docs: rewrite README usage and examples

.continue/rules/project.md

@@ -11,7 +11,7 @@ description: SSHRM project conventions
 - Prefer minimal, focused changes that do not alter the intent of the existing scripts, unless the script behavior is intentionally updated.
 - Maintain `.continue/rules/project.md` whenever project conventions or script behavior change.
 - `sshrm` is implemented as a small Bash script with helper functions, while preserving host and line-number removal behavior.
-- `sshrm` should print a short usage line, support `-h`/`--help`, fail clearly on missing or invalid line-number input, and may support a dedicated `--no-backup` option with a `known_hosts.sshrm.bak` backup file.
+- `sshrm` should print a short usage line, support `-h`/`--help`, fail clearly on missing or invalid line-number input, reject extra arguments, may support a dedicated `--no-backup` option with a `known_hosts.sshrm.bak` backup file, and now asks for confirmation before removal.
 
 # Project identity
 - Main script: `sshrm`

README.md

@@ -5,12 +5,13 @@ Remove an entry from `~/.ssh/known_hosts` by host name or by line number.
 ## Usage
 
 ```bash
-sshrm [OPTION]... HOST|LINE
+sshrm [-h|--help] [--no-backup] host|line_number
 ```
 
 ## Options
 
 - `-h`, `--help` Show help and exit.
+- `--no-backup` Skip creating `~/.ssh/known_hosts.sshrm.bak`.
 
 ## Examples
 
@@ -26,9 +27,16 @@ Remove by line number:
 sshrm 12
 ```
 
+Remove without backup:
+
+```bash
+sshrm --no-backup example.com
+```
+
 ## Notes
 
 - Line numbers must be positive integers.
+- Extra arguments are rejected.
+- The script asks for confirmation before removal.
 - The script edits `~/.ssh/known_hosts`.
 - Keep a backup if you need to recover entries.
-

sshrm

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-set -u
+set -euo pipefail
 
 readonly FILENAME="${HOME}/.ssh/known_hosts"
 readonly BACKUP_FILE="${FILENAME}.sshrm.bak"
@@ -39,6 +39,20 @@ remove_host() {
 	ssh-keygen -R "$1"
 }
 
+confirm() {
+	local prompt="$1"
+	read -r -p "Remove ${prompt}? [y/N] " answer
+	case "$answer" in
+		y|Y|yes|YES)
+			return 0
+			;;
+		*)
+			error "cancelled."
+			return 1
+			;;
+	esac
+}
+
 if [ "${1-}" = "" ]; then
 	error "missing argument."
 	usage
@@ -62,9 +76,19 @@ if [ "${1-}" = "" ]; then
 	exit 1
 fi
 
+if [ "${2-}" != "" ]; then
+	error "too many arguments."
+	usage
+	exit 1
+fi
+
 check_known_hosts
 
 if is_number "$1"; then
+	if [ "$1" -eq 0 ]; then
+		error "invalid line number."
+		exit 1
+	fi
 	HOST="$(get_host_from_line "$1")"
 	if [ "${HOST}" = "" ]; then
 		error "invalid line number."
@@ -74,8 +98,15 @@ else
 	HOST="$1"
 fi
 
+if ! confirm "$HOST"; then
+	exit 1
+fi
+
 if [ "${backup}" = true ]; then
 	create_backup
 fi
 
-remove_host "$HOST"
+if ! remove_host "$HOST"; then
+	error "removal failed."
+	exit 1
+fi