README
¶
flagx 
Helper functions to use with the Go standard library flag package.
Documentation
¶
Overview ¶
Package flagx implements extensions to the standard flag package in the form of types that implement flag.Value
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func BoolFunc ¶ added in v0.22.2
BoolFunc defines a flag with the specified name and usage string. Each time the flag is set with a truthy value, fn is called. If fn returns a non-nil error, it will be treated as a flag value parsing error.
Example ¶
package main
import (
"flag"
"fmt"
"github.com/carlmjohnson/flagx"
)
func main() {
fs := flag.NewFlagSet("ExampleParseEnv", flag.PanicOnError)
flagx.BoolFunc(fs, "call-me", "", func() error {
fmt.Println("called!")
return nil
})
flagx.BoolFunc(fs, "dont-call-me", "", func() error {
fmt.Println("not called!")
return nil
})
fs.Parse([]string{"-call-me", "-dont-call-me=false"})
}
Output: called!
func Missing ¶
Missing returns a slice of required flags missing from an error returned by MustHave.
func MustHave ¶
MustHave is a convenience function that checks that the named flags were set on fl. Missing flags are treated with the policy of fl.ErrorHandling(): ExitOnError, ContinueOnError, or PanicOnError. Returned errors can be unpacked by Missing.
If nil, fl defaults to flag.CommandLine.
Example (MissingFlag) ¶
package main
import (
"flag"
"fmt"
"os"
"github.com/carlmjohnson/flagx"
)
func main() {
fs := flag.NewFlagSet("ExampleMustHave", flag.ContinueOnError)
fs.SetOutput(os.Stdout)
fs.String("a", "", "this value must be set")
fs.String("b", "", "this value must be set")
fs.String("c", "", "this value is optional")
fs.Parse([]string{"-a", "set"})
err := flagx.MustHave(fs, "a", "b")
fmt.Println("Missing:", flagx.Missing(err))
}
Output: missing required flag: b Usage of ExampleMustHave: -a string this value must be set -b string this value must be set -c string this value is optional Missing: [b]
Example (NoMissingFlag) ¶
package main
import (
"flag"
"github.com/carlmjohnson/flagx"
)
func main() {
fs := flag.NewFlagSet("ExampleMustHave", flag.PanicOnError)
fs.String("a", "", "this value must be set")
fs.String("b", "", "this value must be set")
fs.String("c", "", "this value is optional")
fs.Parse([]string{"-a", "set", "-b", "set"})
flagx.MustHave(fs, "a", "b")
}
Output:
func MustHaveArgs ¶
MustHaveArgs is a convenience function that checks that fl.NArg() is within the bounds min and max (inclusive). Use max -1 to indicate no maximum value. MustHaveArgs uses the policy of fl.ErrorHandling(): ExitOnError, ContinueOnError, or PanicOnError.
If nil, fl defaults to flag.CommandLine.
Example (CorrectNumber) ¶
package main
import (
"flag"
"github.com/carlmjohnson/flagx"
)
func main() {
fs := flag.NewFlagSet("ExampleMustHave", flag.PanicOnError)
fs.String("a", "", "an option")
fs.Parse([]string{"--", "-a", "-b", "-c"})
flagx.MustHaveArgs(fs, 3, 3)
}
Output:
Example (WrongNumber) ¶
package main
import (
"flag"
"fmt"
"strings"
"github.com/carlmjohnson/flagx"
)
func main() {
var buf strings.Builder
defer func() {
recover()
fmt.Println(buf.String())
}()
fs := flag.NewFlagSet("ExampleMustHaveArgs", flag.PanicOnError)
fs.SetOutput(&buf)
fs.Usage = func() {
fmt.Fprintf(fs.Output(), "Usage:\n\tExampleMustHaveArgs [optional arg]")
}
fs.Parse([]string{"--", "one", "two"})
flagx.MustHaveArgs(fs, 0, 1)
}
Output: must have between 0 and 1 args; got 2 Usage: ExampleMustHaveArgs [optional arg]
func ParseEnv ¶
ParseEnv lists any unset flags, checks whether a corresponding environment variable exists, and if so calls Set with its value. Flag names are prefixed and converted to SCREAMING_SNAKE_CASE when looking up environment variables.
Example ¶
package main
import (
"flag"
"fmt"
"os"
"github.com/carlmjohnson/flagx"
)
func main() {
fs := flag.NewFlagSet("ExampleParseEnv", flag.PanicOnError)
a := fs.Int("a", 0, "")
b := fs.Int("b", 0, "")
fs.Parse([]string{"-a", "1"})
os.Setenv("TEST_ENV_A", "2")
os.Setenv("TEST_ENV_B", "3")
flagx.ParseEnv(fs, "test-env")
// Does not override existing values
fmt.Println("a", *a)
// Does get new values from env
fmt.Println("b", *b)
}
Output: a 1 b 3
Types ¶
This section is empty.
Source Files
Directories