nginx startup fail on mac osx 10.9 mavericks

Your ps ... | egrep command is finding itself, not an instance of nginx (look at the "COMMAND" column). Since port 80 is in use, it's likely some other program (maybe the Apache that comes with the OS?) is running and grabbing it. To find out, run:

sudo lsof -i:80

If it's the system Apache ("httpd") program, you can probably shut it down with:

sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist

If that doesn't do it, more info will be needed to figure out what's grabbing port 80 and how it's getting started.

Probably still nginx runnig and listening on port 80. try this command

sudo killall nginx