This example demos the parsing of the next argument. If found the argument is removed and parsed as encountered. A missing argument will generate an error.
It demonstrates the following szargs functions:
// New creates a new Args object based in the arguments passed. The first
// element of the arguments must be the program name.
func New(programDesc string, args []string) *Args
// NextString removes and returns the next argument from the argument list.
//
// If no arguments remain, an error is registered.
//
// Returns the next argument value as a string.
func (args *Args) NextString(name, desc string) string
// HasNext returns true if any arguments remain unabsorbed.
func (args *Args) HasNext() bool
// PushArg places the supplied argument to the end of the internal args list.
func (args *Args) PushArg(arg string)
// NextUint removes and returns the next argument from the argument list,
// parsing it as an unsigned integer.
//
// If no arguments remain, or if the value has invalid syntax or is out of
// range for a uint, an error is registered.
//
// Returns the next argument value parsed as a uint.
func (args *Args) NextUint(name, desc string) uint
// Done registers an error if there are any remaining arguments.
func (args *Args) Done()
// HasErr returns true if any errors have been encountered or registered.
func (args *Args) HasErr() bool
// Err returns any errors encountered or registered while parsing the
// arguments.
func (args *Args) Err() error
// Usage returns a usage messages representing the Args object. It is
// formatted to the lineWidth provided. A zero uses the defaultLineWidth
// while a negative value caused an effort to determine if writing to a
// terminal and if so using its width otherwise defaulting.
func (args *Args) Usage(lineWidth int) stringThe source used for this example. It simply defines a new szargs.Arg object, then defines two positional arguments (one mandatory and one optional). Finally the Done function is called to insure that no more arguments exist in the list.
cat ./main.go// Package main implements a simple example of using szargs.
//
//nolint:forbidigo // OK to print to os.Stdout.
package main
import (
"fmt"
"os"
"github.com/dancsecs/szargs"
)
func main() {
args := szargs.New(
"A simple demo of repeating a string.",
os.Args,
)
mandatory := args.NextString(
"message",
"What to repeat.",
)
if !args.HasNext() {
args.PushArg(("3")) // Default value dor optional integer.
}
optional := args.NextUint(
"[times]",
"The number of times to repeat. Defaults to 3.",
)
args.Done() // All arguments should have consumed.
if args.HasErr() {
fmt.Fprintf(os.Stderr, "Error: %v\n\n%s\n", args.Err(), args.Usage(0))
} else {
for range optional {
fmt.Println(mandatory)
}
}
}Top of Page -- Szargs Contents
go run . StringToRepeatStringToRepeat
StringToRepeat
StringToRepeat
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go run . StringToRepeat 5StringToRepeat
StringToRepeat
StringToRepeat
StringToRepeat
StringToRepeat
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go run .Error: missing argument: message
usage: next message [times]
A simple demo of repeating a string.
message
What to repeat.
[times]
The number of times to repeat. Defaults to 3.
Top of Page -- Szargs Contents
The error is generated by the args.Done() statement causing both the
error and a usage statement to be returned.
go run . stringToRepeat 5 extraUnknownArgumentError: unexpected argument: [extraUnknownArgument]
usage: next message [times]
A simple demo of repeating a string.
message
What to repeat.
[times]
The number of times to repeat. Defaults to 3.