How to highlight Bash scripts in Vim?

The answers so far are correct that you can use the extension (like .sh) or a shebang line (like #!/bin/bash) to identify the file type. If you don't have one of those, you can still specify the file type manually by using a modeline comment at the top or bottom of your file.

For instance, if you want to identify a script without an extension as a shell script, you could add this comment to the top of your file:

# vim: set filetype=sh :

or

# vim: filetype=sh

That will tell vim to treat the file as a shell script. (You can set other things in the modeline, too. In vim type :help modeline for more info.)

Actually syntax highlighting is a feature of vim not vi. Try using vim command and then do

:syntax on.

I came to this answer looking for specifically how to highlight bash syntax, not POSIX shell. Simply doing a set ft=sh (or equivalent) will result in the file being highlighted for POSIX shell, which leaves a lot of syntax that's valid in bash highlighted in red. To get bash highlighting:

" Set a variable on the buffer that tells the sh syntax highlighter
" that this is bash:
let b:is_bash = 1
" Set the filetype to sh
set ft=sh

Note that if your ft is already sh, you still need the set command; otherwise the let doesn't take effect immediately.

You can make this a global default by making the variable global, i.e., let g:is_bash = 1.

:help ft-sh-syntax is the manual page I had to find; it explains this, and how to trigger highlighting of other flavors of shell.

Vim can also detect file types by inspecting their contents (like for example if the first line contains a bash shebang), here is a quote from filetype.txt help file:

If your filetype can only be detected by inspecting the contents of the file

Create your user runtime directory. You would normally use the first item of the 'runtimepath' option. Example for Unix:

:!mkdir ~/.vim

Create a vim script file for doing this. Example:

if did_filetype()   " filetype already set..
    finish      " ..don't do these checks
endif
if getline(1) =~ '^#!.*\<mine\>'
    setfiletype mine
elseif getline(1) =~? '\<drawing\>'
    setfiletype drawing
endif

See $VIMRUNTIME/scripts.vim for more examples. Write this file as "scripts.vim" in your user runtime directory. For example, for Unix:

:w ~/.vim/scripts.vim

The detection will work right away, no need to restart Vim.

Your scripts.vim is loaded before the default checks for file types, which means that your rules override the default rules in $VIMRUNTIME/scripts.vim.

Vim can detect the file type reading the first line. Add the following line as first line.

#!/bin/sh

For those who have a variant of this question i.e. how to enable syntax highlighting on bash files without .sh extension automatically when opened...

Add filetype on in your .vimrc. This enables file type detection by also considering the file's contents. For example, bash scripts will be set to sh file-type. However, typing the #! won't trigger file type detection on a new file created with vim and you will need to use set ft=sh in that case. For more info, type :h filetype in vim.

As mentioned in the comments, you will need to use this in conjuction with syntax enable to turn on highlighting.

Or you could use :filetype detect. From the doc:

Use this if you started with an empty file and typed text that makes it possible to detect the file type. For example, when you entered this in a shell script: "#!/bin/csh".

Once you add the shebang at the top of the file, save it and reload it (e.g. :w|e) and syntax coloring can kick in.

See also Vim inconsistently syntax highlighting bash files, the accepted answer may help as well.

To toggle syntax highlight on/off while you're inside the editor.

Turn on

:syntax on

Turn off

:syntax off

Run this to always have syntax highlighting on when opening vim.

echo ":syntax on" >> ~/.vimrc

vim already recognizes many file types by default. Most of them work by file extensions, but in a case like this, vim will also analyze the content of the file to guess the correct type.

vim sets the filetype for specific file names like .bashrc, .tcshrc, etc. automatically. But a file with a .sh extension will be recognized as either csh, ksh or bash script. To determine what kind of script this is exactly, vim reads the first line of the file to look at the #! line.

If the first line contains the word bash, the file is identified as a bash script. Usually you see #!/bin/bash if the script is meant to be executed directly, but for a shell configuration file using a simple # bash would work as well.

If you want to look at the details, this is implemented in $VIMRUNTIME/filetype.vim.

Probably the easiest way to get syntax highlighting on a new file, is to just reload it after writing the shebang line. A simple :w :e will write out the file, reload it, and interprete the shebang line you have just written to provide you with the appropriate syntax highlighting.

If you already know the file-type before opening the script or if you're creating a new script without an extension which is common, you can pass it to vim on the command-line like so:

vim -c 'setfiletype sh' path/to/script
vim -c 'setfiletype python' path/to/script

When you create a new file, only the filename detection comes into play; content detection (#!/bin/bash) doesn't apply if you type it after creating a new buffer.

The sensible thing is to just do :set ft=bash the first time around, and the next time you edit it, the #!/bin/bash will set the right filetype automatically.