How can I autoformat/indent C code in vim?

Question

When I copy code from another file, the formatting is messed up, like this:

fun()
{
for(...)
{
for(...)
{
if(...)
{
}
}
}
}

How can I autoformat this code in vim?

Solution 1

Try the following keystrokes:

gg=G

Explanation: gg goes to the top of the file, = is a command to fix the indentation and G tells it to perform the operation to the end of the file.

Solution 2

I like to use the program Artistic Style. According to their website:

Artistic Style is a source code indenter, formatter, and beautifier for the C, C++, C# and Java programming languages.

It runs in Window, Linux and Mac. It will do things like indenting, replacing tabs with spaces or vice-versa, putting spaces around operations however you like (converting if(x<2) to if ( x<2 ) if that's how you like it), putting braces on the same line as function definitions, or moving them to the line below, etc. All the options are controlled by command line parameters.

In order to use it in vim, just set the formatprg option to it, and then use the gq command. So, for example, I have in my .vimrc:

autocmd BufNewFile,BufRead *.cpp set formatprg=astyle\ -T4pb

so that whenever I open a .cpp file, formatprg is set with the options I like. Then, I can type gg to go to the top of the file, and gqG to format the entire file according to my standards. If I only need to reformat a single function, I can go to the top of the function, then type gq][ and it will reformat just that function.

The options I have for astyle, -T4pb, are just my preferences. You can look through their docs, and change the options to have it format the code however you like.

Here's a demo. Before astyle:

int main(){if(x<2){x=3;}}

float test()
{
if(x<2)
x=3;
}

After astyle (gggqG):

int main()
{
    if (x < 2)
    {
        x = 3;
    }
}

float test()
{
    if (x < 2)
        x = 3;
}

Hope that helps.

Solution 3

The builtin command for properly indenting the code has already been mentioned (gg=G). If you want to beautify the code, you'll need to use an external application like indent. Since % denotes the current file in ex mode, you can use it like this:

:!indent %

Solution 4

I find that clang-format works well.

There are some example keybindings in the clang documentation

I prefer to use the equalprg binding in vim. This allows you to invoke clang-format with G=gg or other = indent options.

Just put the following in your .vimrc file:

autocmd FileType c,cpp setlocal equalprg=clang-format

Solution 5

The plugin vim-autoformat lets you format your buffer (or buffer selections) with a single command: https://github.com/vim-autoformat/vim-autoformat. It uses external format programs for that, with a fallback to vim's indentation functionality.

View more solutions

Comments

[Derek]

For anyone looking to format and not just indent the code, the second answer (mine) addresses that. If you just want to fix indenting, the accepted answer is the simplest way.

[N 1.1]

this only indents the code. can something not be done to AUTOFORMAT the entire thing?

[Lazer]

@Ton van: See my answer for the difference (Could not have explained here in comments).

[derGral]

Is there anything like this for other formats; ruby, xml, json, etc.?

[chtenb]

@Ryan check vim-autoformat, see answer below. BTW vim-autoformat also uses astyle among others.

[oligofren]

-1 This only fixes indentation, not formatting (which was what being asked for).

[Amir Rachum]

@oligofren The OP's example only included indentation errors and he accepts the answer, so I guess that's what he meant.

[Amir Rachum]

@oligofren Also, he specified he copies the code from another file, which makes indentation problems more likely than other formatting problems.

[xor007]

Suggested edit: change title to "Auto indent C code in Vim" otherwise, some people (like me) find this answer while looking for the AStyle answer.

[Frank A.]

Great, clear explanation. I will be using this command often.

[jmmk]

I haven't known such combination. I used == for single line, but I thought that = works only in visual mode,

[user3640967]

Thank you! I was beginning to think I was the only person in the word who didn't want their opening brackets on the same line as the function declaration!

[domi91c]

You can then hit <C-o><C-O> to go back to where you were.

[mellow-yellow]

In "Ex mode" (which you typically enter with :), the equivalent is :%normal == (where % means all lines in the current buffer--aka file in vim's memory--and == means autoindent the current line). This approach allows you to limit auto-indent by line number, like :5,10normal == (meaning, lines 5-10). And you can abbreviate normal to norm to save typing, as well eliminate the space: :%norm==.

[Eric]

Need to install it first, e.g for ubuntu 16.04+: sudo apt install clang-format

[a'r]

I use :set paste! for this, which toggles the paste value instead of setting it. This makes it easier to turn off as you can simply scroll back a few commands and press enter.

[71GA]

This GNU tool sucks is weird... I did not like it!

[user26742873]

Warning for readers: this set tabstop to 8. Try astyle.

[Amir Rachum]

@asuka you can set tabstop=4.

[Roel Van de Paar]

Before using this command, ensure to do sudo apt install indent to install the indent utility.