Source file src/go/build/doc.go
1 // Copyright 2011 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 // Package build gathers information about Go packages. 6 // 7 // # Go Path 8 // 9 // The Go path is a list of directory trees containing Go source code. 10 // It is consulted to resolve imports that cannot be found in the standard 11 // Go tree. The default path is the value of the GOPATH environment 12 // variable, interpreted as a path list appropriate to the operating system 13 // (on Unix, the variable is a colon-separated string; 14 // on Windows, a semicolon-separated string; 15 // on Plan 9, a list). 16 // 17 // Each directory listed in the Go path must have a prescribed structure: 18 // 19 // The src/ directory holds source code. The path below 'src' determines 20 // the import path or executable name. 21 // 22 // The pkg/ directory holds installed package objects. 23 // As in the Go tree, each target operating system and 24 // architecture pair has its own subdirectory of pkg 25 // (pkg/GOOS_GOARCH). 26 // 27 // If DIR is a directory listed in the Go path, a package with 28 // source in DIR/src/foo/bar can be imported as "foo/bar" and 29 // has its compiled form installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a" 30 // (or, for gccgo, "DIR/pkg/gccgo/foo/libbar.a"). 31 // 32 // The bin/ directory holds compiled commands. 33 // Each command is named for its source directory, but only 34 // using the final element, not the entire path. That is, the 35 // command with source in DIR/src/foo/quux is installed into 36 // DIR/bin/quux, not DIR/bin/foo/quux. The foo/ is stripped 37 // so that you can add DIR/bin to your PATH to get at the 38 // installed commands. 39 // 40 // Here's an example directory layout: 41 // 42 // GOPATH=/home/user/gocode 43 // 44 // /home/user/gocode/ 45 // src/ 46 // foo/ 47 // bar/ (go code in package bar) 48 // x.go 49 // quux/ (go code in package main) 50 // y.go 51 // bin/ 52 // quux (installed command) 53 // pkg/ 54 // linux_amd64/ 55 // foo/ 56 // bar.a (installed package object) 57 // 58 // # Build Constraints 59 // 60 // A build constraint, also known as a build tag, is a condition under which a 61 // file should be included in the package. Build constraints are given by a 62 // line comment that begins 63 // 64 // //go:build 65 // 66 // Build constraints may also be part of a file's name 67 // (for example, source_windows.go will only be included if the target 68 // operating system is windows). 69 // 70 // See 'go help buildconstraint' 71 // (https://golang.org/cmd/go/#hdr-Build_constraints) for details. 72 // 73 // # Binary-Only Packages 74 // 75 // In Go 1.12 and earlier, it was possible to distribute packages in binary 76 // form without including the source code used for compiling the package. 77 // The package was distributed with a source file not excluded by build 78 // constraints and containing a "//go:binary-only-package" comment. Like a 79 // build constraint, this comment appeared at the top of a file, preceded 80 // only by blank lines and other line comments and with a blank line 81 // following the comment, to separate it from the package documentation. 82 // Unlike build constraints, this comment is only recognized in non-test 83 // Go source files. 84 // 85 // The minimal source code for a binary-only package was therefore: 86 // 87 // //go:binary-only-package 88 // 89 // package mypkg 90 // 91 // The source code could include additional Go code. That code was never 92 // compiled but would be processed by tools like godoc and might be useful 93 // as end-user documentation. 94 // 95 // "go build" and other commands no longer support binary-only-packages. 96 // [Import] and [ImportDir] will still set the BinaryOnly flag in packages 97 // containing these comments for use in tools and error messages. 98 package build 99