bin/lines: Add working version

1 files changed, 81 insertions, 0 deletions

diff --git a/bin/lines b/bin/lines
new file mode 100755
index 0000000..b2558b8
--- /dev/null
+++ b/bin/lines
@@ -0,0 +1,81 @@
+#!/bin/sh
+set -eu
+
+usage() {
+	cat <<-'EOF'
+		Usage:
+		  lines START [END]
+		  lines -h
+	EOF
+}
+
+help() {
+	cat <<-'EOF'
+
+		Options:
+		  -h, --help    show this message
+
+		  START         the nth line number to start showing
+		  END           the nth line number to stop
+		                showing (default: START + 1)
+
+
+		Print the range START-END of lines of the content of STDIN.
+
+
+		Examples:
+
+		  Print 3rd line:
+
+		    $ seq 10 | lines 3
+		    3
+
+
+		  Print lines 5~8:
+
+		    $ lines 5 8 < file.txt
+	EOF
+}
+
+
+for flag in "$@"; do
+	case "$flag" in
+		--)
+			break
+			;;
+		--help)
+			usage
+			help
+			exit
+			;;
+		*)
+			;;
+	esac
+done
+
+while getopts 'h' flag; do
+	case "$flag" in
+		h)
+			usage
+			help
+			exit
+			;;
+		*)
+			usage >&2
+			exit 2
+			;;
+	esac
+done
+shift $((OPTIND - 1))
+
+START="${1:-}"
+
+if [ -z "${2:-}" ]; then
+	END=1
+else
+	END=$(($2 - $START + 1))
+fi
+
+eval "$(assert-arg "$START" 'START')"
+
+tail -n +"$START" | head -n "$END"