In the last blog I talked about command line arguments os.Args[]. In this I will try and create a sample banner program that shall
- Take 3 arguments
n- Number of times a message has to be repeated.m- The message that needs to be shown.d- If debug message needs to be shown.
I am going to use the flags package.
Source code is available here
— https://github.com/samarthya
Defining: Banner#
The package flag has the extended capability of parsing the flags.
Define Flags#
Variant one#
var times = flag.Int("n", 1, "number of times the message needs to be displayed")
var msg = flag.String("m", "", "the message that needs to be printed")
var dbg = flag.Bool("d", false, "to debug or not")A good reference available here.
You can also define flags using
var nTimes int
func init() {
flag.IntVar(&nTimes, "n", 1, "number of times the message needs to be displayed")
}After all flags are defined you must call, to parse the command line into flags. If you miss this one you might not get the desired results. (Give it a try)
// Must be called after all flags are defined and before flags are accessed within the program
flag.Parse()How to pass values to these flags?
-flag
-flag=x
-flag xBuild#
go build src/cmdline/cmd.goThis will produce the binary - cmd.
Run the cmd#
./cmd
-d to debug or not
-m string
the message that needs to be printed
-n int
number of times the message needs to be displayed (default 1)./cmd -n 2 -m="Why is world round?"
--- Command line Program ---
>> Why is world round?
>> Why is world round?./cmd -n 2 -m="Why is world round?" -d=true
DBG: Number of Arguments: 5
--- Command line Program ---
>> Why is world round?
>> Why is world round?./cmd -m="Why is world round?" -n=3 -d=true
DBG: Number of Arguments: 4
--- Command line Program ---
>> Why is world round?
>> Why is world round?
>> Why is world round?