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52 lines
1.7 KiB
Go
52 lines
1.7 KiB
Go
// [_Command-line flags_](http://en.wikipedia.org/wiki/Command-line_interface#Command-line_option)
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// are a common way to specify options for command-line
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// programs. For example, in `wc -l` the `-l` is a
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// command-line flag.
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package main
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// Go provides a `flag` package supporting basic
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// command-line flag parsing. We'll use this package to
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// implement our example command-line program.
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import (
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"flag"
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"fmt"
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)
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func main() {
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// Basic flag declarations are available for string,
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// integer, and boolean options. Here we declare a
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// string flag `word` with a default value `"foo"`
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// and a short description. This `flag.String` function
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// returns a string pointer (not a string value);
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// we'll see how to use this pointer below.
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wordPtr := flag.String("word", "foo", "a string")
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// This declares `numb` and `fork` flags, using a
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// similar approach to the `word` flag.
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numbPtr := flag.Int("numb", 42, "an int")
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boolPtr := flag.Bool("fork", false, "a bool")
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// It's also possible to declare an option that uses an
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// existing var declared elsewhere in the program.
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// Note that we need to pass in a pointer to the flag
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// declaration function.
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var svar string
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flag.StringVar(&svar, "svar", "bar", "a string var")
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// Once all flags are declared, call `flag.Parse()`
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// to execute the command-line parsing.
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flag.Parse()
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// Here we'll just dump out the parsed options and
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// any trailing positional arguments. Note that we
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// need to dereference the pointers with e.g. `*wordPtr`
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// to get the actual option values.
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fmt.Println("word:", *wordPtr)
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fmt.Println("numb:", *numbPtr)
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fmt.Println("fork:", *boolPtr)
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fmt.Println("svar:", svar)
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fmt.Println("tail:", flag.Args())
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}
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