Read file names from directory in Bash

Question

I need to write a script that reads all the file names from a directory and then depending on the file name, for example if it contains R1 or R2, it will concatenates all th

Answer 1

Simple hack:

ls -al R1 | awk '{print $9}' >outputfilenameR1

ls -al R2 | awk '{print $9}' >outputfilenameR2

Answer 2

To make the smallest change that fixes the problem:

dir="path to the files"
for f in "$dir"/*; do
  cat "$f"
done

To accomplish what you describe as your desired end goal:

shopt -s nullglob
dir="path to the files"
substrings=( R1 R2 )
for substring in "${substrings[@]}"; do
  cat /dev/null "$dir"/*"$substring"* >"${substring}.out"
done

Note that cat can take multiple files in one invocation -- in fact, if you aren't doing that, you usually don't need to use cat at all.