commit 5b9fbd58a16f02d98dbc6f0b4be7af12aa186cae
from: Sven M. Hallberg <pesco@khjk.org>
date: Sun May 25 08:14:33 2025 UTC

more getopt improvements

Set arg variable to 1 for boolean flags.

commit - 19d28f97177c183d78bbce4642857db2ea27541f
commit + 5b9fbd58a16f02d98dbc6f0b4be7af12aa186cae
blob - fcbd49da45d37f494b7475ce90749039c3ab4052
blob + 00195068734320ee5a9de3ef41853d0015f9adb1
--- exercise
+++ exercise
@@ -268,19 +268,19 @@ proc getopt {argvvar optstring optvar argvar} {
     upvar $argvvar argv $optvar opt $argvar arg
 
     set arg [lindex $argv 0]                    ;# "" if argv empty
-    set opt [string index $arg 1]               ;# "" if arg empty
+    set opt [string index $arg 1]               ;# "" if arg empty or length 1
     if {$opt eq "" || [string index $arg 0] ne "-"} {
         return 0                                ;# no option
     }
     set argv [lreplace $argv 0 0]               ;# tentative consumption
     if {$arg eq "--"} {
-        return 0                                ;# end of options
+        return 0                                ;# terminate option processing
     }
 
     # consume option character
-    set arg [string replace $arg 1 1]
-    if {$arg ne "-"} {                          ;# not yet exhausted?
-        set argv [linsert $argv 0 $arg]         ;# put it back for now
+    set arg [string replace $arg 0 1]           ;# cut off the dash, too
+    if {$arg ne ""} {                           ;# not yet exhausted?
+        set argv [linsert $argv 0 -$arg]        ;# put it back for now
     }
 
     # check if option is valid
@@ -288,20 +288,21 @@ proc getopt {argvvar optstring optvar argvar} {
     if {$idx == -1 || $opt eq ":"} {
         puts stderr "[file tail $::argv0]: unknown option -$opt"
         set opt "?"
-        return 1                                ;# could come back for more
+        return 1                                ;# can call again for more
     }
 
     # handle option arguments
-    if {[string index $optstring [expr $idx + 1]] eq ":"} {
-        if {$arg ne "-"} {
-            set arg [string range $arg 1 end]   ;# use the rest of arg
-        } elseif {[llength $argv] > 0} {
-            set arg [lindex $argv 0]            ;# use the next arg
-        } else {
-            puts stderr "[file tail $::argv0]: -$opt requires an argument"
-            set opt [expr {[string index $optstring 0] eq ":" ? ":" : "?"}]
+    if {[string index $optstring [incr idx]] eq ":"} {
+        if {$arg eq ""} {
+            if {[llength $argv] == 0} {
+                puts stderr "[file tail $::argv0]: -$opt requires an argument"
+                set opt [expr {[string index $optstring 0] eq ":" ? ":" : "?"}]
+            }
+            set arg [lindex $argv 0]            ;# use next arg, no-op if empty
         }
-        set argv [lreplace $argv 0 0]           ;# consume arg
+        set argv [lreplace $argv 0 0]           ;# consume arg, no-op if empty
+    } else {
+        set arg 1                               ;# boolean flag
     }
 
     return 1