CommandLineArgs.md

structure CommandLineArgs

A simple command-line arguments library. It handles three kinds of arguments:

• key-value pairs with keys prefixed by -
• flags, with keys prefixed by --
• positional arguments (all others)

Interface

val parseString: string -> string -> string
val parseInt: string -> int -> int
val parseReal: string -> real -> real
val parseBool: string -> bool -> bool

The functions parseXXX key default look for -<key> <value> in the command-line arguments and return <value> if it is found, or default otherwise.

For integers, the values parsed as string should be compatible with Int.fromString.

For reals, this uses Real.fromString.

For bools, the value must be either true or false.

val parseStrings: string -> string list

parseStrings key looks for every -<key> <value> in the command-line arguments and returns a list all such <value> found.

For example, if -arg a -arg b -arg c -arg d is passed at the command line, then parseStrings "arg" returns ["a", "b", "c", "d"].

val parseFlag: string -> bool

parseFlag key returns true if --<key> was passed at the command-line.

val positional: unit -> string list

positional () returns a list of "positional" arguments: those that do not begin with either - or --.

Example

Consider the following program:

structure CLA = CommandLineArgs

val a = CLA.parseInt "a" 100
val b = CLA.parseString "b" "hello"
val c = CLA.parseFlag "c"
val d = CLA.positional ()

val _ = print ("a=" ^ Int.toString a ^ "\n")
val _ = print ("b=" ^ b ^ "\n")
val _ = print ("c=" ^ (case c of true => "true" | _ => "false") ^ "\n")
val _ = print ("d=[" ^ String.concatWith "," d ^ "]\n")

Here are a few invocations of it:

$ ./test
a=100
b=hello
c=false
d=[]

$ ./test -a 42 --c
a=42
b=hello
c=true
d=[]

$ ./test -a 42 yo --c whats up -b dude
a=42
b=dude
c=true
d=[yo,whats,up]