How do I rename the extension for a bunch of files?

If using bash, there's no need for external commands like sed, basename, rename, expr, etc.

for file in *.html
do
  mv "$file" "${file%.html}.txt"
done

For an better solution (with only bash functionality, as opposed to external calls), see one of the other answers.

The following would do and does not require the system to have the rename program (although you would most often have this on a system):

for file in *.html; do
    mv "$file" "$(basename "$file" .html).txt"
done

EDIT: As pointed out in the comments, this does not work for filenames with spaces in them without proper quoting (now added above). When working purely on your own files that you know do not have spaces in the filenames this will work but whenever you write something that may be reused at a later time, do not skip proper quoting.

rename 's/\.html$/\.txt/' *.html

does exactly what you want.

You want to use rename :

rename -S <old_extension> <new_extension> <files>

rename -S .html .txt *.html

This does exactly what you want - it will change the extension from .html to .txt for all files matching *.html.

Note: Greg Hewgill correctly points out this is not a bash builtin; and is a separate Linux command. If you just need something on Linux this should work fine; if you need something more cross-platform then take a look at one of the other answers.

This is the slickest solution I've found that works on OSX and Linux, and it works nicely with git too!

find . -name "*.js" -exec bash -c 'mv "$1" "${1%.js}".tsx' - '{}' \;

and with git:

find . -name "*.js" -exec bash -c 'git mv "$1" "${1%.js}".tsx' - '{}' \;

One line, no loops:

ls -1 | xargs -L 1 -I {} bash -c 'mv $1 "${1%.*}.txt"' _ {}

Example:

$ ls
60acbc4d-3a75-4090-85ad-b7d027df8145.json  ac8453e2-0d82-4d43-b80e-205edb754700.json
$ ls -1 | xargs -L 1 -I {} bash -c 'mv $1 "${1%.*}.txt"' _ {}
$ ls
60acbc4d-3a75-4090-85ad-b7d027df8145.txt  ac8453e2-0d82-4d43-b80e-205edb754700.txt

The command mmv seems to do this task very efficiently on a huge number of files (tens of thousands in a second). For example, to rename all .xml files to .html files, use this:

mmv ";*.xml" "#1#2.html"

the ; will match the path, the * will match the filename, and these are referred to as #1 and #2 in the replacement name.

Answers based on exec or pipes were either too slow or failed on a very large number of files.

This is a good way to modify multiple extensions at once:

for fname in *.{mp4,avi}
do
   mv -v "$fname" "${fname%.???}.mkv"
done

Note: be careful at the extension size to be the same (the ???)

In Linux or window git bash or window's wsl, try below command to change every file's extension in current directory or sub-directories or even their sub-directories with just one line of code

find . -depth -name "*.html" -exec sh -c 'mv "$1" "${1%.html}.txt"' _ {} \;

Rename file extensions for all files under current directory and sub directories without any other packages (only use shell script):

1. Create a shell script rename.sh under current directory with the following code:

   #!/bin/bash
   
   for file in $(find . -name "*$1"); do
     mv "$file" "${file%$1}$2"
   done
   

2. Run it by ./rename.sh .old .new.

   Eg. ./rename.sh .html .txt

Similarly to what was suggested before, this is how I did it:

find . -name '*OldText*' -exec sh -c 'mv "$0" "${0/OldText/NewText}"' {} \;

I first validated with

find . -name '*OldText*' -exec sh -c 'echo mv "$0" "${0/OldText/NewText}"' {} \;

Nice & simple!

find . -iname *.html  -exec mv {} "$(basename {} .html).text"  \;

Here is what i used to rename .edge files to .blade.php

for file in *.edge; do     mv "$file" "$(basename "$file" .edge).blade.php"; done

Works like charm.

You can also make a function in Bash, add it to .bashrc or something and then use it wherever you want.

change-ext() {
    for file in *.$1; do mv "$file" "$(basename "$file" .$1).$2"; done
}

Usage:

change-ext css scss

Source of code in function: https://stackoverflow.com/a/1224786/6732111

The easiest way is to use rename.ul it is present in most of the Linux distro

rename.ul -o -v [oldFileExtension] [newFileExtension] [expression to search for file to be applied with]

rename.ul -o -v .oldext .newext *.oldext

Options:

-o: don't overwrite preexisting .newext

-v: verbose

-n: dry run

Unfortunately it's not trivial to do portably. You probably need a bit of expr magic.

for file in *.html; do echo mv -- "$file" "$(expr "$file" : '\(.*\)\.html').txt"; done

Remove the echo once you're happy it does what you want.

Edit: basename is probably a little more readable for this particular case, although expr is more flexible in general.

Here is a solution, using AWK. Make sure the files are present in the working directory. Else, cd to the directory where the html files are located and then execute the below command:

for i in $(ls | grep .html); do j=$(echo $i | grep -oh "^\w*." | awk '{print $1"txt"}'); mv $i $j; done

I wrote this code in my .bashrc

alias find-ext='read -p "Path (dot for current): " p_path; read -p "Ext (unpunctured): " p_ext1; find $p_path -type f -name "*."$p_ext1'
alias rename-ext='read -p "Path (dot for current): " p_path; read -p "Ext (unpunctured): " p_ext1; read -p "Change by ext. (unpunctured): " p_ext2; echo -en "\nFound files:\n"; find $p_path -type f -name "*.$p_ext1"; find $p_path -type f -name "*.$p_ext1" -exec sh -c '\''mv "$1" "${1%.'\''$p_ext1'\''}.'\''$p_ext2'\''" '\'' _ {} \;; echo -en "\nChanged Files:\n"; find $p_path -type f -name "*.$p_ext2";'

In a folder like "/home/<user>/example-files" having this structure:

• /home/<user>/example-files:
  • file1.txt
  • file2.txt
  • file3.pdf
  • file4.csv

The commands would behave like this:

~$ find-text
Path (dot for current): example-files/
Ext (unpunctured): txt

example-files/file1.txt
example-files/file2.txt


~$ rename-text
Path (dot for current): ./example-files
Ext (unpunctured): txt
Change by ext. (unpunctured): mp3

Found files:
./example-files/file1.txt
./example-files/file1.txt

Changed Files:
./example-files/file1.mp3
./example-files/file1.mp3
~$

You could use a tool designed for renaming files in bulk, e.g. renamer.

To rename all file extensions in the current folder:

$ renamer --find ".html" --replace ".txt" --dry-run * 

Many more usage examples here.