bash shell script automaticall add on file extension

Question

Hello so today i was playing around with my shell script and figured to make it more user friendly i would make it so the file extension of file was automatically added.

for example say the user wants to search a file using grep but first they must type in thhe name of the file in this case lets say file.txt what i want to do is automatically add on the .txt so the user only needs to type in "file"

here is what i have so far but this does not work:

echo "Current .txt files "
        ls -R |grep .txt
        echo "--------------------------------------------------------------------------------"
                echo -n "Please select a file to search in: "
                read fileName
                file=$fileName.txt

i thought in this case since i am appending an extension on to the end of the variable name but this has not worked.

Answer 1

Put quotes around it:

file="$filename.txt"

EDIT: As it happens, this answer is incorrect. See the comments below and the other answer.

Answer 2

Your code should work. See below-

Contents of test.sh :

#!/bin/bash

echo "Current .txt files "
        ls -R |grep .txt
        echo "--------------------------------------------------------------------------------"
                echo -n "Please select a file to search in: "
                read fileName
                file=$fileName.txt

echo "You are searching for $file"
ls -l "$file"

Test run:

$ ./test.sh
Current .txt files
p1.txt
t1.txt
t2.txt
--------------------------------------------------------------------------------
Please select a file to search in: t2
You are searching for t2.txt
-rw-r----- 1 d1rld1f1 d1rld1f1 4 Apr 20 12:41 t2.txt
$

BTW, it is generally advisable to enclose variable names in double quotes. This prevents reinterpretation of all special characters within the quoted string.