Command-Line Flags with Go-Lang

Kassim Damilola A — Sun, 03 Nov 2019 22:11:54 +0000

Command-line flags are a common way to specify options for command-line exercutables or programs.

Go provides a flag package supporting basic command-line flag parsing.

Flags are defined using flag.String(), Bool(), Int(), etc. Depending on the intended datatype.

First argument — Flag name
Second argument — Default value
Third argument — help message for flag nameinstances := flag.Int(“instances”, 5, “number of deployed instance”)

After all flags are defined, call




to parse the command line into the defined flags.

Command line flag syntax

The following forms are permitted:

-flag
-flag=x
-flag x // non-boolean flags only




![Alt Text](https://thepracticaldev.s3.amazonaws.com/i/tg31fio6y47bkuaft2vs.png)

$ go build flags.go

./flag -h
-instances int
number of deployed instances (default 5)

$ ./flags -instances 7

Passing CLI arguments to excutables with 'go run'

Kassim Damilola A — Sat, 02 Nov 2019 23:43:51 +0000

os.Args provides access to raw command-line arguments.

Note that the first value in this slice is the path to the program, and os.Args[1:] holds the arguments to the program.

You can get individual args with normal indexing.

To experiment with command-line arguments run 'go run cli.go parameter-1 parameter 2'

[ parameter-1 parameter 2]
 parameter-1

DEV Community: Kassim Damilola A

Command-Line Flags with Go-Lang

Passing CLI arguments to excutables with 'go run'