# Open Group Base Specifications Issue 7:
# """
# If an unknown option is met, VAR shall be set to "?". In this case,
# if the first character in optstring is ":", OPTARG shall be set
# to the option character found, but no output shall be written
# to standard error; otherwise, the shell variable OPTARG shall be
# unset and a diagnostic message shall be written to standard error."
# ...
# If an option-argument is missing:
# If the first character of optstring is ":", VAR shall be set to ":"
# and OPTARG shall be set to the option character found.
# """

echo "*** optstring:':ac' args:-a -b -c"
getopts ":ac" var -a -b -c; echo "1 rc:$? var:'$var' OPTIND:$OPTIND OPTARG:'$OPTARG'"
getopts ":ac" var -a -b -c; echo "2 rc:$? var:'$var' OPTIND:$OPTIND OPTARG:'$OPTARG'"
getopts ":ac" var -a -b -c; echo "3 rc:$? var:'$var' OPTIND:$OPTIND OPTARG:'$OPTARG'"
getopts ":ac" var -a -b -c; echo "4 rc:$? var:'$var' OPTIND:$OPTIND OPTARG:'$OPTARG'"
# Previous line should result in "rc:1", which is normally treated
# in getopts loops as exit condition.
# Nevertheless, let's verify that calling it yet another time doesn't do
# anything weird:
getopts ":ac" var -a -b -c; echo "5 rc:$? var:'$var' OPTIND:$OPTIND OPTARG:'$OPTARG'"