Linux中Python子进程之间管道的困难

Posted 2023-02-23

【中文标题】Linux中Python子进程之间管道的困难

【英文标题】：Difficulties in pipes between Python subprocesses in Linux

【发布时间】：2021-03-30 17:35:51

【问题描述】：

以下脚本（应该从 p1 获取输出并将其通过管道传输到 p2，然后在终端中输出结果）似乎无法按预期工作。

代码如下：

#!/binr/bin/python
# Script to lauch mosquitto_sub to monitor a mqtt topic -- SYNTAX : mosk topic
import sys
import subprocess

total = len(sys.argv)
cmdargs = str(sys.argv)
print ("The total numbers of args passed to the script: %d " % total)
print ("Args list: %s " % cmdargs)
# Pharsing args one by one 
print ("Script name: %s" % str(sys.argv[0]))
print ("First argument: %s" % str(sys.argv[1]))


path = str(sys.argv[1])
print (path)


p1 = subprocess.Popen(['mosquitto_sub','-h','192.168.1.100','-t',path,'-v'], shell=False, stdout=subprocess.PIPE)
p2 = subprocess.Popen(['ts'], stdin=p1.stdout, shell=False, stdout=subprocess.PIPE)

for line in p2.stdout:
    sys.stdout.write(line)

输入如下“./mosk2.py test/+”，并在通过 mosquitto 发布相关主题的 MQTT 时，我从未在终端中获得预期的输出

【参考方案1】：

已解决 - 我最终巧妙地解决了问题（作弊），如下所示：

cmd = "mosquitto_sub -h 192.168.1.100 -v -t " + topic + " | ts"
print "The command which was executed is : " , cmd

def run_command(command):
    process = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True)
    while True:
        output = process.stdout.readline()
        if output == '' and process.poll() is not None:
            break
        if output:
            print output.strip()
    rc = process.poll()
    return rc

run_command(cmd) #This is the lauch of the actual command