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.

grep .txt will likely match more than you wanted; try grep '\.txt$'. Generally, consider using find` for enumerating files in directory subtrees, because it is much more flexible; the equivalent of your command using find is find . -type f -name '*.txt' -exec basename {} + — mklement0
– mklement0, Commented Apr 21, 2014 at 22:21

ooga · Accepted Answer · 2014-04-21 20:09:37Z

3

Put quotes around it:

file="$filename.txt"

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

edited Apr 21, 2014 at 20:09

answered Apr 20, 2014 at 19:36

ooga

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4 Comments

glenn jackman Over a year ago

Strictly speaking, you don't need quotes on variable assignments (reference: "Word splitting is not performed [...]. Filename expansion is not performed.") -- whereever $file is used, that's where the quotes are needed.

glenn jackman Over a year ago

obviously. You're describing gnu.org/software/bash/manual/… not variable assignment.

ooga Over a year ago

Oh, I see what you mean. If it's a variable whose contents contains spaces it'll work without the quotes. Interesting.

glenn jackman Over a year ago

Here's a demo: touch foobar: x=foo*; echo "$x"; echo $x

mklement0 · Accepted Answer · 2014-04-21 22:16:39Z

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.

edited Apr 21, 2014 at 22:16

mklement0

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answered Apr 20, 2014 at 20:03

user3554724

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1 Comment

mklement0 Over a year ago

Note that ls -R | grep .txt returns text files anywhere in the current folder's subtree , whereas your test run with ls -l only happens to work if the specified text file is directly in the current folder.

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