Richard Suchenwirth 2006-12-08 - Tcl scripts started from the command line can often be configured with switches (also called flags) like
$ myscript.tcl -v -sep ';' whatever
Here's my little take to parse out switches from the command line (argv) by name. If a variable name is given, the word following the switch is assigned to it; in any case, the flag (and possibly the consumed following word) are removed from the command line, and 1 is returned if the flag was found, else 0.
proc getopt {_argv name {_var ""} {default ""}} { upvar 1 $_argv argv $_var var set pos [lsearch -regexp $argv ^$name] if {$pos>=0} { set to $pos if {$_var ne ""} { set var [lindex $argv [incr to]] } set argv [lreplace $argv $pos $to] return 1 } else { if {[llength [info level 0]] == 5} {set var $default} return 0 } }
Larry Smith see also init.
Usage examples:
getopt argv -sep sep ";" ;# possibly override default with user preference set verbose [getopt argv -v] ;# boolean flag, no trailing word
Searching with -regexp allows to specify longer mnemonic names, so it still succeeds on longer flags, e.g.
$ myscript.tcl -separator '\t' ...
If you use this separator for joining lists, make sure to subst -nocommand it before use.
wdb In my case, I use switches always with a value such that there is always a pair key - value which I collect into an array as follows:
% proc testSwitch {arg1 args} { array set switch [concat { -accept no } $args] list arg1 was $arg1, -accept was $switch(-accept). } % testSwitch Wurst arg1 was Wurst, -accept was no. % testSwitch Kaese -accept yes arg1 was Kaese, -accept was yes. %
RS: true, named arguments can be handled simpler. What I wanted was an option extractor from command lines, which may contain different numbers of file names, etc.
escargo - Command line using is sometimes complicated by options where the order is important and where some options can occur multiple times with different meanings. Some problematic cases:
People are far to clever about how options (or arguments) ought to be interpreted.