testコマンド 戻り値判定

通常の判定

 [ "a" = "a" ] && echo "OK"

 if [ "a" != "b" ]; then
   echo "OK"
 fi

特殊変数$?による判定

 [ "a" = "a" ]
 if [ $? -eq 0 ]; then
    echo "OK"
 fi

参考

• http://www.ibm.com/developerworks/jp/linux/library/l-bash-test.html
• http://lagendra.s.kanazawa-u.ac.jp/ogurisu/manuals/sh-text/sh/node48.html