within an 'img' tag. Typically:

<img src="diwiz01.gif" width="576" height="254" alt="Out-of-process and In-process COM Objects"><bookmark name="f003"/></img>

I grep for 'img' and pipe to the following perl code that successfully extracts the required data:

Code:

#!/usr/bin/perl
while (<>) {
   while (m/img src=\"(.*?)\"/ig) {
      print $1,"|";
      }
   while (m/alt=\"(.*?)\"/ig) {
      print $1,"\n";
      }
      }

However, the xml source occasionally contains the 'src' and 'alt' tags in a different order within the 'img' tag. For example:

<img width="470" height="321" alt="A Remote COM Object" src="dicwiz02.gif"><bookmark name="f004"/></img>

Consequently, the above code doesn't work.

The basis of the code was originally used for a different problem and I didn't write it. I've modified it in an attempt to satisfy this problem. Unfortunately, although I know the basics of sed and awk (but hardly any perl), I'm not a programmer and I'm struggling a bit.

Any help gratefully received.

Thanks.

Yogesh Sawant · #2 (**permalink**) 08-06-2008

replace:

Code:

while (m/img src=\"(.*?)\"/ig) {
    print $1,"|";

with:

Code:

while (m/img(.*?)src=\"(.*?)\"/ig) {
    print $2,"|";

redoubtable · #3 (**permalink**) 08-06-2008

There might be other more clever solutions, but this one works.

[CODE]
Tsunami xml # cat xml
<img width="470" height="321" alt="A Remote COM Object" src="dicwiz02.gif"><bookmark name="f004"/></img>
<img src="diwiz01.gif" width="576" height="254" alt="Out-of-process and In-process COM Objects"><bookmark name="f003"/></img>
Tsunami xml # perl -ne 'print "$1 $2\n" if /<img.*?(?:src|alt)=\"(.*?)\".*?(?:alt|src)=\"(.*?)\".*?<\/img>/;' xml
A Remote COM Object dicwiz02.gif
diwiz01.gif Out-of-process and In-process COM Objects
Tsunami xml #
[CODE]

Steve_altius · #4 (**permalink**) 08-06-2008

Thanks guys. Both solutions work. I appreciate your efforts!

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