Re: Help with String Extraction

[Andreas Kähäri]

On Mon, Sep 16, 2024 at 02:06:22PM -0400, Steve Matzura wrote:
> I'm trying to write a script that does the following:
> 
> 
> In a loop, list certain files in a directory. For each file:
> 
> • Assign a variable to the result of grepping for "<svrinfodesc>" which is
> always present
> 
> • Add 1 to the location of ">" in the string and assign it to a variable
> 
> • Assign the location of "</" in the string to a variable
> 
> • Assign the difference between the above two values to a variable
> 
> • Extract a substring from the original string starting at the first
> positional variable for a length equal to the number of characters in the
> calculated length variable
> 
> • Display the substring
> 
> 
> *** Code ***
> 
> 
> #!/bin/sh
> for f in $(ls *.xml)
> do
>   echo $f # Display the filename
>   stringZ = $(grep -i svrinfodesc $f) # Find the string I want
> 
>   echo $stringZ # Let's see the string
> pos1 = `expr index "$string" \>` + 1 # Position of first character after ">"
>   pos2 = `expr index "$string" \<\/` # Position of first character after the
> string
> len = (pos2 - pos1) # How long will the substring be?
> echo ${stringZ:pos1:len}
> done
> 
> Test Data:
> 
> 
> Create a file (anything.xml will do) with a couple junk lines as long as it
> includes a line containing the grep target, like this one:
> 
> 
> <svrinfodesc>Ham Radio Study Show</svrinfodesc>
> 
> 
> Everything I've read about string extraction says I'm doing it right, but
> nevertheless, the script aborts at that very line. What did I miss?
> 
> 
> Thanks in advance.

Don't do XML parsing in the shell.  Use a tool that does it for you:

        $ xmlstarlet sel -t -v '//svrinfodesc' -nl file
        Ham Radio Study Show

        $ xmllint --xpath '//svrinfodesc/text()' file
        Ham Radio Study Show

For all file with names matching ./*.xml:

        for name in ./*.xml; do
                xmllint --xpath '//svrinfodesc/text()' "$name"
        done >outfile

-- 
Andreas (Kusalananda) Kähäri
Uppsala, Sweden

.