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GOFMT(1) General Commands Manual GOFMT(1)

NAME

gofmt - format Go programs

SYNOPSIS

gofmt [flags] [path ...]

DESCRIPTION

Gofmt formats Go programs. It uses tabs for indentation and blanks for alignment. Alignment assumes that an editor is using a fixed-width font.

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.

OPTIONS

Do not print reformatted sources to standard output. If a file's formatting is different than gofmt's, print diffs to standard output.
Print all (including spurious) errors.
Do not print reformatted sources to standard output. If a file's formatting is different from gofmt's, print its name to standard output.
Apply the rewrite rule to the source before reformatting.
Try to simplify code (after applying the rewrite rule, if any).
Do not print reformatted sources to standard output. If a file's formatting is different from gofmt's, overwrite it with gofmt's version. If an error occurred during overwriting, the original file is restored from an automatic backup.

Debugging support:

Write cpu profile to the specified file.

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.

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

The simplify command

When invoked with -s gofmt will make the following source transformations where possible.

    An array, slice, or map composite literal of the form:
        []T{T{}, T{}}
    will be simplified to:
        []T{{}, {}}

    A slice expression of the form:
        s[a:len(s)]
    will be simplified to:
        s[a:]

    A range of the form:
        for x, _ = range v {...}
    will be simplified to:
        for x = range v {...}

    A range of the form:
        for _ = range v {...}
    will be simplified to:
        for range v {...}

This may result in changes that are incompatible with earlier versions of Go.

AUTHOR

This manual page was written by Michael Stapelberg <stapelberg@debian.org> and is maintained by the Debian Go Compiler Team <team+go-compiler@tracker.debian.org> based on the output of 'go doc cmd/gofmt' for the Debian project (and may be used by others).

2021-09-06