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Define Function Arguments (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

• Reserved Variables: Special variables reserved by Murex

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This document was generated from builtins/core/management/shell_doc.yaml.