How can I remove the extension of a filename in a shell script?

Question

What's wrong with the following code?

name='$filename | cut -f1 -d'.''

As is, I get the literal string $filename | cut -f1 -d'.', but if I remove the quotes I don't get anything. Meanwhile, typing

"test.exe" | cut -f1 -d'.'

in a shell gives me the output I want, test. I already know $filename has been assigned the right value. What I want to do is assign to a variable the filename without the extension.

Solution 1

You should be using the command substitution syntax $(command) when you want to execute a command in script/command.

So your line would be

name=$(echo "$filename" | cut -f 1 -d '.')

Code explanation:

1. echo get the value of the variable $filename and send it to standard output
2. We then grab the output and pipe it to the cut command
3. The cut will use the . as delimiter (also known as separator) for cutting the string into segments and by -f we select which segment we want to have in output
4. Then the $() command substitution will get the output and return its value
5. The returned value will be assigned to the variable named name

Note that this gives the portion of the variable up to the first period .:

$ filename=hello.world
$ echo "$filename" | cut -f 1 -d '.'
hello
$ filename=hello.hello.hello
$ echo "$filename" | cut -f 1 -d '.'
hello
$ filename=hello
$ echo "$filename" | cut -f 1 -d '.'
hello

Solution 2

You can also use parameter expansion:

$ filename=foo.txt
$ echo "${filename%.*}"
foo

Just be aware that if there is no file extension, it will look further back for dots, e.g.

• If the filename only starts with a dot (e.g. .bashrc) it will remove the whole filename.
• If there's a dot only in the path (e.g. path.to/myfile or ./myfile), then it will trim inside the path.

Solution 3

If you know the extension, you can use basename

$ basename /home/jsmith/base.wiki .wiki
base

Solution 4

If your filename contains a dot (other than the one of the extension) then use this:

echo $filename | rev | cut -f 2- -d '.' | rev

Solution 5

file1=/tmp/main.one.two.sh
t=$(basename "$file1")                        # output is main.one.two.sh
name=$(echo "$file1" | sed -e 's/\.[^.]*$//') # output is /tmp/main.one.two
name=$(echo "$t" | sed -e 's/\.[^.]*$//')     # output is main.one.two

use whichever you want. Here I assume that last . (dot) followed by text is extension.

View more solutions

Comments

[mpe]

basename $filename .exe would do the same thing. That's assuming you always know what extension you want to remove.

[Charles Duffy]

@mpe, you mean basename "$filename" .exe. Otherwise filenames with spaces would be bad news.

[mimicocotopus]

Thanks. I also noticed that I need to use the echo command. name=echo $filename | cut -f1 -d'.'

[jordanm]

Backticks are deprecated by POSIX, $() is preferred.

[Jens]

Forking and piping to get at a few characters is about the worst solution imaginable.

[Scott Stensland]

The problem with this answer is it assumes input string has ONLY one dot ... @chepner below has a much better solution ... name=${filename%.*}

[Carlos Robles]

here the explanation of the command: gnu.org/software/bash/manual/html_node/…

[user208145]

And here I was about to use echo -n "This.File.Has.Periods.In.It.txt" | awk -F. '{$NF=""; print $0}' | tr ' ' '.' | rev | cut -c 2- | rev. Thanks.

[supreme Pooba]

I forgot the middle rev, but once I saw it, this was great!

[neric]

This answer is characteristic of beginners and should not be spreaded. Use the builtin mechanism as described by chepner's answer

[Hawker65]

Does this work with files with multiple extensions like image.png.gz?

[chepner]

%.* will only remove the last extension; if you want to remove all the extensions, use %%.*.

[gniourf_gniourf]

How is this different from the answer given by Steven Penny 3 years ago?

[Dale C. Anderson]

This seems to work way better than the accepted answer. It only shaves off the last extension if the file has more than one dot, whereas cut removes everything after the first dot.

[Frotz]

This one strips "tar.gz" by selecting characters before the first instance of a dot in the filename not counting the path. One probably doesn't want to strip extensions that way.

[Gabriel Staples]

How can I remove just .wiki and end up with /home/jsmith/base?

[Gabriel Staples]

Update: answer: See stackoverflow.com/a/32584935/4561887. Works perfectly!

[jpmc26]

Be warned this deletes the entire name if there is no extension and the path is relative. E.g., filename=./ihavenoextension.

[jpmc26]

Fails on ./ihavenoextension, just like the other answer.

[Y00]

be really careful if you want to use more than one dot like ./text.log

[nassim]

Thanks I was looking for some time for this. I used it to trim the last octet of an IP address echo 192.168.5.123 | cut -f -3 -d '.'

[Hibou57]

It’s even better with an -s option given to cut, so that it returns an empty string whenever the filename contains no dot.

[Tim Krief]

This should be the accepted answer in my opinion, since it works on path with dots in them, with hidden files starting with a dot, or even with file with multiple extensions.

[FedKad]

What happens when file1=/tmp.d/mainonetwosh? The sed expression should be replaced with 's/\.[^./]*$//'

[FedKad]

What happens with a file like this: file=/tmp.d/foo ?

[FedKad]

What happens with a file like this: filename=/tmp.d/foo?

[Manish Singh]

@FedonKadifeli, this works for just the file name, not for full path. But you can get the filename first using a similar approach by using / as the delimiter.

[FedKad]

It has problems with "dot files" also. Try with .profile for example.

[mwfearnley]

@Hawker65 if you know the file will have a .png.gz extension, you can use {file%.png.gz}. That will prevent it trimming after periods earlier in the file - or in the path!

[mwfearnley]

If you know it ends in .tar.gz, you can just use $(basename "$a" .tar.gz). Also, make sure to wrap your variable in quotes everywhere if there's any chance it will contain spaces or other weird characters!

[mwfearnley]

@gniourf_gniourf upvoting because you've made it a useful answer by showing how to correctly use it with a variable.

[Jinyu]

it doesn't work if filename is "a.b.c.txt'

[shaheen g]

This covers all the possibilities: stackoverflow.com/a/66177670/12969125

[shaheen g]

This covers all the possibilities: stackoverflow.com/a/66177670/12969125

[donvercety]

@FedonKadifeli use something like this: basename "$INPUT" | rev | cut -f 2- -d '.' | rev works perfectly. $INPUT is the filename or the path.

[virtualdj]

Thanks, the only answer that works with ./ihavenoextension!

[Nam G VU]

this should be the accepted answer in my view

[rivy]

@chepner, @mwfearnley, To flexibly handle dot-files, an improvement would be: (1) remove last extension => echo "$(s=${filename:1}; echo -n ${filename:0:1}; echo ${s%.*})" ; (2) remove all extensions => echo "$(s=${filename:1}; echo -n ${filename:0:1}; echo ${s%%.*})".

[jena]

@GabrielStaples you could combine it with dirname, e.g. file=/home/jsmith/base.wiki; echo $(dirname $file)/$(basename $file .wiki)

[JL Peyret]

I went with this. The nice thing is that basename is made for this and I discovered a new capability in what it can do.

[Smeterlink]

The best answer so far!

[Ravi OpenSource]

this worked for me