gistfile1.txt

test ⚲ ./testopt 
aflag = 0, bflag = 0, cvalue = (null)
test ⚲ ./testopt -a -b
aflag = 1, bflag = 1, cvalue = (null)
test ⚲ ./testopt -c
Option -c requires an argument.
test ⚲ ./testopt -ab
aflag = 1, bflag = 1, cvalue = (null)
test ⚲ ./testopt -c foo
aflag = 0, bflag = 0, cvalue = foo
test ⚲ ./testopt -cfoo
aflag = 0, bflag = 0, cvalue = foo
test ⚲ ./testopt arg1
aflag = 0, bflag = 0, cvalue = (null)
Non-option argument arg1
test ⚲ ./testopt -a arg1
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument arg1
test ⚲ ./testopt -c foo arg1
aflag = 0, bflag = 0, cvalue = foo
Non-option argument arg1
test ⚲ ./testopt -a -- -b
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument -b
test ⚲ ./testopt -a -
aflag = 1, bflag = 0, cvalue = (null)
Non-option argument -