seq(1)

bin/seq

@@ -1,44 +1,52 @@
 #!/bin/sh
 
+# There are many bugs and limitations with this implementation as opposed to
+# others, particularly NetBSD's. This should probably be rewritten in C.
+
 argv0="$0"
 
-nai() {
-	printf "$argv0: $1: Not an integer\n"
+doublecheck() {
+	! str isdigit "$1" \
+		&& printf "%s: %s: Not an unsigned integer.\n" \
+			"$argv0" "$1" 1>&2 \
+		&& exit 1 \
+		|| return 0
+}
+
+error() {
+	printf "%s: Internal error.\n"
+		"$argv0" 1>&2
 	exit 1
 }
 
 usage() {
-	printf "Usage:\n \
-	$argv0 [last]
-	$argv0 [first] [last]
-	$argv0 [first] [increment] [last]\n" \
-		>/dev/stderr
+	printf "\
+Usage:
+	%s [last]
+	%s [first] [last]
+	%s [first] [increment] [last]
+" "$argv0" "$argv0" "$argv0" 1>&2
 	exit 1
 }
 
-[ -n "$1" ] || usage
-if [ -n "$3" ]; then
-	stris int "$3" \
-		|| nai "$3" \
-		&& last=$3
-	stris int "$2" \
-		|| nai "$2" \
-		&& increment=$2
-	stris int "$1" \
-		|| nai "$1" \
-		&& first=$1
-elif [ -n "$2" ]; then
-	stris int "$2" \
-		|| nai "$2" \
-		&& last=$2
-	stris int "$1" \
-		|| nai "$1" \
-		&& first=$1
-	increment=1
-else
-	stris int "$1" \
-		|| nai "$1" \
-		&& last=$1
-	first=1
-	increment=1
+test -n "$1" && test -z "$4" || usage
+
+test -n "$3" && doublecheck "$3"
+test -n "$2" && doublecheck "$2"
+test -n "$1" && doublecheck "$1"
+
+# all args are guaranteed to be positive integers; no need to quote variables
+
+if   test -n "$3"; then first=$1; increment=$2; last=$3
+elif test -n "$2"; then first=$1; increment=1;  last=$2
+else                    first=1;  increment=1;  last=$1
 fi
+
+i=$first
+while true; do
+	printf "%s\n" $i
+	i=$(printf "%s %s + p\n" $i $increment | dc)
+	printf "%s %s - p\n" $last $i | dc | grep '\-' >/dev/null 2>&1 \
+		&& break \
+		|| continue
+done