从cron或rc.local运行时,捕获python子进程的stdout stderr [英] Capture stdout stderr of python subprocess, when it runs from cron or rc.local
问题描述
当我通过 cron或rc.local
做午餐时,访问命令的输出(stderr stdout)时遇到问题,它可以正常工作完美地形成常规外壳,但通过rc.local失败 cat /root/watchdog.py
导入子进程
cmd =('echo TEST | gnokii --config /root/.config/gnokii/config --sendsms + 123456789xx')
#p = subprocess.Popen([cmd,'2>& 1'],stdout = subprocess.PIPE,stderr = subprocess.STDOUT,shell = True)
p = subprocess.Popen([cmd,'2& 1'],stdout = subprocess.PIPE,stderr = subprocess .PIPE,shell = True)
输出= p.stdout.read()
输出+ = p.stderr.read()
logFile = open( / root / logfile,' a +')
#####
#逐行读取的想法:
#output =''
#for iter(p.stdout.readline,' '):
#打印捕获的行:%s%line.rstrip()
##logFile.write(line.rstrip())
#输出+ =行
logFil e.write(输出)
logFile.close()
从控制台运行时的输出看起来像:
/root/watchdog.py
GNOKII版本0.6.30
无法打开日志文件/ root / .cache / gnokii / gnokii-errors
警告:无法打开日志文件,日志将定向到stderr
发送成功,参考号为186!
在我的rc.local中
/root/watchdog.py> /root/mywatchPY.out 2>& 1&
这看起来很有趣:
将子进程stderr重定向到stdout
,但不能解决问题。
任何想法如何在没有完整shell的情况下捕获子进程运行的sdterr / stdout?
您的代码中存在多个问题:
- 当
shell = True
时,将命令及其参数作为字符串传递,否则参数为传递给外壳本身而不是命令 - 您应该使用
stderr = subprocess.STDOUT
而不是2> ;& 1
如果您打算将后者应用于整个管道,而不仅仅是最后一个命令 - 使用
p。 communication()
而不是p.stdout.read()
,p.stderr.read()
,否则,如果任何OS管道缓冲区已满,则子进程可能会停顿 - 如果要重载将输出提取到文件中,则无需先将其另存为字符串
从子进程导入Plex,STPEOUT,STDOUT
中使用open( / root / logfile,'ab' ,0)作为日志文件:
p = Popen(shlex.split('gnokii ... + 123456789xx'),
stdin = PIPE,stdout = logfile,stderr = STDOUT)
p.communicate (b'TEST')
将子进程stderr重定向到stdout 不适用,因为您明确地重定向了 stdout
。
I have problem accessing output (stderr stdout) of a command when I do lunch it via cron or rc.local
It works perfectly form regular shell, but fails via rc.local
cat /root/watchdog.py
import subprocess
cmd = ( 'echo "TEST" |gnokii --config /root/.config/gnokii/config --sendsms +123456789xx ')
#p = subprocess.Popen([cmd, '2>&1'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True)
p = subprocess.Popen([cmd, '2>&1'], stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
output = p.stdout.read()
output += p.stderr.read()
logFile = open("/root/logfile", 'a+')
#####
#Idea to read line by line:
#output = ''
# for line in iter(p.stdout.readline,''):
# print "captured line: %s" % line.rstrip()
# #logFile.write(line.rstrip())
# output += line
logFile.write(output)
logFile.close()
The output when run from console looks like:
/root/watchdog.py
GNOKII Version 0.6.30
Cannot open logfile /root/.cache/gnokii/gnokii-errors
WARNING: cannot open logfile, logs will be directed to stderr
Send succeeded with reference 186!
in my rc.local
/root/watchdog.py > /root/mywatchPY.out 2>&1 &
This looks interesting: Redirect subprocess stderr to stdout but it does not solve the problem.
Any idea howto capture sdterr/stdout of subprocess run without full shell?
There are multiple issues in your code:
- pass the command and its args as a string when
shell=True
otherwise the args are passed to the shell itself instead of the command - you should use
stderr=subprocess.STDOUT
instead of2>&1
if you meant to apply the latter to the whole pipeline and not just the last command in it - use
p.communicate()
instead ofp.stdout.read()
,p.stderr.read()
otherwise the subprocess may stall if any of OS pipe buffers fill up - if you want to redirect the output to a file then you do not need to save it as a string first
import shlex
from subprocess import Popen, PIPE, STDOUT
with open("/root/logfile", 'ab', 0) as logfile:
p = Popen(shlex.split('gnokii ... +123456789xx'),
stdin=PIPE, stdout=logfile, stderr=STDOUT)
p.communicate(b'TEST')
Redirect subprocess stderr to stdout doesn't apply because you redirect stdout
explicitly.
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