Bash脚本命令未运行

Question

I have seafile ( http://www.seafile.com/en/home/ ) running on my NAS and I set up a cron tab that runs a script every few minutes to check if the seafile server is up, and if not, it will start it

The script looks like this:

#!/bin/bash
# exit if process is running
if ps aux | grep "[s]eafile" > /dev/null
then exit
else
# restart process
/home/simon/seafile/seafile-server-latest/seafile.sh start
/home/simon/seafile/seafile-server-latest/seahub.sh start-fastcgi
fi

running /home/simon/seafile/seafile-server-latest/seafile.sh start and /home/simon/seafile/seafile-server-latest/seahub.sh start-fastcgi individually/manually works without a problem, but when I try to manually run this script file, neither of those lines execute and seafile/seahub do not start

Is there an error in my script that is preventing execution of those 2 lines? I've made sure to chmod the script file to 755

Answer 1

The problem is likely that when you pipe commands into one another, you don't guarentee that the second command doesn't start before the first (it can start, but not do anything while it waits for input). For example:

oj@ironhide:~$ ps -ef | grep foo
oj        8227  8207  0 13:54 pts/1    00:00:00 grep foo

There is no process containing the word "foo" running on my machine, but the grep that I'm piping ps to appears in the process list that ps produces.

You could try using pgrep instead, which is pretty much designed for this sort of thing:

if pgrep "[s]eafile"

Or you could add another pipe to filter out results that include grep :

ps aux | grep "[s]eafile" | grep -v grep

Answer 2

If the name of this script matches the regex [s]eafile it will trivially always take the exit branch.

You should probably be using pidof in preference of reinventing the yak shed anyway.

Answer 3

turns out the script itself was working ok, although the change to using pgrep is much nicer. the problem was actually in the crontab (didn't include the sh in the command)