What is the difference between gofmt & go fmt?

Question

I see that there is both gofmt and go fmt. What is the difference between gofmt & go fmt?

Answer 1

Run go help fmt to see the difference. In short, go fmt runs gofmt -l -w on the packages specified by the arguments.

The -w flag writes the result back to the source file. The -l flag prints the name of modified files.

The arguments to go fmt are packages (run go help packages for a description). The arguments to gofmt are file system paths.

Here are some examples showing how the arguments are handled differently:

 gofmt -w .   # formats files in current directory and all sub-directories
 go fmt ./... # similar to previous
 go fmt .     # formats files in current package
 gofmt -w foo/bar # formats files in directory $PWD/foo/bar and sub-dirs
 go fmt foo/bar   # formats files in directory $GOPATH/src/foo/bar
 gofmt -w     # error, no file or directory specified
 go fmt       # formats files in current package

Answer 2

The gofmt command will process the files given as arguments. The go fmt tool runs gofmt on all the files in the package paths given as arguments. Thus if I am in the encoding/gob directory,

gofmt decode.go

will format the single file decode.go, while the tool run

go fmt .

(. is actually the default) will format all the files in the encoding/gob package.