murex Shell Docs

Command Reference: args

Command line flag parser for murex shell scripting

Description

One of the nuisances of shell scripts is handling flags. More often than not your script will be littered with $1 still variables and not handle flags shifting in placement amongst a group of parameters. args aims to fix that by providing a common tool for parsing flags.

args takes a name of a variable to assign the result of the parsed parameters as well as a JSON structure containing the result. It also returns a non-zero exit number if there is an error when parsing.

Usage

args var-name { json-block } -> <stdout>

Examples

#!/usr/bin/env murex

# First we define what parameters to accept:
# Pass the `args` function a JSON string (because JSON objects share the same braces as murex block, you can enter JSON
# directly as unescaped values as parameters in murex).
#
# --str: str == string data type
# --num: num == numeric data type
# --bool: bool == flag used == true, missing == false
# -b: --bool == alias of --bool flag
args: args {
    "AllowAdditional": true,
    "Flags": {
        "--str": "str",
        "--num": "num",
        "--bool": "bool",
        "-b": "--bool"
    }
}
catch {
    # Lets check for errors in the command line parameters. If they exist then
    # print the error and then exit.
    err $args[Error]
    exit 1
}

out "The structure of \$args is: ${$args->pretty}\n\n"


# Some example usage:
# -------------------

!if { $args->[[ /Flags/--bool ]] } {
    out "Flag `--bool` was not set."
}

# `<!null>` redirects the STDERR to a named pipe. In this instance it's the 'null' pipe so equivalent to 2>/dev/null
# thus we are just suppressing any error messages.
try <!null> {
    $args -> [[ /Flags/--str ]] -> set fStr
    $args -> [[ /Flags/--num ]] -> set fNum

    out "Defined Flags:"
    out "  --str == $fStr"
    out "  --num == $fNum"
}

catch {
    err "Missing `--str` and/or `--num` flags."
}

$args -> [ Additional ] -> foreach flag {
    out "Additional argument (ie not assigned to a flag): `$flag`."
}

See Also

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Last built on Fri Sep 10 15:05:25 UTC 2021 against commit 437c274437c274fded54d82e99d70ea7d2917f332c095dd.

Current version is 2.2.1200 BETA which has been verified against tests.