flag: update vlib/flag/README.md

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Delyan Angelov 2020-12-17 10:11:09 +02:00
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module flag for command-line flag parsing
- parsing flags like '--flag' or '--stuff=things' or '--things stuff'
- handles bool, int, float and string args
- is able to print usage
- handled unknown arguments as error
The `flag` module helps command-line flag parsing.
Main features are:
- parses flags like `-f` or '--flag' or '--stuff=things' or '--things stuff'.
- handles bool, int, float and string args.
- can print usage information listing all the declrared flags.
- handles unknown arguments as error.
Usage example:
```v
module main
```v
module main
import os
import flag
import os
import flag
fn main() {
mut fp := flag.new_flag_parser(os.args)
fp.application('flag_example_tool')
fp.version('v0.0.0')
fp.description('This tool is only designed to show how the flag lib is working')
fp.skip_executable()
an_int := fp.int('an_int', 0, 0o666, 'some int to define 0o666 is default')
a_bool := fp.bool('a_bool', 0, false, 'some \'real\' flag')
a_float := fp.float('a_float', 0, 1.0, 'also floats')
a_string := fp.string('a_string', `a`, 'no text', 'finally, some text with "a" an abbreviation')
additional_args := fp.finalize() or {
eprintln(err)
println(fp.usage())
return
}
println('
an_int: $an_int
a_bool: $a_bool
a_float: $a_float
a_string: \'$a_string\'
')
println(additional_args.join_lines())
}
```
fn main() {
mut fp := flag.new_flag_parser(os.args)
fp.application('flag_example_tool')
fp.version('v0.0.0')
fp.description('This tool is only designed to show how the flag lib is working')
fp.skip_executable()
an_int := fp.int('an_int', 0, 0o123, 'some int to define 0o123 is its default value')
a_bool := fp.bool('a_bool', 0, false, 'some boolean flag. --a_bool will set it to true.')
a_float := fp.float('a_float', 0, 1.0, 'some floating point value, by default 1.0 .')
a_string := fp.string('a_string', `a`, 'no text', 'finally, some text with ' +
' `-a` as an abbreviation, so you can pass --a_string abc or just -a abc')
additional_args := fp.finalize() or {
eprintln(err)
println(fp.usage())
return
}
println('an_int: $an_int | a_bool: $a_bool | a_float: $a_float | a_string: "$a_string" ')
println(additional_args.join_lines())
}
```