gofmt

Format a file and display the result to the console

$ gofmt [source.go]

Format a file, overwriting the original file in-place

$ gofmt -w [source.go]

Format a file, and then simplify the code, overwriting the original file

$ gofmt -s -w [source.go]

Print all (including spurious) errors

$ gofmt -e [source.go]

gofmt [flags] [ path ... ]

Without an explicit path, it processes the standard input. Given a file, it operates on that file; given a directory, it operates on all .go files in that directory, recursively. (Files starting with a period are ignored.) By default, gofmt prints the reformatted sources to standard output.

-d

Do not print reformatted sources to standard output. If a file's formatting is different than gofmt's, print diffs to standard output.

-e

Print all (including spurious) errors.

-l

Do not print reformatted sources to standard output. If a file's formatting is different from gofmt's, print its name to standard output.

-r rule

Apply the rewrite rule to the source before reformatting.

-s

Try to simplify code (after applying the rewrite rule, if any).

-w

Do not print reformatted sources to standard output. If a file's formatting is different from gofmt's, overwrite it with gofmt's version.

Formatting control flags:

-comments=true

Print comments; if false, all comments are elided from the output.

-tabs=true

Indent with tabs; if false, spaces are used instead.

-tabwidth=8

Tab width in spaces.

The rewrite rule specified with the -r flag must be a string of the form:

pattern -> replacement

Both pattern and replacement must be valid Go expressions. In the pattern, single-character lowercase identifiers serve as wildcards matching arbitrary sub-expressions; those expressions will be substituted for the same identifiers in the replacement.

When gofmt reads from standard input, it accepts either a full Go program or a program fragment. A program fragment must be a syntactically valid declaration list, statement list, or expression. When formatting such a fragment, gofmt preserves leading indentation as well as leading and trailing spaces, so that individual sections of a Go program can be formatted by piping them through gofmt.

To check files for unnecessary parentheses:

gofmt -r '(a) -> a' -l *.go

To remove the parentheses:

gofmt -r '(a) -> a' -w *.go

To convert the package tree from explicit slice upper bounds to implicit ones:

gofmt -r 'α[β:len(α)] -> α[β:]' -w $GOROOT/src/pkg

The implementation of -r is a bit slow.

This manual page was written by Michael Stapelberg <stapelberg@debian.org>, for the Debian project (and may be used by others).