On wikipedia, the article for .sh says:
For the .sh file extension type, see Bourne shell.
How about other unix shells?
I know that the shebang is used inside the file to indicate an interpreter for execution, but I wonder:
I would only call .sh something that is meant to be portable (and hopefully is portable).
Otherwise I think it's just better to hide the language. The careful reader will find it in the shebang line anyway. (In practice, .bash or .zsh, etc… suffixes are rarely used.)
.bash if it's meant to be sourced by another script and is only compatible with bash, etc. If it can be sourced by any bourne-compatible shell such as sh, dash, or bash, I would give it a .sh extension. If it's meant to be executed, I wouldn't put an extension.
Commented
Jan 11, 2021 at 17:19
bash and zsh but nothing else, you could just link/symlink/copy the file to both names, or put both extensions in the name).
I would say that no "good practices" for file extensions exist, strictly on a technicality: Unix/Linux/*BSD file systems don't support extensions per se. What you are calling an extension is merely a suffix of a single file name. That's different than the VM/CMS, VMS, MS-DOS and Windows file systems and OSes where a special spot in the inode-moral-equivalent is reserved for an extension.
That little rant now over, I think it's a bit silly to put a ".sh" or ".ksh" or ".bash" suffix on a shell script file name. A program is a program: no benefit exists in distinguishing what gets executed. No unix or linux or whatever kernel has decided to call an interpreter on some file just because of a file name suffix. It's all done by the #! line, or some other "magic number" sequence of bytes at the beginning of the file. In fact, deciding what to execute based on a file name "extension" is one of the factors that makes Windows a malware magnet. Look at how many Windows malware scams involve a file named "something.jpg.exe" - by default newer Windows don't show the ".exe" extension, and encourage a user to just double click on the "image". Instead of an image view running, the malware runs.
What you might think of as a straight-ahead command is often a shell script anyway. Sometimes cc has been a sh-script, firefox is an sh-script, startx is an sh-script. I don't believe there's a cognitive or organizational benefit to marking a script with a ".sh" suffix.
.sh extension, you'll have to type that .sh as part of the command name when starting it. That's the main reason why I don't like putting that extension in (same with anything having a shebang line). BTW, the problem in Windows is not the .exe prefix per se (it's trivial to make an executable named image.jpg in Linux, after all), but the fact that Windows usually hides that extension, combined with the fact that the action needed to start an executable and to open a document is exactly the same.
As one who has worked in a multitude of ?nix environments, I have had to write in a wide variety of shells. Believe it or not, across platforms, the shells are not the same. So if you maintain your personal library in multiple shells (when necessary) it is very helpful to use extensions to ID the shells. That way when you move to another platform and the shell is slightly different, you know what scripts to target for modifications. .sh .ksh .bsh .csh ...
#! at the start of the script (e.g. #!/bin/bash)?
Commented
Jul 11, 2019 at 8:06
You should not use an extension for executables, as they they are not interchangeable. Imagine that you have a shell script a.sh, then re-write in python a.py, you now have to change every program that calls you script, you have leaked implementation detail.
The whole file-name extension thing in Mircosoft's Windows is a mess: for example what could have been a.audio, b.audio, c.audio, is a.mp3, b.wav, c.ogg, and d.picture, e.picture, f.picture is d.jpeg, e.png, f.gif. Most of the time we do not care what format the audio or picture is in. We also have to spend a long time teaching new users all of the file extensions.
*.sh I just ran into is that Debian's run-parts won't run scripts with extensions, such as in /etc/cron.*/: archive.oreilly.com/pub/post/runparts_scripts_a_note_about.html
Commented
Aug 22, 2016 at 20:42
As you said it, the Unix file extensions are purely information. You just need your script to have a correct shebang and being executable.
You can either have no extension or using .sh.
I personnaly use the following conventions, regardless of the shell used (csh, tcsh, bash, sh, ...):
.sh for classic scripts, low to high grade.Shell script extensions are quite useful. For example I often write scripts that have multiple files in multiple languages (eg. bash, awk and lua) in the same directory. If I need to search for a string in only the bash files, the extension makes this very handy, to reduce false positives. Or if I want to do a line count of all my bash code for that project.
It is a pain to have to type the extension when running the program, so I also make a symlink without the extension to the main executable, to edit/run it without needing to type the extension each time. Symlinks are cheap and easy.
As others have said, the shell doesn't care about extensions. However, it does allow for quick human identification of files. I see files ending in .py or .sh and I quickly know what they (at least) should be. As Steve says, searching by file extension or doing a line count are also practical considerations.
bash script.sh(orsh, of course).