Parsing Unstructed Option Value String

In using a Tcl script as a command line call, being able to parse the argument passed to the script is vital. The following snippet shows how to retrieve and assign such values.

line 2

line 3

 

# list of tested options
set opts "-a -b -c -d -e"

##
# parse a string of arguments
##
# arguments:
#    opts    - list of options not in dict format
#    args    - list of options-values to be parsed
# returns:
#    tagged list of option/values pairs as dict
#
proc parse {opts args} {

    set i 0
    foreach item $args {
        if { $item in $opts } { 
            set tmp [string trim $item -]
            incr i
        } else {
            lappend opt($tmp) $item
        }        
    }

    if { $i != [array size opt] } { 
        error -errorinfo "Error: unbalanced list in arguments."
    }

    return [array get opt]
}

The following line will result in an error as no value passed for option -e. The list element -5 will not be mistaken for an option as it is not a member of the valid options list.

parse $opts -a {1 2 3} -b a b c -c 4 -3 -d -5 -e 

In the above example option -a receives a braced list, that is its contents is a single member of a list. The following line is balanced:

parse $opts -a {1 2 3} -b a b c -c 4 -3 -d -5 -e f

After stripping initial dashes, the following tagged list is returned 

d -5 e f a {{1 2 3}} b {a b c} c {4 -3}


The unsorted ordering being the result of maintaining values in the parse procedure as an array, In practice, this will have no impact of the application of the code.