Extract filename and extension in Bash

Question

I want to get the filename (without extension) and the extension separately.

The best solution I found so far is:

NAME=`echo \"$FILE\" | cut -d\'.\'          


        

Answer 1

Here is code with AWK. It can be done more simply. But I am not good in AWK.

filename$ ls
abc.a.txt  a.b.c.txt  pp-kk.txt
filename$ find . -type f | awk -F/ '{print $2}' | rev | awk -F"." '{$1="";print}' | rev | awk 'gsub(" ",".") ,sub(".$", "")'
abc.a
a.b.c
pp-kk
filename$ find . -type f | awk -F/ '{print $2}' | awk -F"." '{print $NF}'
txt
txt
txt

Answer 2

No need to bother with awk or sed or even perl for this simple task. There is a pure-Bash, os.path.splitext()-compatible solution which only uses parameter expansions.

Reference Implementation

Documentation of os.path.splitext(path):

Split the pathname path into a pair (root, ext) such that root + ext == path, and ext is empty or begins with a period and contains at most one period. Leading periods on the basename are ignored; splitext('.cshrc') returns ('.cshrc', '').

Python code:

root, ext = os.path.splitext(path)

Bash Implementation

Honoring leading periods

root="${path%.*}"
ext="${path#"$root"}"

Ignoring leading periods

root="${path#.}";root="${path%"$root"}${root%.*}"
ext="${path#"$root"}"

Tests

Here are test cases for the Ignoring leading periods implementation, which should match the Python reference implementation on every input.

|---------------|-----------|-------|
|path           |root       |ext    |
|---------------|-----------|-------|
|' .txt'        |' '        |'.txt' |
|' .txt.txt'    |' .txt'    |'.txt' |
|' txt'         |' txt'     |''     |
|'*.txt.txt'    |'*.txt'    |'.txt' |
|'.cshrc'       |'.cshrc'   |''     |
|'.txt'         |'.txt'     |''     |
|'?.txt.txt'    |'?.txt'    |'.txt' |
|'\n.txt.txt'   |'\n.txt'   |'.txt' |
|'\t.txt.txt'   |'\t.txt'   |'.txt' |
|'a b.txt.txt'  |'a b.txt'  |'.txt' |
|'a*b.txt.txt'  |'a*b.txt'  |'.txt' |
|'a?b.txt.txt'  |'a?b.txt'  |'.txt' |
|'a\nb.txt.txt' |'a\nb.txt' |'.txt' |
|'a\tb.txt.txt' |'a\tb.txt' |'.txt' |
|'txt'          |'txt'      |''     |
|'txt.pdf'      |'txt'      |'.pdf' |
|'txt.tar.gz'   |'txt.tar'  |'.gz'  |
|'txt.txt'      |'txt'      |'.txt' |
|---------------|-----------|-------|

Test Results

All tests passed.

Answer 3

I use the following script

$ echo "foo.tar.gz"|rev|cut -d"." -f3-|rev
foo

Answer 4

Building from Petesh answer, if only the filename is needed, both path and extension can be stripped in a single line,

filename=$(basename ${fullname%.*})

Answer 5

If you also want to allow empty extensions, this is the shortest I could come up with:

echo 'hello.txt' | sed -r 's/.+\.(.+)|.*/\1/' # EXTENSION
echo 'hello.txt' | sed -r 's/(.+)\..+|(.*)/\1\2/' # FILENAME

1st line explained: It matches PATH.EXT or ANYTHING and replaces it with EXT. If ANYTHING was matched, the ext group is not captured.

Answer 6

~% FILE="example.tar.gz"

~% echo "${FILE%%.*}"
example

~% echo "${FILE%.*}"
example.tar

~% echo "${FILE#*.}"
tar.gz

~% echo "${FILE##*.}"
gz

For more details, see shell parameter expansion in the Bash manual.