split: raise error for -b 0 (#482)

* "perl split -b 0 file" is invalid but did not raise an error due to truth check on $opt{b}
* -b NUMBER has no default value, but it must be >0
* Add explicit checks for options -b, -l and -p which cannot be used together
* test1: "perl split -b 0 file" --> now fails
* test2: "perl split -b 1 file" --> one byte per file
* test3: "perl split -b 5 file" --> final file with <5 bytes (remainder)
* test4: "perl split -l 2 file" --> two lines per file
* test5: "perl split longfile" --> default -l mode: 1000 lines per file

bin/split

@@ -97,6 +97,16 @@ exit 1;
 #### Main program starts here. ####
 
 getopts('b:l:p:', \my %opt) or clue;
+my $nbytes;
+if (defined $opt{'b'}) {
+    $nbytes = get_count($opt{'b'}) or die qq($me: "$opt{b}" is invalid number of bytes\n);
+}
+my $nlines;
+if (defined $opt{'l'}) {
+    $nlines = get_count($opt{'l'}) or die qq($me: "$opt{l}" is invalid number of lines\n);
+}
+clue() if ($nbytes && $nlines);
+clue() if ($opt{'p'} && ($nbytes || $nlines));
 
 my $infile = shift;
 my $prefix = shift;
@@ -118,14 +128,9 @@ else {
 }
 binmode $in;
 ## Byte operations.
-if ($opt{b} and (! $opt{p}) and (! $opt{l})) {
-
+if ($opt{'b'}) {
     my ($chunk, $fh);
-    my $count = get_count ($opt{b});
-
-    unless ($count) { die qq($me: "$opt{b}" is invalid number of bytes.\n) }
-
-    while (read ($in, $chunk, $count) == $count) {
+    while (read ($in, $chunk, $nbytes) == $nbytes) {
 	$fh = nextfile ($prefix);
 	print {$fh} $chunk;
     }
@@ -139,8 +144,7 @@ if ($opt{b} and (! $opt{p}) and (! $opt{l})) {
 }
 
 ## Split on patterns.
-elsif ($opt{p} and (! $opt{b}) and (! $opt{l})) {
-
+elsif ($opt{'p'}) {
     my $regex = $opt{p};
     my $fh = nextfile ($prefix);
 
@@ -151,21 +155,16 @@ elsif ($opt{p} and (! $opt{b}) and (! $opt{l})) {
 }
 
 ## Line operations.
-elsif ((! $opt{p}) and (! $opt{b})) {
-
-    # default is -l 1000  (NOT 1k!)
+elsif ((! $opt{'p'}) and (! $opt{'b'})) {
     my $fh;
-    my $count = (defined $opt{l} ? get_count($opt{l}) : 1000);
+    $nlines = 1000 unless $nlines;
     my $line = 0;
 
-    unless ($count) { die qq($me: "$opt{l}" is invalid number of lines.\n) }
-
     while (<$in>) {
-	$fh = nextfile ($prefix) if $line % $count == 0;
+	$fh = nextfile ($prefix) if $line % $nlines == 0;
 	print {$fh} $_;
 	$line++;
     }
-
 }
 
 else { clue };