docs: rewrite README usage and examples

README.md

@@ -1,111 +1,42 @@
-#!/bin/bash
+# sshrm
 
-set -euo pipefail
+Remove an entry from `~/.ssh/known_hosts` by host name or by line number.
 
-readonly FILENAME="${HOME}/.ssh/known_hosts"
-readonly BACKUP_FILE="${FILENAME}.sshrm.bak"
+## Usage
 
-check_known_hosts() {
-	if [ ! -f "${FILENAME}" ]; then
-		error "known_hosts not found."
-		exit 1
-	fi
-}
+```bash
+sshrm [-h|--help] [--no-backup] host|line_number
+```
 
-usage() {
-	echo "Usage: sshrm [-h|--help] [--no-backup] host|line_number"
-}
+## Options
 
-confirm() {
-	read -r -p "Proceed? [y/N] " answer
-	case "$answer" in
-		y|Y|yes|YES)
-			return 0
-			;;
-		*)
-			error "cancelled."
-			return 1
-			;;
-	esac
-}
+- `-h`, `--help` Show help and exit.
+- `--no-backup` Skip creating `~/.ssh/known_hosts.sshrm.bak`.
 
-error() {
-	echo "Error: $1"
-}
+## Examples
 
-is_number() {
-	case "$1" in
-		''|*[!0-9]*) return 1 ;;
-		*) return 0 ;;
-	esac
-}
+Remove by host:
 
-get_host_from_line() {
-	awk -v line="$1" 'NR == line {print $1; exit}' "${FILENAME}"
-}
+```bash
+sshrm example.com
+```
 
-create_backup() {
-	cp "${FILENAME}" "${BACKUP_FILE}"
-}
+Remove by line number:
 
-remove_host() {
-	ssh-keygen -R "$1"
-}
+```bash
+sshrm 12
+```
 
-if [ "${1-}" = "" ]; then
-	error "missing argument."
-	usage
-	exit 1
-fi
+Remove without backup:
 
-if [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
-	usage
-	exit 0
-fi
+```bash
+sshrm --no-backup example.com
+```
 
-backup=true
-if [ "$1" = "--no-backup" ]; then
-	backup=false
-	shift
-fi
+## Notes
 
-if [ "${1-}" = "" ]; then
-	error "missing argument."
-	usage
-	exit 1
-fi
-
-if [ "${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."
-		exit 1
-	fi
-else
-	HOST="$1"
-fi
-
-if ! confirm; then
-	exit 1
-fi
-
-if [ "${backup}" = true ]; then
-	create_backup
-fi
-
-if ! remove_host "$HOST"; then
-	error "removal failed."
-	exit 1
-fi
+- 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.