Command Line Parsing

High Maintenance:

Use a "-X" convention to set state variables within the code.

Example: Code to parse this command line:

$> example.tcl -d -l /tmp/logging -o

  for {set i 0} {$i < [llength $argv]} {incr i} {
    switch -- [llindex $argv $i] {
      -d 	{ set debug 1 }
      -l	{ incr i; set logfile [lindex $argv $i] }
      -o        { set optimize 1; }
      default   { puts "Unrecognized argument: [lindex $argv $i]" }
      }
    }

Advantage:

• Similar to command line parsing routines used in shell or "C" programming.

Disadvantage:

• Requires code modification whenever new command line arguments are added.

Use a "-varName Value" convention to set variables within the code.

Example: Code to parse this command line:

example.tcl -debug 1 -logfile /tmp/logging -optimize 1

   for {set i 0} {$i < [llength $argv]} {incr i} {
     set arg [lindex $argv $i]
     if {[string first "-" $arg] == 0} {
       incr i;
       eval [list set [string range $arg 1 end] [lindex $argv $i]]
     } else {
       puts "Bad argument: $arg"
     }
   }

Advantage:

• New state variables can be added with no command line parsing code change.

Disadvantage:

• Command lines become long if many tuneable parameters need to be set.

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