从python第二行读取文本文件内容

Question

I wrote a python code which executes the bash command and save the output in txt file, now i want to read the txt file which actually contains details from line 2 always, and print true if output exists and send a mail to the user.

Looking for a further solution how I can read specific second line output of file output.txt and print true if the line exists to send a mail to the user otherwise goodbye.

Am very new to this approach, please help with your guidance. TIA.

import subprocess
p = subprocess.Popen("bash command > output.txt", stdout=subprocess.PIPE, shell=True)
(output, err) = p.communicate()
p_status = p.wait()
print "command exit status/return code: ", p_status

Above code prints the output in the txt file in the below format

PID  PPID %CPU     ELAPSED COMMAND
3435 1     0       4-05:20:09 

Requirement: Read from "3435 1 0 4-05:20:09 " this line and print true as line exist and send a mail to user. If not output after "PID PPID %CPU ELAPSED COMMAND" it should send no mail

Answer 1

you can use it like this:

lines = output.split('\n')

Now you can access lines by index eg lines[1] or lines[1:] .

You need to remove > output.txt from your command to get the output in output variable instead of output.txt file

Answer 2

You can create list of lines from a file like this:

with open('output.txt') as input_file:
    lines_list = input_file.readlines()    
if len(lines_list) > 1:
    lines_list=lines_list[1:] # drop the first line
    send_mail()
else:
    print ("else condition")

you open a file for reading using "r" and you build a list of lines. if the list is longer then 1, you build a new list by dropping the first line