github.com/bgentry/go@v0.0.0-20150121062915-6cf5a733d54d/src/cmd/gofmt/doc.go (about) 1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 /* 6 Gofmt formats Go programs. 7 It uses tabs (width = 8) for indentation and blanks for alignment. 8 9 Without an explicit path, it processes the standard input. Given a file, 10 it operates on that file; given a directory, it operates on all .go files in 11 that directory, recursively. (Files starting with a period are ignored.) 12 By default, gofmt prints the reformatted sources to standard output. 13 14 Usage: 15 gofmt [flags] [path ...] 16 17 The flags are: 18 -d 19 Do not print reformatted sources to standard output. 20 If a file's formatting is different than gofmt's, print diffs 21 to standard output. 22 -e 23 Print all (including spurious) errors. 24 -l 25 Do not print reformatted sources to standard output. 26 If a file's formatting is different from gofmt's, print its name 27 to standard output. 28 -r rule 29 Apply the rewrite rule to the source before reformatting. 30 -s 31 Try to simplify code (after applying the rewrite rule, if any). 32 -w 33 Do not print reformatted sources to standard output. 34 If a file's formatting is different from gofmt's, overwrite it 35 with gofmt's version. 36 37 Debugging support: 38 -cpuprofile filename 39 Write cpu profile to the specified file. 40 41 42 The rewrite rule specified with the -r flag must be a string of the form: 43 44 pattern -> replacement 45 46 Both pattern and replacement must be valid Go expressions. 47 In the pattern, single-character lowercase identifiers serve as 48 wildcards matching arbitrary sub-expressions; those expressions 49 will be substituted for the same identifiers in the replacement. 50 51 When gofmt reads from standard input, it accepts either a full Go program 52 or a program fragment. A program fragment must be a syntactically 53 valid declaration list, statement list, or expression. When formatting 54 such a fragment, gofmt preserves leading indentation as well as leading 55 and trailing spaces, so that individual sections of a Go program can be 56 formatted by piping them through gofmt. 57 58 Examples 59 60 To check files for unnecessary parentheses: 61 62 gofmt -r '(a) -> a' -l *.go 63 64 To remove the parentheses: 65 66 gofmt -r '(a) -> a' -w *.go 67 68 To convert the package tree from explicit slice upper bounds to implicit ones: 69 70 gofmt -r 'α[β:len(α)] -> α[β:]' -w $GOROOT/src 71 72 The simplify command 73 74 When invoked with -s gofmt will make the following source transformations where possible. 75 76 An array, slice, or map composite literal of the form: 77 []T{T{}, T{}} 78 will be simplified to: 79 []T{{}, {}} 80 81 A slice expression of the form: 82 s[a:len(s)] 83 will be simplified to: 84 s[a:] 85 86 A range of the form: 87 for x, _ = range v {...} 88 will be simplified to: 89 for x = range v {...} 90 */ 91 package main 92 93 // BUG(rsc): The implementation of -r is a bit slow.