create and rename multiple copies of files - bash

Question

I have a file input.txt that looks as follows.
abas_1.txt
abas_2.txt
abas_3.txt
1fgh.txt
3ghl_1.txt
3ghl_2.txt
I have a folder ff. The filenames of this folder are abas.txt, 1fgh.txt, 3ghl.txt. Based on the input file, I would like to create and rename the multiple copies in ff folder.
For example in the input file, abas has three copies. In the ff folder, I need to create the three copies of abas.txt and rename it as abas_1.txt, abas_2.txt, abas_3.txt. No need to copy and rename 1fgh.txt in ff folder.
Your valuable suggestions would be appreciated.

Answer 1

You can try something like this (to be run from within your folder ff):
#!/bin/bash
while IFS= read -r fn; do
[[ $fn =~ ^(.+)_[[:digit:]]+\.([^\.]+)$ ]] || continue
fn_orig=${BASH_REMATCH[1]}.${BASH_REMATCH[2]}
echo cp -nv -- "$fn_orig" "$fn"
done < input.txt
Remove the echo if you're happy with it.
If you don't want to run from within the folder ff, just replace the line
echo cp -nv -- "$fn_orig" "$fn"
with
echo cp -nv -- "ff/$fn_orig" "ff/$fn"
The -n option to cp so as to not overwrite existing files, and the -v option to be verbose. The -- tells cp that there are no more options beyond this point, so that it will not be confused if one of the files starts with a hyphen.

Answer 2

using for and grep :
#!/bin/bash
for i in $(ls)
do
x=$(echo $i | sed 's/^\(.*\)\..*/\1/')"_"
for j in $(grep $x in)
do
cp -n $i $j
done
done

Answer 3

Try this one
#!/bin/bash
while read newFileName;do
#split the string by _ delimiter
arr=(${newFileName//_/ })
extension="${newFileName##*.}"
fileToCopy="${arr[0]}.$extension"
#check for empty : '1fgh.txt' case
if [ -n "${arr[1]}" ]; then
#check if file exists
if [ -f $fileToCopy ];then
echo "copying $fileToCopy -> $newFileName"
cp "$fileToCopy" "$newFileName"
#else
# echo "File $fileToCopy does not exist, so it can't be copied"
fi
fi
done
You can call your script like this:
cat input.txt | ./script.sh

Answer 4

If you could change the format of input.txt, I suggest you adjust it in order to make your task easier. If not, here is my solution:
#!/bin/bash
SRC_DIR=/path/to/ff
INPUT=/path/to/input.txt
BACKUP_DIR=/path/to/backup
for cand in `ls $SRC_DIR`; do
grep "^${cand%.*}_" $INPUT | while read new
do
cp -fv $SRC_DIR/$cand $BACKUP_DIR/$new
done
done