用kill命令发送一个信号0去检测，别用ps -ef pid|grep，会有误判的存在！
先决条件.进程id要写入pid文件，python做法
def write_pidfile(pidfile):
if os.path.isfile(pidfile):
with open(pidfile, ‘r‘) as f:
old_pid = f.readline()
if old_pid:
old_pid = int(old_pid)
try: os.kill(old_pid, 0)
except: pass
else: return False
with open(pidfile, ‘w+‘) as f:
f.write("%d" % os.getpid())
return True
if os.path.isfile(pidfile):
with open(pidfile, ‘r‘) as f:
old_pid = f.readline()
if old_pid:
old_pid = int(old_pid)
try: os.kill(old_pid, 0)
except: pass
else: return False
with open(pidfile, ‘w+‘) as f:
f.write("%d" % os.getpid())
return True
然后使用$?表示上一个命令的执行结果是否正常退出（非0）则表示进程信号0已经发布过去，进程不存在。
#!/bin/bash
PID_FILE="/home/machen/search_correct/data/search_correct.pid"
if [ -e $PID_FILE ];
then
PID=`cat $PID_FILE`
kill -0 $PID; #check if process id exists
if [ ! $? -eq 0 ]; #don‘t exists, boot one
then
/usr/local/bin/python2.7 /home/machen/search_correct/main.py -l
else
echo "process pid: $PID still exists. wait ..."
fi
fi
PID_FILE="/home/machen/search_correct/data/search_correct.pid"
if [ -e $PID_FILE ];
then
PID=`cat $PID_FILE`
kill -0 $PID; #check if process id exists
if [ ! $? -eq 0 ]; #don‘t exists, boot one
then
/usr/local/bin/python2.7 /home/machen/search_correct/main.py -l
else
echo "process pid: $PID still exists. wait ..."
fi
fi
帖子帮助了我
kill is somewhat misnamed in that it doesn‘t necessarily kill the process. It just sends the process a signal. kill $PID is equivalent to kill -15 $PID, which sends signal 15, SIGTERM to the process, which is an instruction to terminate. There isn‘t a signal 0, that‘s a special value telling kill to just check if a signal could be sent to the process, which is for most purposes more or less equivalent to checking if it exists. See linux.die.net/man/2/kill and linux.die.net/man/7/signal – Christoffer HammarstrmJun 15 ‘10 at 10:58
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