known_hostsに保存されているホストキーを更新する。詳細はこちら→http://qiita.com/kawaz/items/20983ec286088a1ae5c7

refresh_knownhosts.sh

#!/bin/bash

# ssh設定値の取得関数
sshconf() {
  local key=$1 targethost=$2
  local value inhost f k v m
  [[ -z $key ]] && { echo "Usage: $FUNCNAME key [hostname]"; return 1; }
  for f in ~/.ssh/config /etc/ssh_config; do
    [[ -r $f ]] || continue
    inhost=1
    while read k v; do
      if [[ $k == Host ]]; then
        inhost=
        for m in $v; do
          [[ $m =~ ^# ]] && break # skip comment
          m=${m//./\\.}; m=${m//\*/.*}; m=${m//\?/.}; m="^$m$" # wildcard -> regexp
          if [[ $targethost =~ $m ]]; then
            inhost=1
            break
          fi
        done
        continue
      fi
      [[ -z $inhost ]] && continue # 不一致Host内の設定は無視
      if [[ $k == $key ]]; then
        value=$v
      fi
      if [[ -n $value ]]; then
        break # 最初に見つけた設定優先なのでbreak
      fi
    done < <(cat $f | grep -v '^$' | egrep -v '^\s*#')
    if [[ -n $value ]]; then
      break # 最初のファイル優先なのでbreak
    fi
  done
  [[ -z $value ]] && return 1
  printf "%s\n" "$value"
}

# main
[[ -z $1 ]] && { echo "Usage: $0 hostname [hostname...]"; exit 1; }
hashopt=
if [[ $(sshconf HashKnownHosts) == yes ]]; then
  hashopt=-H
fi
for h in "$@"; do
  ssh-keygen -R "$h"
  ssh-keyscan $hashopt "$h" >> ~/.ssh/known_hosts
done

sshconf.sh

# ssh設定値の取得関数
sshconf() {
  local key=$1 targethost=$2
  local value inhost f k v m
  [[ -z $key ]] && { echo "Usage: $0 key [hostname]"; return 1; }
  for f in ~/.ssh/config /etc/ssh_config; do
    [[ -r $f ]] || continue
    inhost=1
    while read k v; do
      if [[ $k == Host ]]; then
        inhost=
        for m in $v; do
          [[ $m =~ ^# ]] && break # skip comment
          m=${m//./\\.}; m=${m//\*/.*}; m=${m//\?/.}; m="^$m$" # wildcard -> regexp
          if [[ $targethost =~ $m ]]; then
            inhost=1
            break
          fi
        done
        continue
      fi
      [[ -z $inhost ]] && continue # 不一致Host内の設定は無視
      if [[ $k == $key ]]; then
        value=$v
      fi
      if [[ -n $value ]]; then
        break # 最初に見つけた設定優先なのでbreak
      fi
    done < <(cat $f | grep -v '^$' | egrep -v '^\s*#')
    if [[ -n $value ]]; then
      break # 最初のファイル優先なのでbreak
    fi
  done
  [[ -z $value ]] && return 1
  printf "%s\n" "$value"
}

sshの設定取得関数単体でも便利そうなので、sshconf.sh として独立したファイルに分離してみた。