Cat content of files to .txt files with common pattern name in bash - bash

Question

I have a series of .dat files and a series of .txt files that have a common matching pattern. I want to cat the content of the .dat files into each respective .txt file with the matching pattern in the file name, in a loop. Example files are:
xfile_pr_WRF_mergetime_regionA.nc.dat
xfile_pr_GFDL_mergetime_regionA.nc.dat
xfile_pr_RCA_mergetime_regionA.nc.dat
#
yfile_pr_WRF_mergetime_regionA.nc.dat
yfile_pr_GFDL_mergetime_regionA.nc.dat
yfile_pr_RCA_mergetime_regionA.nc.dat
#
pr_WRF_mergetime_regionA_final.txt
pr_GFDL_mergetime_regionA_final.txt
pr_RCA_mergetime_regionA_final.txt
What I have tried so far is the following (I am trying to cat the content of all files starting with "xfile" to the respective model .txt file.
#
find -name 'xfile*' | sed 's/_mergetime_.*//' | sort -u | while read -r pattern
do
echo "${pattern}"*
cat "${pattern}"* >> "${pattern}".txt
done

Answer 1

Let me make some assumptions:
All filenames contain _mergetime_* substring.
The pattern is the portion such as pr_GFDL and is essential to
identify the file.
Then would you try the following:
declare -A map # create an associative array
for f in xfile_*.dat; do # loop over xfile_* files
pattern=${f%_mergetime_*} # remove _mergetime_* substring to extract pattern
pattern=${pattern#xfile_} # remove xfile_ prefix
map[$pattern]=$f # associate the pattern with the filename
done
for f in *.txt; do # loop over *.txt files
pattern=${f%_mergetime_*} # extract the pattern
[[ -f ${map[$pattern]} ]] && cat "${map[$pattern]}" >> "$f"
done

Answer 2

If I understood you correctly, you want the following:
- xfile_pr_WRF_mergetime_regionA.nc.dat
- yfile_pr_WRF_mergetime_regionA.nc.dat
----> pr_WRF_mergetime_regionA_final.txt
- xfile_pr_GFDL_mergetime_regionA.nc.dat
- yfile_pr_GFDL_mergetime_regionA.nc.dat
----> pr_GFDL_mergetime_regionA_final.txt
- xfile_pr_RCA_mergetime_regionA.nc.dat
- yfile_pr_RCA_mergetime_regionA.nc.dat
----> pr_RCA_mergetime_regionA_final.txt
So here's what you want to do in the script:
Get all .nc.dat files in the directory
Extra the pr_TYPE_mergetime_region from the file
Append the _final.txt part to the output file
Then actually pipe the cat output onto that file
So I ended up with the following code:
find *.dat | while read -r pattern
do
output=$(echo $pattern | sed -e 's![^(pr)]*!!' -e 's!.nc.dat!!')
cat $pattern >> "${output}_final.txt"
done
And here are the files I ended up with:
pr_GFDL_mergetime_regionA_final.txt
pr_RCA_mergetime_regionA_final.txt
pr_WRF_mergetime_regionA_final.txt
Kindly let me know in the comments if I misunderstood anything or missed anything.

Answer 3

Seems like what you asks for:
concatxy.sh:
#!/usr/bin/env bash
# do not return the pattern if no file matches
shopt -s nullglob
# Iterate all xfiles
for xfile in "xfile_pr_"*".nc.dat"; do
# Regex to extract the common filename part
[[ "$xfile" =~ ^xfile_(.*)\.nc\.dat$ ]]
# Compose the matching yfile name
yfile="yfile_${BASH_REMATCH[1]}.nc.dat"
# Compose the output text file name
txtfile="${BASH_REMATCH[1]}_final.txt"
# Perform the concatenation of xfile and yfile into the .txt file
cat "$xfile" "$yfile" >"$txtfile"
done
Creating populated test files:
preptest.sh:
#!/usr/bin/env bash
# Populating test files
echo "Content of xfile_pr_WRF_mergetime_regionA.nc.dat" >xfile_pr_WRF_mergetime_regionA.nc.dat
echo "Content of xfile_pr_GFDL_mergetime_regionA.nc.dat" >xfile_pr_GFDL_mergetime_regionA.nc.dat
echo "Content of xfile_pr_RCA_mergetime_regionA.nc.dat" >xfile_pr_RCA_mergetime_regionA.nc.dat
#
echo "Content of yfile_pr_WRF_mergetime_regionA.nc.dat" > yfile_pr_WRF_mergetime_regionA.nc.dat
echo "Content of yfile_pr_GFDL_mergetime_regionA.nc.dat" >yfile_pr_GFDL_mergetime_regionA.nc.dat
echo "Content of yfile_pr_RCA_mergetime_regionA.nc.dat" >yfile_pr_RCA_mergetime_regionA.nc.dat
#
#pr_WRF_mergetime_regionA_final.txt
#pr_GFDL_mergetime_regionA_final.txt
#pr_RCA_mergetime_regionA_final.txt
Running test
$ bash ./preptest.sh
$ bash ./concatxy.sh
$ ls -tr1
concatxy.sh
preptest.sh
yfile_pr_WRF_mergetime_regionA.nc.dat
yfile_pr_RCA_mergetime_regionA.nc.dat
yfile_pr_GFDL_mergetime_regionA.nc.dat
xfile_pr_WRF_mergetime_regionA.nc.dat
xfile_pr_RCA_mergetime_regionA.nc.dat
xfile_pr_GFDL_mergetime_regionA.nc.dat
pr_GFDL_mergetime_regionA_final.txt
pr_WRF_mergetime_regionA_final.txt
pr_RCA_mergetime_regionA_final.txt
$ cat pr_GFDL_mergetime_regionA_final.txt
Content of xfile_pr_GFDL_mergetime_regionA.nc.dat
Content of yfile_pr_GFDL_mergetime_regionA.nc.dat
$ cat pr_WRF_mergetime_regionA_final.txt
Content of xfile_pr_WRF_mergetime_regionA.nc.dat
Content of yfile_pr_WRF_mergetime_regionA.nc.dat
$ cat pr_RCA_mergetime_regionA_final.txt
Content of xfile_pr_RCA_mergetime_regionA.nc.dat
Content of yfile_pr_RCA_mergetime_regionA.nc.dat