Documentation
¶
Overview ¶
Package flag provides a simple API for defining and parsing command-line flags in Go applications.
It is built on top of the pflag library and includes support for a set of common default flags.
Default flags:
- `--path` (string): Sets the application data path (default: OS-specific)
- `--help` (bool): Displays the help message
- `--version` (bool): Prints the application version
- `--debug` (bool): Enables debug mode
The `Init` function parses all registered flags and should be called early, typically in the `main` function of the application. If the `--help` flag is set, it prints usage information and exits.
`PrintHelp` prints the usage information for all registered flags, while `PrintEnvVars` prints the corresponding environment variable names.
Additional flags can be registered using `Register`, which accepts the flag name, a pointer to the variable to populate, and a usage description. Existing flags can be overridden using `Override`, which allows changing the variable, default value, and description of an already registered flag. Flags can be removed using `Unregister`, which removes a previously registered flag from the command line. Supported types include strings, booleans, integers, unsigned integers, and floats.
Example:
package main
import (
"fmt"
"github.com/valentin-kaiser/go-core/flag"
)
var CustomFlag string
func main() {
flag.Register("custom", &CustomFlag, "A custom flag for demonstration")
// Override the default path flag
flag.Path = "/new/default/path"
flag.Override("path", &flag.Path, "Updated application working directory")
// Unregister a flag if no longer needed
flag.Unregister("custom")
flag.Init()
fmt.Println("Custom Flag Value:", CustomFlag)
fmt.Println("Path:", flag.Path)
}
Index ¶
- Variables
- func Arguments() []string
- func DataPath(service bool, appName string) string
- func DefaultDataPath() string
- func EnvVarName(name string) string
- func Init()
- func Override(name string, value interface{}, usage string)
- func PrintEnvVars()
- func PrintHelp()
- func Register(name string, value interface{}, usage string)
- func RegisterEnvVar(name, env string)
- func ServiceDataPath() string
- func Unregister(name string)
Constants ¶
This section is empty.
Variables ¶
var ( // Path is the default path for the application data Path string // Help indicates whether the help message should be printed Help bool // Version indicates whether the version information should be printed Version bool // Debug indicates whether debug mode is enabled Debug bool // Prefix is prepended to the environment variable names derived from flags. // It is set by the config package to the configuration name. Prefix string )
Functions ¶
func Arguments ¶ added in v1.6.0
func Arguments() []string
Arguments returns the non-flag command-line arguments
func DefaultDataPath ¶ added in v1.11.0
func DefaultDataPath() string
DefaultDataPath returns the OS-specific application data path for the current executable.
func EnvVarName ¶ added in v1.11.3
EnvVarName returns the environment variable name derived from a flag name
func Init ¶
func Init()
Init initializes the flags and parses them It should be called in the main package of the application
func Override ¶
Override allows changing an existing flag's variable, default value and description It panics if the flag is not already registered or if the value is not a pointer Note: The flag must not have been parsed yet for this to work properly
func PrintEnvVars ¶ added in v1.11.3
func PrintEnvVars()
PrintEnvVars prints the environment variables derived from the registered flags to standard error output
func Register ¶ added in v1.5.1
Register registers a new flag with the given name, value and usage It panics if the flag is already registered or if the value is not a pointer
func RegisterEnvVar ¶ added in v1.11.3
func RegisterEnvVar(name, env string)
RegisterEnvVar maps a flag name to the environment variable name it is read from, without the prefix. It is used by the config package, whose configuration keys do not always match the derived flag names.
func ServiceDataPath ¶ added in v1.11.0
func ServiceDataPath() string
ServiceDataPath returns the OS-specific machine-wide data path for the current executable.
func Unregister ¶ added in v1.5.1
func Unregister(name string)
Unregister removes a previously registered flag It panics if the flag is not registered or if flags have already been parsed
Types ¶
This section is empty.
Source Files