How can I use awk or Perl to increment a number in a large XML file?

Question

I have an XML file with the following line:

            <VALUE DECIMAL_VALUE="0.2725" UNIT_TYPE="percent"/>

I would like to increment this value by .04 and keep the format of the XML in place. I know this is possible with a Perl or awk script, but I am having difficulty with the expressions to isolate the number.

Answer 1

Something akin to the following will work. It may need tweaking if there is extra spacing, but that is left as an exercise for the reader.

function update_after(in_string, locate_string, delta) {
    local_pos = index(in_string,locate_string);
    leadin    = substr(in_string,0,local_pos-1);
    leadout   = substr(in_string,local_pos+length(locate_string));
    new_value = leadout+delta;
    quote_pos = index(leadout,"\"");
    leadout   = substr(leadout, quote_pos + 1);
    return leadin locate_string new_value"\"" leadout;
}

/^ *\<VALUE/{
    print  update_after($0, "DECIMAL_VALUE=\"",0.4);
}

Answer 2

If you're on a box with the xsltproc command in place I would suggest you use XSLT for this.

For a Perl solution I'd go for using the DOM. Check this DOM Processing with Perl article out.

That said. If your XML file is produced in a predictable way something naïve like the following could work:

perl -pe 's#(<VALUE DECIMAL_VALUE=")([0-9.]+)(" UNIT_TYPE="percent"/>)#"$1" . ($2 + 0.4) . "$3"#e;'

Answer 3

This takes input on stdin, outputs to stdout:

while(<>){
 if( $_ =~ /^(.*DECIMAL_VALUE=\")(.*)(\".*)$/ ){
  $newVal = $2 + 0.04;
  print "$1$newVal$3\n";
 }else{
  print $_;
 }
}

Answer 4

here's gawk

awk '/DECIMAL_VALUE/{
 for(i=1;i<=NF;i++){
    if( $i~/DECIMAL_VALUE/){
        gsub(/DECIMAL_VALUE=|\042/,"",$i)
        $i="DECIMAL_VALUE=\042"$i+0.4"\042"
    }
 }
}1' file