Command gofmt
Gofmt formats Go programs.
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.
Usage:
gofmt [flags] [path ...]
The flags are:
-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. -spaces Align with spaces instead of tabs. -tabindent Indent with tabs independent of -spaces. -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.
Examples
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
Bugs
The implementation of -r is a bit slow.