WJG (25nd May, 2005) I expect that something like this code snippet is already somewhere on the Wiki but I thought it worth a posting as this method allows for cleaner, simpler code.
Larry Smith This is precisely what init does, but init also provides a way to initialize switches, and will disallow setting things that the proc isn't able to understand (this is both a security thing as well as error detection). init can also parse your argv as well, if called in the global scope.
If a proceedure has a whole range of switches then why waste time parsing the args list with a load of switch options or if.. else.. constructions? Just assume that the switch names themselves have some meaningful description within the scope of the calling proc, strip out the leading "-" and use the remnamt of the string as a variable name.
As the proc documentation should always contain some explanation of the usage of the proceedure, its arguments and switches should be no cause for confusion.
# -------------------------------------------------------
# proc:
# easyargs -just a piece of demo code
#
# args:
# a
# b
#
# switches:
# -up
# -down
# -in
# -out
#
# -------------------------------------------------------
proc easyargs {a b args} {
# read in args, set values according to switch names
foreach {opt val} $args {
set tmp [string trim $opt -]
set $tmp $val
}
#just to prove that the values are set...
foreach item {up down in out} {
puts "$item [set $item]"
}
}
easyargs red green -up 0 -down 1 -in 0 -out 1WJG (16/12/11) I thought that I'd revisit this task but allow for the setting of defaults and some error checking. The above is fine, but I don't want to have such a bulky solution. Much better to have a single proc to call to handle the necessaries.
#---------------
# parse options string and set values within scope of calling procedure
#---------------
# Arguments
# options array containing procedure option names and default values
# args list of options and values passed to calling procedure
# Returns
# 0 if successful or -1 if there is an error.
#
# Notes
# The function creates variables within the scope of the calling function
# by stripping away the leading "-" and using a variable name derived from
# shifting the option string to lowercase.
#
# If an undefined option is specified, the error will be reported to stderr
# and the script will terminate.
#
# Following the creation of the variables, the options array will be unset.
#
proc parseOptions {options args} {
upvar $options opts
set names [array names opts]
# set default values for the options
foreach item $names {
set aa [string tolower [string trimleft $item -]]
uplevel 1 set $aa $opts($item)
}
# change option values to those specified in args
foreach {a b} [lindex $args 0] {
if { [string first $a $names] >= 0 } {
set aa [string tolower [string trimleft $a -]]
uplevel 1 set $aa [list $b]
} else {
set err "ERROR! Invalid option $a, should be one of [array names opts]."
exit -1
}
}
# clear the options array
uplevel 1 unset opts
}
proc testProc1 {val args} {
# set options and default values
array set opts {-opt1 A -opt2 B -opt3 C -opt4 ZZZZZ}
puts [parray opts]
parseOptions opts $args
foreach i [info vars] { puts "$i = [set $i]" }
if { [catch {puts [parray opts] }] } { puts "Array opts no longer exists" }
}
proc testProc2 {val args} {
# set options and default values
array set opts {-Day A -Day B -Month C -Year D }
parseOptions opts $args
foreach i [info vars] { puts "$i = [set $i]" }
puts "Happy Yuletide: $day $month $year"
}
testProc1 25-DEC -opt1 "HAPPY NEW YEAR" -opt2 "Merry Christmas" -opt3 "MERRY YULETIDE"
testProc2 25-DEC -Day 25th -Month December -Year 2011See also Named arguments