Grep output of command and use it in “if” statement, bash

问题

Okay so here's another one about the StarMade server.

Previously I had this script for detecting a crash, it would simply search through the logs:

#!/bin/bash
cd "$(dirname "$0")"
if ( grep "[SERVER] SERVER SHUTDOWN" log.txt.0); then
sleep 7; kill -9 $(ps -aef | grep -v grep | grep 'StarMade.jar' | awk '{print $2}')
fi

It would find "[SERVER] SERVER SHUTDOWN" and kill the process after that, however this is not a waterproof method, because with different errors it could be possible that the message doesn't appear, rendering this script useless.

So I have this tool that can send commands to the server, but returns an EOF exception when the server is in a crashed state. I basically want to grab the output of this command, and use it in the if-statement above, instead of the current grep command, in such a way that it would execute the commands below when the grep finds "java.io.EOFException".

I could make it write the output to a file and then grep it from there, but I wonder, isn't there a better/more efficient method to do this?

EDIT: okay, so after a bit of searching I put together the following:

if ( java -jar /home/starmade/StarMade/StarNet.jar xxxxx xxxxx /chat) 2>&1 > /dev/null |grep java.io.EOFException);

Would this be a valid if-statement? I need it to match "java.io.EOFException" in the output of the first command, and if it matches, to execute something with "then" (got that part working).

回答1:

Not sure to solve your problem, but this line:

ps -aef | grep -v grep | grep 'StarMade.jar' | awk '{print $2}'

could be change to

ps -aef | awk '/[S]tarMade.jar/ {print $2}'

The [S] prevents awk from finding itself.

Or just like this to get the pid

pidof StarMade.jar

来源：https://stackoverflow.com/questions/19838118/grep-output-of-command-and-use-it-in-if-statement-bash

标签

bash

if-statement

grep

command

output