sed regex to match ['', 'WR' or 'RN'] + 2-4 digits - regex

Question

I'm trying to do some conditional text processing on Unix and struggling with the syntax. I want to acheive
Find the first 2, 3 or 4 digits in the string
if 2 characters before the found digits are 'WR' (could also be lower case)
Variable = the string we've found (e.g. WR1234)
Type = "work request"
else
if 2 characters before the found digits are 'RN' (could also be lower case)
Variable = the string we've found (e.g. RN1234)
Type = "release note"
else
Variable = "WR" + the string we've found (Prepend 'WR' to the digits)
Type = "Work request"
fi
fi
I'm doing this in a Bash shell on Red Hat Enterprise Linux Server release 5.5 (Tikanga)
Thanks in advance,
Karl

Answer 1

I'm not sure how you read in your strings but this example should help you get there. I loop over 4 example strings, WR1234 RN456 7890 PQ2342. You didn't say what to do if the string doesn't match your expected format (PQ2342 in my example), so my code just ignores it.
#!/bin/bash
for string in "WR1234 - Work Request Name.doc" "RN5678 - Release Note.doc"; do
[[ $string =~ ^([^0-9]*)([0-9]*).*$ ]]
case ${BASH_REMATCH[1]} in
"WR")
var="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"
type="work request"
echo -e "$var\t-- $type"
;;
"RN")
var="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"
type="release note"
echo -e "$var\t-- $type"
;;
"")
var="WR${BASH_REMATCH[2]}"
type="work request"
echo -e "$var\t-- $type"
;;
esac
done
Output
$ ./rematch.sh
WR1234 -- work request
RN5678 -- release note

Answer 2

I like to use perl -pe instead of sed because PERL has such expressive regular expressions. The following is a bit verbose for the sake of instruction.
example.txt:
WR1234 - Work Request name.doc
RN456
rn456
WR7890 - Something else.doc
wr789
2456
script.sh:
#! /bin/bash
# search for 'WR' or 'RN' followed by 2-4 digits and anything else, but capture
# just the part we care about
records="`perl -pe 's/^((WR|RN)([\d]{2,4})).*/\1/i' example.txt`"
# now that you've filtered out the records, you can do something like replace
# WR's with 'work request'
work_requests="`echo \"$records\" | perl -pe 's/wr/work request /ig' | perl -pe 's/rn/release note /ig'`"
# or add 'WR' to lines w/o a listing
work_requests="`echo \"$work_requests\" | perl -pe 's/^(\d)/work request \1/'`"
# or make all of them uppercase
records_upper=`echo $records | tr '[:lower:]' '[:upper:]'`
# or count WR's
wr_count=`echo "$records" | grep -i wr | wc -l`
echo count $wr_count
echo "$work_requests"

Answer 3

#!/bin/bash
string="RN12344 - Work Request Name.doc"
echo "$string" | gawk --re-interval '
{
if(match ($0,/(..)[0-9]{4}\>/,a ) ){
if (a[1]=="WR"){
type="Work release"
}else if ( a[1] == "RN" ){
type = "Release Notes"
}
print type
}
}'