.\"                                      Hey, EMACS: -*- nroff -*-
.TH GO-BUILD 1 "2021-10-15"
.\" Please adjust this date whenever revising the manpage.
.SH NAME
go-build \- compile the packages named by the import paths
.SH SYNOPSIS
.B go build
.RB [ \-o
.IR output ]
.RI [ "build flags" ]
.RI [ packages ]
.SH DESCRIPTION
Build compiles the packages named by the import paths,
along with their dependencies, but it does not install the results.
.P
If the arguments to build are a list of .go files from a single directory,
build treats them as a list of source files specifying a single package.
.P
When compiling packages, build ignores files that end in '_test.go'.
.P
When compiling a single main package, build writes
the resulting executable to an output file named after
the first source file ('go build ed.go rx.go' writes 'ed' or 'ed.exe')
or the source code directory ('go build unix/sam' writes 'sam' or 'sam.exe').
The '.exe' suffix is added when writing a Windows executable.
.P
When compiling multiple packages or a single non-main package,
build compiles the packages but discards the resulting object,
serving only as a check that the packages can be built.
.P
The \-o flag forces build to write the resulting executable or object
to the named output file or directory, instead of the default behavior described
in the last two paragraphs. If the named output is an existing directory or
ends with a slash or backslash, then any resulting executables
will be written to that directory.
.P
The \-i flag installs the packages that are dependencies of the target.
.br
The \-i flag is deprecated. Compiled packages are cached automatically.
.SH OPTIONS
The build flags are shared by the build, clean, get, install, list, run,
and test commands:
.TP
.B \-a
force rebuilding of packages that are already up-to-date.
.TP
.B \-n
print the commands but do not run them.
.TP
.BI "\-p " n
the number of programs, such as build commands or
test binaries, that can be run in parallel.
.br
The default is GOMAXPROCS, normally the number of CPUs available.
.TP
.B \-race
enable data race detection.
.br
Supported only on linux/amd64, freebsd/amd64, darwin/amd64, windows/amd64,
linux/ppc64le and linux/arm64 (only for 48-bit VMA).
.TP
.B \-msan
enable interoperation with memory sanitizer.
Supported only on linux/amd64, linux/arm64
and only with Clang/LLVM as the host C compiler.
On linux/arm64, pie build mode will be used.
.TP
.B \-v
print the names of packages as they are compiled.
.TP
.B \-work
print the name of the temporary work directory and
do not delete it when exiting.
.TP
.B \-x
print the commands.

.TP
.BI "\-asmflags '[pattern=]" "arg list" '
arguments to pass on each go tool asm invocation.
.TP
.BI \-buildmode " mode"
build mode to use. See 'go help buildmode' for more.
.TP
.BI \-compiler " name"
name of compiler to use, as in runtime.Compiler (gccgo or gc)
.TP
.BI "\-gccgoflags '" "arg list" '
arguments to pass on each gccgo compiler/linker invocation
.TP
.BI "\-gcflags '" "arg list" '
arguments to pass on each go tool compile invocation.
.TP
.BI "\-installsuffix " suffix
a suffix to use in the name of the package installation directory,
in order to keep output separate from default builds.
If using the -race flag, the install suffix is automatically set to race
or, if set explicitly, has _race appended to it. Likewise for the \-msan
flag. Using a \-buildmode option that requires non-default compile flags
has a similar effect.
.TP
.BI "\-ldflags '" "flag list" '
arguments to pass on each go tool link invocation.
.TP
.B \-linkshared
build code that will be linked against shared libraries previously
created with \-buildmode=shared.
.TP
.BI "\-mod " mode
module download mode to use: readonly, vendor, or mod.
By default, if a vendor directory is present and the go version in go.mod
is 1.14 or higher, the go command acts as if -mod=vendor were set.
Otherwise, the go command acts as if -mod=readonly were set.
See https://golang.org/ref/mod#build-commands for details.
.TP
.B \-modcacherw
leave newly-created directories in the module cache read-write
instead of making them read-only.
.TP
.BI "\-modfile " file
in module aware mode, read (and possibly write) an alternate go.mod
file instead of the one in the module root directory. A file named
"go.mod" must still be present in order to determine the module root
directory, but it is not accessed. When -modfile is specified, an
alternate go.sum file is also used: its path is derived from the
\-modfile flag by trimming the ".mod" extension and appending ".sum".
.TP
.BI "\-overlay " file
read a JSON config file that provides an overlay for build operations.
The file is a JSON struct with a single field, named 'Replace', that
maps each disk file path (a string) to its backing file path, so that
a build will run as if the disk file path exists with the contents
given by the backing file paths, or as if the disk file path does not
exist if its backing file path is empty. Support for the -overlay flag
has some limitations: importantly, cgo files included from outside the
include path must be in the same directory as the Go package they are
included from, and overlays will not appear when binaries and tests are
run through go run and go test respectively.
.TP
.BI "\-pkgdir " dir
install and load all packages from dir instead of the usual locations.
For example, when building with a non-standard configuration,
use \-pkgdir to keep generated packages in a separate location.
.TP
.BR "\-tags " tag,list
a comma-separated list of build tags to consider satisfied during the
build. For more information about build tags, see the description of
build constraints in the documentation for the go/build package.
(Earlier versions of Go used a space-separated list, and that form
is deprecated but still recognized.)
.TP
.B \-trimpath
remove all file system paths from the resulting executable.
Instead of absolute file system paths, the recorded file names
will begin with either "go" (for the standard library),
or a module path@version (when using modules),
or a plain import path (when using GOPATH).
.TP
.BI "\-toolexec '" "cmd args" '
a program to use to invoke toolchain programs like vet and asm.
For example, instead of running asm, the go command will run
\(oqcmd args /path/to/asm <arguments for asm>\(cq.
.br
The TOOLEXEC_IMPORTPATH environment variable will be set,
matching \(oqgo list -f {{.ImportPath}}\(cq for the package being built.

.P
The \-asmflags, \-gccgoflags, \-gcflags, and \-ldflags flags accept a
space-separated list of arguments to pass to an underlying tool
during the build. To embed spaces in an element in the list, surround
it with either single or double quotes. The argument list may be
preceded by a package pattern and an equal sign, which restricts
the use of that argument list to the building of packages matching
that pattern (see 'go help packages' for a description of package
patterns). Without a pattern, the argument list applies only to the
packages named on the command line. The flags may be repeated
with different patterns in order to specify different arguments for
different sets of packages. If a package matches patterns given in
multiple flags, the latest match on the command line wins.
For example, 'go build \-gcflags=-S fmt' prints the disassembly
only for package fmt, while 'go build \-gcflags=all=-S fmt'
prints the disassembly for fmt and all its dependencies.
.P
For more about specifying packages, see \fBgo-packages\fP(7).
.br
For more about where packages and binaries are installed, see \fBgo-gopath\fP(1).
.br
For more about calling between Go and C/C++, run 'go help c'.
.P
Note: Build adheres to certain conventions such as those described
by 'go help gopath'. Not all projects can follow these conventions,
however. Installations that have their own conventions or that use
a separate software build system may choose to use lower-level
invocations such as 'go tool compile' and 'go tool link' to avoid
some of the overheads and design decisions of the build tool.
.SH SEE ALSO
.BR go-install (1),
.BR go-get (1),
.BR go-clean (1).
.SH 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 help build'
for the Debian project (and may be used by others).