diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
commit | 43a123c1ae6613b3efeed291fa552ecd909d3acf (patch) | |
tree | fd92518b7024bc74031f78a1cf9e454b65e73665 /src/flag/example_test.go | |
parent | Initial commit. (diff) | |
download | golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip |
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/flag/example_test.go')
-rw-r--r-- | src/flag/example_test.go | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/src/flag/example_test.go b/src/flag/example_test.go new file mode 100644 index 0000000..088447d --- /dev/null +++ b/src/flag/example_test.go @@ -0,0 +1,85 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// These examples demonstrate more intricate uses of the flag package. +package flag_test + +import ( + "errors" + "flag" + "fmt" + "strings" + "time" +) + +// Example 1: A single string flag called "species" with default value "gopher". +var species = flag.String("species", "gopher", "the species we are studying") + +// Example 2: Two flags sharing a variable, so we can have a shorthand. +// The order of initialization is undefined, so make sure both use the +// same default value. They must be set up with an init function. +var gopherType string + +func init() { + const ( + defaultGopher = "pocket" + usage = "the variety of gopher" + ) + flag.StringVar(&gopherType, "gopher_type", defaultGopher, usage) + flag.StringVar(&gopherType, "g", defaultGopher, usage+" (shorthand)") +} + +// Example 3: A user-defined flag type, a slice of durations. +type interval []time.Duration + +// String is the method to format the flag's value, part of the flag.Value interface. +// The String method's output will be used in diagnostics. +func (i *interval) String() string { + return fmt.Sprint(*i) +} + +// Set is the method to set the flag value, part of the flag.Value interface. +// Set's argument is a string to be parsed to set the flag. +// It's a comma-separated list, so we split it. +func (i *interval) Set(value string) error { + // If we wanted to allow the flag to be set multiple times, + // accumulating values, we would delete this if statement. + // That would permit usages such as + // -deltaT 10s -deltaT 15s + // and other combinations. + if len(*i) > 0 { + return errors.New("interval flag already set") + } + for _, dt := range strings.Split(value, ",") { + duration, err := time.ParseDuration(dt) + if err != nil { + return err + } + *i = append(*i, duration) + } + return nil +} + +// Define a flag to accumulate durations. Because it has a special type, +// we need to use the Var function and therefore create the flag during +// init. + +var intervalFlag interval + +func init() { + // Tie the command-line flag to the intervalFlag variable and + // set a usage message. + flag.Var(&intervalFlag, "deltaT", "comma-separated list of intervals to use between events") +} + +func Example() { + // All the interesting pieces are with the variables declared above, but + // to enable the flag package to see the flags defined there, one must + // execute, typically at the start of main (not init!): + // flag.Parse() + // We don't call it here because this code is a function called "Example" + // that is part of the testing suite for the package, which has already + // parsed the flags. When viewed at pkg.go.dev, however, the function is + // renamed to "main" and it could be run as a standalone example. +} |