bash-3.2$ [ -n "$(echo 'success' | grep 'failed')" ] && echo 'success' || echo 'failed'
failed
bash-3.2$ alias xxx="[ -n "$(echo 'success' | grep 'failed')" ] && echo 'success' || echo 'failed'"
bash-3.2$ alias xxx
alias xxx='[ -n  ] && echo '\''success'\'' || echo '\''failed'\'''

#!/bin/bash

/etc/init.d/nginx configtest > /dev/null 2>&1
if [ "x0" = "x$?0" ]; then
  /etc/init.d/nginx restart
else
  echo 'error'
fi