How to get only one specific line from subprocess output

» python » How to get only one specific line from subprocess output

By : user2957064

Date : November 23 2020, 01:01 AM

wish helps you I know how to search if specific word exists in subprocess output. But how can I print out only one specific line, if I know this line always looks like:

code :

import subprocess
p = subprocess.Popen(["some", "command"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
stdout, stderr = p.communicate()
stdout=stdout.split("\n")
for line in stdout:
    if line.startswith("This is the line:"):
        print line

Share :

Real time output of subprocess.popen() and not line by line

By : Mish Leemp

Date : March 29 2020, 07:55 AM

help you fix your problem Could be two things...
It's likely that readline is changing some things from the output of your program. I believe \r is carriage return and tells the terminal to return to the beginning of the line and then the program can output overtop the text it just output. Readline is most likely removing this.

code :

p = subprocess.Popen(args, stdout=subprocess.PIPE, \
                     stderr=subprocess.PIPE, \
                     universal_newlines=True)
for line in iter(p.stdout.readline, ""):
    sys.stdout.write('\r'+line[:-1])
    sys.stdout.flush()

Check if subprocess is still running while reading its output line by line

By : InJoo Kim

Date : March 29 2020, 07:55 AM

should help you out I am starting a subprocess in Python and trying to read each line of output. Unfortunately I can't find a good way of testing if my processes is still alive. The standard method seems to be checking poll(), but that seems to always return None. Here is my code. , to process subprocess output line by line, try this:

code :

p = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=1)
while p.poll() is None:
    line = p.stdout.readline()
    ...do something with the line here

Printing specific line from subprocess.Popen output

By : TV HOURS

Date : March 29 2020, 07:55 AM

I wish did fix the issue. These are bytes instead of strings, see for example https://docs.python.org/3/reference/lexical_analysis.html#literals

code :

line = proc.stdout.readline().decode()

subprocess run in background and write output line by line to a file

By : user2393530

Date : March 29 2020, 07:55 AM

will be helpful for those in need Both the buffers of the filehandler as the subprocess can be set to 'line-buffering', where a newline character causes each object's buffer to be forwarded. This is done by setting the buffer parameter to 1, see open() command and subprocess.
You need to make sure that the child process will not buffer by itself. By seeing that you are running a Python script too, you either need to implement this in the code there, like flush=True for a print statement:

code :

print(this_and_that, flush=True)

How do I wait for a subprocess to finish, store it's output and add a prefix (without a new line) to the output?

By : user2537746

Date : March 29 2020, 07:55 AM

help you fix your problem First you need to import the sys module, so you can use sys.stdout's write and flush methods.

code :

import sys

import subprocess

sys.stdout.write("Prefix: ")

response = subprocess.check_output(["cmd", "--option", "filename.x"])

sys.stdout.write(response.decode("UTF-8"))

sys.stdout.flush()

import sys, subprocess
sys.stdout.write("Prefix: ")
response = subprocess.check_output(["cmd", "--option", "filename.x"])
sys.stdout.write(response.decode("UTF-8"))
sys.stdout.flush()