Related
I have a cmd file "file.cmd" containing 100s of lines of command.
Example
pandoc --extract-media -f docx -t gfm "sample1.docx" -o "sample1.md"
pandoc --extract-media -f docx -t gfm "sample2.docx" -o "sample2.md"
pandoc --extract-media -f docx -t gfm "sample3.docx" -o "sample3.md"
I am trying to run these commands using a script so that I don't have to go to a file and click on it.
This is my code, and it results in no output:
file1 = open('example.cmd', 'r')
Lines = file1.readlines()
# print(Lines)
for i in Lines:
print(i)
os.system(i)
You don't need to read the cmd file line by line. you can simply try the following:
import os
os.system('myfile.cmd')
or using the subprocess module:
import subprocess
p = subprocess.Popen(['myfile.cmd'], shell = True, close_fds = True)
stdout, stderr = proc.communicate()
Example:
myfile.cmd:
#ECHO OFF
ECHO Grettings From Python!
PAUSE
script.py:
import os
os.system('myfile.cmd')
The cmd will open with:
Greetings From Python!
Press any key to continue ...
You can debug the issue by knowing the return exit code by:
import os
return_code=os.system('myfile.cmd')
assert return_code == 0 #asserts that the return code is 0 indicating success!
Note: os.system works by calling system() in C can only take up to 65533 arguments after a command (so it is a 16 bit issue). Giving one more argument will result in the return code 32512 (which implies the exit code 127).
The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function (os.system('command')).
since it is a command file (cmd), and only the shell can run it, then shell argument must set to be true. since you are setting the shell argument to true, the command needs to be string form and not a list.
use the Popen method for spawn a new process and the communicte for waiting on that process (you can time it out as well). if you whish to communicate with the child process, provide the PIPES (see mu example, but you dont have to!)
the code below for python 3.3 and beyond
import subprocess
try:
proc=subprocess.Popen('myfile.cmd', shell=True, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
outs, errs = proc.communicate(timeout=15) #timing out the execution, just if you want, you dont have to!
except TimeoutExpired:
proc.kill()
outs, errs = proc.communicate()
for older python versions
proc = subprocess.Popen('myfile.cmd', shell=True)
t=10
while proc.poll() is None and t >= 0:
print('Still waiting')
time.sleep(1)
t -= 1
proc.kill()
In both cases (python versions) if you dont need the timeout feature and you dont need to interact with the child process, then just, use:
proc = subprocess.Popen('myfile.cmd', shell=True)
proc.communicate()
This is a direct clarification question to the answer in here which I thought it worked, but it does not!
I have the following test bash script (testbash.sh) which just creates some output and a lot of errors for testing purposes (running on Red Hat Enterprise Linux Server release 7.6 (Maipo) and also Ubuntu 16.04.6 LTS):
export MAX_SEED=2
echo "Start test"
pids=""
for seed in `seq 1 ${MAX_SEED}`
do
python -c "raise ValueError('test')" &
pids="${pids} $!"
done
echo "pids: ${pids}"
wait $pids
echo "End test"
If I run this script I get the following output:
Start test
pids: 68322 68323
Traceback (most recent call last):
File "<string>", line 1, in <module>
ValueError: test
Traceback (most recent call last):
File "<string>", line 1, in <module>
ValueError: test
[1]- Exit 1 python -c "raise ValueError('test')"
[2]+ Exit 1 python -c "raise ValueError('test')"
End test
That is the expected outcome. That is fine. I want to get errors!
Now here is the python code that is supposed to catch all the output:
from __future__ import print_function
import sys
import time
from subprocess import PIPE, Popen, STDOUT
from threading import Thread
try:
from queue import Queue, Empty
except ImportError:
from Queue import Queue, Empty # python 2.x
ON_POSIX = 'posix' in sys.builtin_module_names
def enqueue_output(out, queue):
for line in iter(out.readline, b''):
queue.put(line.decode('ascii'))
out.close()
p = Popen(['. testbash.sh'], stdout=PIPE, stderr=STDOUT, bufsize=1, close_fds=ON_POSIX, shell=True)
q = Queue()
t = Thread(target=enqueue_output, args=(p.stdout, q))
t.daemon = True # thread dies with the program
t.start()
# read line without blocking
while t.is_alive():
#time.sleep(1)
try:
line = q.get(timeout=.1)
except Empty:
print(line)
pass
else:
# got line
print(line, end='')
p.wait()
print('returncode = {}'.format(p.returncode))
But when I run this code I only get the following output:
Start test
pids: 70191 70192
Traceback (most recent call last):
returncode = 0
or this output (without the line End test):
Start test
pids: 10180 10181
Traceback (most recent call last):
File "<string>", line 1, in <module>
ValueError: test
Traceback (most recent call last):
File "<string>", line 1, in <module>
ValueError: test
returncode = 0
Most of the above output is missing! How can I fix this? Also, I need some way to check if any command in the bash script did not succeed. In the example this is the case, but the errorcode printed out is still 0. I expect an errorcode != 0.
It is not important to immediately get the output. A delay of some seconds is fine. Also if the output order is a bit mixed up this is of no concern. The important thing is to get all the output (stdout and stderr).
Maybe there is a simpler way to just get the output of a bash script which is started from python?
To be run with python3
from __future__ import print_function
import os
import stat
import sys
import time
from subprocess import PIPE, Popen, STDOUT
from threading import Thread
try:
from queue import Queue, Empty
except ImportError:
from Queue import Queue, Empty # python 2.x
ON_POSIX = 'posix' in sys.builtin_module_names
TESTBASH = '/tmp/testbash.sh'
def create_bashtest():
with open(TESTBASH, 'wt') as file_desc:
file_desc.write("""#!/usr/bin/env bash
export MAX_SEED=2
echo "Start test"
pids=""
for seed in `seq 1 ${MAX_SEED}`
do
python -c "raise ValueError('test')" &
pids="${pids} $!"
sleep .1 # Wait so that error messages don't get out of order.
done
wait $pids; return_code=$?
sleep 0.2 # Wait for background messages to be processed.
echo "pids: ${pids}"
echo "End test"
sleep 1 # Wait for main process to handle all the output
exit $return_code
""")
os.chmod(TESTBASH, stat.S_IEXEC|stat.S_IRUSR|stat.S_IWUSR)
def enqueue_output(queue):
pipe = Popen([TESTBASH], stdout=PIPE, stderr=STDOUT,
bufsize=1, close_fds=ON_POSIX, shell=True)
out = pipe.stdout
while pipe.poll() is None:
line = out.readline()
if line:
queue.put(line.decode('ascii'))
time.sleep(.1)
print('returncode = {}'.format(pipe.returncode))
create_bashtest()
C_CHANNEL = Queue()
THREAD = Thread(target=enqueue_output, args=(C_CHANNEL,))
THREAD.daemon = True
THREAD.start()
while THREAD.is_alive():
time.sleep(0.1)
try:
line = C_CHANNEL.get_nowait()
except Empty:
pass # print("no output")
else:
print(line, end='')
Hope this helps :
First, looks like buffers are not being flushed. Redirecting (and, to be safe, appending) stdout/stderr to a file(s) rather than to the terminal, may help. You can always use tee (or tee -a) if you really want both. Using context managers 'might' help.
As far as the zero return code, $!
https://unix.stackexchange.com/questions/386196/doesnt-work-on-command-line
! may be invoking history invoking history, thereby $! resulting in an empty value.
If you somehow end up with just a bare wait the return code will be a zero. Regardless, return codes can be tricky, and you might be picking a successful return code from elsewhere.
Take a look at stdbuf command to change the buffer sizes for stdout and stderr:
Is there a way to flush stdout of a running process
That may also help with getting the rest of your expected output.
Rewrite the while block this way:
# read line without blocking
while t.is_alive():
try:
line = q.get(block=False)
except Empty:
# print(line)
pass
else:
# got line
print(line, end='')
You don't want to block on getting a line from the Queue when there's none, and you don't need a timeout in this case, as it's only used when blocking the thread is required. Consequently, if the Queue.get() throws Empty, there's no line to print, and we just pass.
===
Also, let's clarify the script execution logic.
Since you're using Bash expressions, and the default shell used by Popen is /bin/sh, you'd probably want to rewrite the invokation line this way:
p = Popen(['/usr/bin/bash','-c', './testbash.sh'], stdout=PIPE, stderr=STDOUT, bufsize=1, close_fds=ON_POSIX)
It won't hurt to add a shebang to your shell script, too:
#!/usr/bin/env bash
<... rest of the script ...>
If you're looking for these lines:
[1]- Exit 1 python -c "raise ValueError('test')"
[2]+ Exit 1 python -c "raise ValueError('test')"
This is a function of the bash shell that's typically only available in interactive mode, i.e. when you're typing commands into a terminal. If you check the bash source code, you can see that it explicitly checks the mode before printing to stdout/stderr.
In the more recent versions of bash, you can't set this inside a script: see https://unix.stackexchange.com/a/364618 . However, you can set this yourself when starting the script:
p = Popen(['/bin/bash -i ./testbash.sh'], stdout=PIPE, stderr=STDOUT, bufsize=1, close_fds=ON_POSIX, shell=True)
I will note that this is only working for me on Python3 - Python2 is only getting part of the output. It isn't clear version of Python you're using, but considering Python2 is end of life now we should probably all be trying to switch to Python3.
As for the bash script, even with interactive mode set it seems you have to change how you wait to get that output:
#!/bin/bash
export MAX_SEED=2
echo "Start test"
pids=""
for seed in `seq 1 ${MAX_SEED}`
do
python -c "raise ValueError('test')" &
pids="${pids} $!"
done
echo "pids: ${pids}"
wait -n $pids
wait -n $pids
ret=$?
echo "End test"
exit $ret
Normal wait wasn't working for me (Ubuntu 18.04), but wait -n seemed to work - but as it only waits for the next job to complete, I had inconsistent output just calling it once. Calling wait -n for each job launched seems to do the trick, but the program flow should probably be refactored to loop over the wait the same number of times you spin up the job.
Also note that to change the return code of the script, Philippe's answer has the right approach - the $? variable has the return code of the latest command that failed, which you can then pass to exit. (Yet another difference in Python versions: Python2 is returning 127 while Python3 returns 1 for me.) If you need the return values for each job, one way might be to parse out the values in the interactive job exit lines.
Just guessing - could it be that a line that starts with an empty character / space is not recognized as a line by your logic.
Maybe this indent is the issue. Another option is, that there is a tab or something like that and the ascii decode might fail.
This is how I usually use subprocess:
import subprocess
with subprocess.Popen(["./test.sh"], shell=True, stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE) as p:
error = p.stderr.read().decode()
std_out = p.stdout.read().decode()
if std_out:
print(std_out)
if error:
print("Error message: {}".format(error))
Here you decode and read both the stdout and the stderr. You get everything but not in the same order, I don't if that's an issue.
I want to write a function that will execute a shell command and return its output as a string, no matter, is it an error or success message. I just want to get the same result that I would have gotten with the command line.
What would be a code example that would do such a thing?
For example:
def run_command(cmd):
# ??????
print run_command('mysqladmin create test -uroot -pmysqladmin12')
# Should output something like:
# mysqladmin: CREATE DATABASE failed; error: 'Can't create database 'test'; database exists'
In all officially maintained versions of Python, the simplest approach is to use the subprocess.check_output function:
>>> subprocess.check_output(['ls', '-l'])
b'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
check_output runs a single program that takes only arguments as input.1 It returns the result exactly as printed to stdout. If you need to write input to stdin, skip ahead to the run or Popen sections. If you want to execute complex shell commands, see the note on shell=True at the end of this answer.
The check_output function works in all officially maintained versions of Python. But for more recent versions, a more flexible approach is available.
Modern versions of Python (3.5 or higher): run
If you're using Python 3.5+, and do not need backwards compatibility, the new run function is recommended by the official documentation for most tasks. It provides a very general, high-level API for the subprocess module. To capture the output of a program, pass the subprocess.PIPE flag to the stdout keyword argument. Then access the stdout attribute of the returned CompletedProcess object:
>>> import subprocess
>>> result = subprocess.run(['ls', '-l'], stdout=subprocess.PIPE)
>>> result.stdout
b'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
The return value is a bytes object, so if you want a proper string, you'll need to decode it. Assuming the called process returns a UTF-8-encoded string:
>>> result.stdout.decode('utf-8')
'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
This can all be compressed to a one-liner if desired:
>>> subprocess.run(['ls', '-l'], stdout=subprocess.PIPE).stdout.decode('utf-8')
'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
If you want to pass input to the process's stdin, you can pass a bytes object to the input keyword argument:
>>> cmd = ['awk', 'length($0) > 5']
>>> ip = 'foo\nfoofoo\n'.encode('utf-8')
>>> result = subprocess.run(cmd, stdout=subprocess.PIPE, input=ip)
>>> result.stdout.decode('utf-8')
'foofoo\n'
You can capture errors by passing stderr=subprocess.PIPE (capture to result.stderr) or stderr=subprocess.STDOUT (capture to result.stdout along with regular output). If you want run to throw an exception when the process returns a nonzero exit code, you can pass check=True. (Or you can check the returncode attribute of result above.) When security is not a concern, you can also run more complex shell commands by passing shell=True as described at the end of this answer.
Later versions of Python streamline the above further. In Python 3.7+, the above one-liner can be spelled like this:
>>> subprocess.run(['ls', '-l'], capture_output=True, text=True).stdout
'total 0\n-rw-r--r-- 1 memyself staff 0 Mar 14 11:04 files\n'
Using run this way adds just a bit of complexity, compared to the old way of doing things. But now you can do almost anything you need to do with the run function alone.
Older versions of Python (3-3.4): more about check_output
If you are using an older version of Python, or need modest backwards compatibility, you can use the check_output function as briefly described above. It has been available since Python 2.7.
subprocess.check_output(*popenargs, **kwargs)
It takes takes the same arguments as Popen (see below), and returns a string containing the program's output. The beginning of this answer has a more detailed usage example. In Python 3.5+, check_output is equivalent to executing run with check=True and stdout=PIPE, and returning just the stdout attribute.
You can pass stderr=subprocess.STDOUT to ensure that error messages are included in the returned output. When security is not a concern, you can also run more complex shell commands by passing shell=True as described at the end of this answer.
If you need to pipe from stderr or pass input to the process, check_output won't be up to the task. See the Popen examples below in that case.
Complex applications and legacy versions of Python (2.6 and below): Popen
If you need deep backwards compatibility, or if you need more sophisticated functionality than check_output or run provide, you'll have to work directly with Popen objects, which encapsulate the low-level API for subprocesses.
The Popen constructor accepts either a single command without arguments, or a list containing a command as its first item, followed by any number of arguments, each as a separate item in the list. shlex.split can help parse strings into appropriately formatted lists. Popen objects also accept a host of different arguments for process IO management and low-level configuration.
To send input and capture output, communicate is almost always the preferred method. As in:
output = subprocess.Popen(["mycmd", "myarg"],
stdout=subprocess.PIPE).communicate()[0]
Or
>>> import subprocess
>>> p = subprocess.Popen(['ls', '-a'], stdout=subprocess.PIPE,
... stderr=subprocess.PIPE)
>>> out, err = p.communicate()
>>> print out
.
..
foo
If you set stdin=PIPE, communicate also allows you to pass data to the process via stdin:
>>> cmd = ['awk', 'length($0) > 5']
>>> p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
... stderr=subprocess.PIPE,
... stdin=subprocess.PIPE)
>>> out, err = p.communicate('foo\nfoofoo\n')
>>> print out
foofoo
Note Aaron Hall's answer, which indicates that on some systems, you may need to set stdout, stderr, and stdin all to PIPE (or DEVNULL) to get communicate to work at all.
In some rare cases, you may need complex, real-time output capturing. Vartec's answer suggests a way forward, but methods other than communicate are prone to deadlocks if not used carefully.
As with all the above functions, when security is not a concern, you can run more complex shell commands by passing shell=True.
Notes
1. Running shell commands: the shell=True argument
Normally, each call to run, check_output, or the Popen constructor executes a single program. That means no fancy bash-style pipes. If you want to run complex shell commands, you can pass shell=True, which all three functions support. For example:
>>> subprocess.check_output('cat books/* | wc', shell=True, text=True)
' 1299377 17005208 101299376\n'
However, doing this raises security concerns. If you're doing anything more than light scripting, you might be better off calling each process separately, and passing the output from each as an input to the next, via
run(cmd, [stdout=etc...], input=other_output)
Or
Popen(cmd, [stdout=etc...]).communicate(other_output)
The temptation to directly connect pipes is strong; resist it. Otherwise, you'll likely see deadlocks or have to do hacky things like this.
This is way easier, but only works on Unix (including Cygwin) and Python2.7.
import commands
print commands.getstatusoutput('wc -l file')
It returns a tuple with the (return_value, output).
For a solution that works in both Python2 and Python3, use the subprocess module instead:
from subprocess import Popen, PIPE
output = Popen(["date"],stdout=PIPE)
response = output.communicate()
print response
I had the same problem but figured out a very simple way of doing this:
import subprocess
output = subprocess.getoutput("ls -l")
print(output)
Note: This solution is Python3 specific as subprocess.getoutput() doesn't work in Python2
Something like that:
def runProcess(exe):
p = subprocess.Popen(exe, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
while(True):
# returns None while subprocess is running
retcode = p.poll()
line = p.stdout.readline()
yield line
if retcode is not None:
break
Note, that I'm redirecting stderr to stdout, it might not be exactly what you want, but I want error messages also.
This function yields line by line as they come (normally you'd have to wait for subprocess to finish to get the output as a whole).
For your case the usage would be:
for line in runProcess('mysqladmin create test -uroot -pmysqladmin12'.split()):
print line,
This is a tricky but super simple solution which works in many situations:
import os
os.system('sample_cmd > tmp')
print(open('tmp', 'r').read())
A temporary file(here is tmp) is created with the output of the command and you can read from it your desired output.
Extra note from the comments:
You can remove the tmp file in the case of one-time job. If you need to do this several times, there is no need to delete the tmp.
os.remove('tmp')
Vartec's answer doesn't read all lines, so I made a version that did:
def run_command(command):
p = subprocess.Popen(command,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT)
return iter(p.stdout.readline, b'')
Usage is the same as the accepted answer:
command = 'mysqladmin create test -uroot -pmysqladmin12'.split()
for line in run_command(command):
print(line)
You can use following commands to run any shell command. I have used them on ubuntu.
import os
os.popen('your command here').read()
Note: This is deprecated since python 2.6. Now you must use subprocess.Popen. Below is the example
import subprocess
p = subprocess.Popen("Your command", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()[0]
print p.split("\n")
I had a slightly different flavor of the same problem with the following requirements:
Capture and return STDOUT messages as they accumulate in the STDOUT buffer (i.e. in realtime).
#vartec solved this Pythonically with his use of generators and the 'yield'
keyword above
Print all STDOUT lines (even if process exits before STDOUT buffer can be fully read)
Don't waste CPU cycles polling the process at high-frequency
Check the return code of the subprocess
Print STDERR (separate from STDOUT) if we get a non-zero error return code.
I've combined and tweaked previous answers to come up with the following:
import subprocess
from time import sleep
def run_command(command):
p = subprocess.Popen(command,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
shell=True)
# Read stdout from subprocess until the buffer is empty !
for line in iter(p.stdout.readline, b''):
if line: # Don't print blank lines
yield line
# This ensures the process has completed, AND sets the 'returncode' attr
while p.poll() is None:
sleep(.1) #Don't waste CPU-cycles
# Empty STDERR buffer
err = p.stderr.read()
if p.returncode != 0:
# The run_command() function is responsible for logging STDERR
print("Error: " + str(err))
This code would be executed the same as previous answers:
for line in run_command(cmd):
print(line)
Your Mileage May Vary, I attempted #senderle's spin on Vartec's solution in Windows on Python 2.6.5, but I was getting errors, and no other solutions worked. My error was: WindowsError: [Error 6] The handle is invalid.
I found that I had to assign PIPE to every handle to get it to return the output I expected - the following worked for me.
import subprocess
def run_command(cmd):
"""given shell command, returns communication tuple of stdout and stderr"""
return subprocess.Popen(cmd,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
stdin=subprocess.PIPE).communicate()
and call like this, ([0] gets the first element of the tuple, stdout):
run_command('tracert 11.1.0.1')[0]
After learning more, I believe I need these pipe arguments because I'm working on a custom system that uses different handles, so I had to directly control all the std's.
To stop console popups (with Windows), do this:
def run_command(cmd):
"""given shell command, returns communication tuple of stdout and stderr"""
# instantiate a startupinfo obj:
startupinfo = subprocess.STARTUPINFO()
# set the use show window flag, might make conditional on being in Windows:
startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
# pass as the startupinfo keyword argument:
return subprocess.Popen(cmd,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
stdin=subprocess.PIPE,
startupinfo=startupinfo).communicate()
run_command('tracert 11.1.0.1')
On Python 3.7+, use subprocess.run and pass capture_output=True:
import subprocess
result = subprocess.run(['echo', 'hello', 'world'], capture_output=True)
print(repr(result.stdout))
This will return bytes:
b'hello world\n'
If you want it to convert the bytes to a string, add text=True:
result = subprocess.run(['echo', 'hello', 'world'], capture_output=True, text=True)
print(repr(result.stdout))
This will read the bytes using your default encoding:
'hello world\n'
If you need to manually specify a different encoding, use encoding="your encoding" instead of text=True:
result = subprocess.run(['echo', 'hello', 'world'], capture_output=True, encoding="utf8")
print(repr(result.stdout))
Splitting the initial command for the subprocess might be tricky and cumbersome.
Use shlex.split() to help yourself out.
Sample command
git log -n 5 --since "5 years ago" --until "2 year ago"
The code
from subprocess import check_output
from shlex import split
res = check_output(split('git log -n 5 --since "5 years ago" --until "2 year ago"'))
print(res)
>>> b'commit 7696ab087a163e084d6870bb4e5e4d4198bdc61a\nAuthor: Artur Barseghyan...'
Without shlex.split() the code would look as follows
res = check_output([
'git',
'log',
'-n',
'5',
'--since',
'5 years ago',
'--until',
'2 year ago'
])
print(res)
>>> b'commit 7696ab087a163e084d6870bb4e5e4d4198bdc61a\nAuthor: Artur Barseghyan...'
Here a solution, working if you want to print output while process is running or not.
I added the current working directory also, it was useful to me more than once.
Hoping the solution will help someone :).
import subprocess
def run_command(cmd_and_args, print_constantly=False, cwd=None):
"""Runs a system command.
:param cmd_and_args: the command to run with or without a Pipe (|).
:param print_constantly: If True then the output is logged in continuous until the command ended.
:param cwd: the current working directory (the directory from which you will like to execute the command)
:return: - a tuple containing the return code, the stdout and the stderr of the command
"""
output = []
process = subprocess.Popen(cmd_and_args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=cwd)
while True:
next_line = process.stdout.readline()
if next_line:
output.append(str(next_line))
if print_constantly:
print(next_line)
elif not process.poll():
break
error = process.communicate()[1]
return process.returncode, '\n'.join(output), error
For some reason, this one works on Python 2.7 and you only need to import os!
import os
def bash(command):
output = os.popen(command).read()
return output
print_me = bash('ls -l')
print(print_me)
If you need to run a shell command on multiple files, this did the trick for me.
import os
import subprocess
# Define a function for running commands and capturing stdout line by line
# (Modified from Vartec's solution because it wasn't printing all lines)
def runProcess(exe):
p = subprocess.Popen(exe, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
return iter(p.stdout.readline, b'')
# Get all filenames in working directory
for filename in os.listdir('./'):
# This command will be run on each file
cmd = 'nm ' + filename
# Run the command and capture the output line by line.
for line in runProcess(cmd.split()):
# Eliminate leading and trailing whitespace
line.strip()
# Split the output
output = line.split()
# Filter the output and print relevant lines
if len(output) > 2:
if ((output[2] == 'set_program_name')):
print filename
print line
Edit: Just saw Max Persson's solution with J.F. Sebastian's suggestion. Went ahead and incorporated that.
According to #senderle, if you use python3.6 like me:
def sh(cmd, input=""):
rst = subprocess.run(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, input=input.encode("utf-8"))
assert rst.returncode == 0, rst.stderr.decode("utf-8")
return rst.stdout.decode("utf-8")
sh("ls -a")
Will act exactly like you run the command in bash
Improvement for better logging.
For better output you can use iterator.
From below, we get better
from subprocess import Popen, getstatusoutput, PIPE
def shell_command(cmd):
result = Popen(cmd, shell=True, stdout=PIPE, stderr=PIPE)
output = iter(result.stdout.readline, b'')
error = iter(result.stderr.readline, b'')
print("##### OutPut ###")
for line in output:
print(line.decode("utf-8"))
print("###### Error ########")
for line in error:
print(error.decode("utf-8")) # Convert bytes to str
status, terminal_output = run_command(cmd)
print(terminal_output)
shell_command("ls") # this will display all the files & folders in directory
Other method using getstatusoutput ( Easy to understand)
from subprocess import Popen, getstatusoutput, PIPE
status_Code, output = getstausoutput(command)
print(output) # this will give the terminal output
# status_code, output = getstatusoutput("ls") # this will print the all files & folder available in the directory
If you use the subprocess python module, you are able to handle the STDOUT, STDERR and return code of command separately. You can see an example for the complete command caller implementation. Of course you can extend it with try..except if you want.
The below function returns the STDOUT, STDERR and Return code so you can handle them in the other script.
import subprocess
def command_caller(command=None)
sp = subprocess.Popen(command, stderr=subprocess.PIPE, stdout=subprocess.PIPE, shell=False)
out, err = sp.communicate()
if sp.returncode:
print(
"Return code: %(ret_code)s Error message: %(err_msg)s"
% {"ret_code": sp.returncode, "err_msg": err}
)
return sp.returncode, out, err
I would like to suggest simppl as an option for consideration. It is a module that is available via pypi: pip install simppl and was runs on python3.
simppl allows the user to run shell commands and read the output from the screen.
The developers suggest three types of use cases:
The simplest usage will look like this:
from simppl.simple_pipeline import SimplePipeline
sp = SimplePipeline(start=0, end=100):
sp.print_and_run('<YOUR_FIRST_OS_COMMAND>')
sp.print_and_run('<YOUR_SECOND_OS_COMMAND>') ```
To run multiple commands concurrently use:
commands = ['<YOUR_FIRST_OS_COMMAND>', '<YOUR_SECOND_OS_COMMAND>']
max_number_of_processes = 4
sp.run_parallel(commands, max_number_of_processes) ```
Finally, if your project uses the cli module, you can run directly another command_line_tool as part of a pipeline. The other tool will
be run from the same process, but it will appear from the logs as
another command in the pipeline. This enables smoother debugging and
refactoring of tools calling other tools.
from example_module import example_tool
sp.print_and_run_clt(example_tool.run, ['first_number', 'second_nmber'],
{'-key1': 'val1', '-key2': 'val2'},
{'--flag'}) ```
Note that the printing to STDOUT/STDERR is via python's logging module.
Here is a complete code to show how simppl works:
import logging
from logging.config import dictConfig
logging_config = dict(
version = 1,
formatters = {
'f': {'format':
'%(asctime)s %(name)-12s %(levelname)-8s %(message)s'}
},
handlers = {
'h': {'class': 'logging.StreamHandler',
'formatter': 'f',
'level': logging.DEBUG}
},
root = {
'handlers': ['h'],
'level': logging.DEBUG,
},
)
dictConfig(logging_config)
from simppl.simple_pipeline import SimplePipeline
sp = SimplePipeline(0, 100)
sp.print_and_run('ls')
Here is a simple and flexible solution that works on a variety of OS versions, and both Python 2 and 3, using IPython in shell mode:
from IPython.terminal.embed import InteractiveShellEmbed
my_shell = InteractiveShellEmbed()
result = my_shell.getoutput("echo hello world")
print(result)
Out: ['hello world']
It has a couple of advantages
It only requires an IPython install, so you don't really need to worry about your specific Python or OS version when using it, it comes with Jupyter - which has a wide range of support
It takes a simple string by default - so no need to use shell mode arg or string splitting, making it slightly cleaner IMO
It also makes it cleaner to easily substitute variables or even entire Python commands in the string itself
To demonstrate:
var = "hello world "
result = my_shell.getoutput("echo {var*2}")
print(result)
Out: ['hello world hello world']
Just wanted to give you an extra option, especially if you already have Jupyter installed
Naturally, if you are in an actual Jupyter notebook as opposed to a .py script you can also always do:
result = !echo hello world
print(result)
To accomplish the same.
The output can be redirected to a text file and then read it back.
import subprocess
import os
import tempfile
def execute_to_file(command):
"""
This function execute the command
and pass its output to a tempfile then read it back
It is usefull for process that deploy child process
"""
temp_file = tempfile.NamedTemporaryFile(delete=False)
temp_file.close()
path = temp_file.name
command = command + " > " + path
proc = subprocess.run(command, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
if proc.stderr:
# if command failed return
os.unlink(path)
return
with open(path, 'r') as f:
data = f.read()
os.unlink(path)
return data
if __name__ == "__main__":
path = "Somepath"
command = 'ecls.exe /files ' + path
print(execute(command))
eg, execute('ls -ahl')
differentiated three/four possible returns and OS platforms:
no output, but run successfully
output empty line, run successfully
run failed
output something, run successfully
function below
def execute(cmd, output=True, DEBUG_MODE=False):
"""Executes a bash command.
(cmd, output=True)
output: whether print shell output to screen, only affects screen display, does not affect returned values
return: ...regardless of output=True/False...
returns shell output as a list with each elment is a line of string (whitespace stripped both sides) from output
could be
[], ie, len()=0 --> no output;
[''] --> output empty line;
None --> error occured, see below
if error ocurs, returns None (ie, is None), print out the error message to screen
"""
if not DEBUG_MODE:
print "Command: " + cmd
# https://stackoverflow.com/a/40139101/2292993
def _execute_cmd(cmd):
if os.name == 'nt' or platform.system() == 'Windows':
# set stdin, out, err all to PIPE to get results (other than None) after run the Popen() instance
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
else:
# Use bash; the default is sh
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True, executable="/bin/bash")
# the Popen() instance starts running once instantiated (??)
# additionally, communicate(), or poll() and wait process to terminate
# communicate() accepts optional input as stdin to the pipe (requires setting stdin=subprocess.PIPE above), return out, err as tuple
# if communicate(), the results are buffered in memory
# Read stdout from subprocess until the buffer is empty !
# if error occurs, the stdout is '', which means the below loop is essentially skipped
# A prefix of 'b' or 'B' is ignored in Python 2;
# it indicates that the literal should become a bytes literal in Python 3
# (e.g. when code is automatically converted with 2to3).
# return iter(p.stdout.readline, b'')
for line in iter(p.stdout.readline, b''):
# # Windows has \r\n, Unix has \n, Old mac has \r
# if line not in ['','\n','\r','\r\n']: # Don't print blank lines
yield line
while p.poll() is None:
sleep(.1) #Don't waste CPU-cycles
# Empty STDERR buffer
err = p.stderr.read()
if p.returncode != 0:
# responsible for logging STDERR
print("Error: " + str(err))
yield None
out = []
for line in _execute_cmd(cmd):
# error did not occur earlier
if line is not None:
# trailing comma to avoid a newline (by print itself) being printed
if output: print line,
out.append(line.strip())
else:
# error occured earlier
out = None
return out
else:
print "Simulation! The command is " + cmd
print ""
This question already has answers here:
Store output of subprocess.Popen call in a string [duplicate]
(15 answers)
Closed 4 years ago.
How can I get the output of a process run using subprocess.call()?
Passing a StringIO.StringIO object to stdout gives this error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 444, in call
return Popen(*popenargs, **kwargs).wait()
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 588, in __init__
errread, errwrite) = self._get_handles(stdin, stdout, stderr)
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 945, in _get_handles
c2pwrite = stdout.fileno()
AttributeError: StringIO instance has no attribute 'fileno'
>>>
If you have Python version >= 2.7, you can use subprocess.check_output which basically does exactly what you want (it returns standard output as string).
Simple example (linux version, see note):
import subprocess
print subprocess.check_output(["ping", "-c", "1", "8.8.8.8"])
Note that the ping command is using linux notation (-c for count). If you try this on Windows remember to change it to -n for same result.
As commented below you can find a more detailed explanation in this other answer.
Output from subprocess.call() should only be redirected to files.
You should use subprocess.Popen() instead. Then you can pass subprocess.PIPE for the stderr, stdout, and/or stdin parameters and read from the pipes by using the communicate() method:
from subprocess import Popen, PIPE
p = Popen(['program', 'arg1'], stdin=PIPE, stdout=PIPE, stderr=PIPE)
output, err = p.communicate(b"input data that is passed to subprocess' stdin")
rc = p.returncode
The reasoning is that the file-like object used by subprocess.call() must have a real file descriptor, and thus implement the fileno() method. Just using any file-like object won't do the trick.
See here for more info.
For python 3.5+ it is recommended that you use the run function from the subprocess module. This returns a CompletedProcess object, from which you can easily obtain the output as well as return code.
from subprocess import PIPE, run
command = ['echo', 'hello']
result = run(command, stdout=PIPE, stderr=PIPE, universal_newlines=True)
print(result.returncode, result.stdout, result.stderr)
I have the following solution. It captures the exit code, the stdout, and the stderr too of the executed external command:
import shlex
from subprocess import Popen, PIPE
def get_exitcode_stdout_stderr(cmd):
"""
Execute the external command and get its exitcode, stdout and stderr.
"""
args = shlex.split(cmd)
proc = Popen(args, stdout=PIPE, stderr=PIPE)
out, err = proc.communicate()
exitcode = proc.returncode
#
return exitcode, out, err
cmd = "..." # arbitrary external command, e.g. "python mytest.py"
exitcode, out, err = get_exitcode_stdout_stderr(cmd)
I also have a blog post on it here.
Edit: the solution was updated to a newer one that doesn't need to write to temp. files.
I recently just figured out how to do this, and here's some example code from a current project of mine:
#Getting the random picture.
#First find all pictures:
import shlex, subprocess
cmd = 'find ../Pictures/ -regex ".*\(JPG\|NEF\|jpg\)" '
#cmd = raw_input("shell:")
args = shlex.split(cmd)
output,error = subprocess.Popen(args,stdout = subprocess.PIPE, stderr= subprocess.PIPE).communicate()
#Another way to get output
#output = subprocess.Popen(args,stdout = subprocess.PIPE).stdout
ber = raw_input("search complete, display results?")
print output
#... and on to the selection process ...
You now have the output of the command stored in the variable "output". "stdout = subprocess.PIPE" tells the class to create a file object named 'stdout' from within Popen. The communicate() method, from what I can tell, just acts as a convenient way to return a tuple of the output and the errors from the process you've run. Also, the process is run when instantiating Popen.
The key is to use the function subprocess.check_output
For example, the following function captures stdout and stderr of the process and returns that as well as whether or not the call succeeded. It is Python 2 and 3 compatible:
from subprocess import check_output, CalledProcessError, STDOUT
def system_call(command):
"""
params:
command: list of strings, ex. `["ls", "-l"]`
returns: output, success
"""
try:
output = check_output(command, stderr=STDOUT).decode()
success = True
except CalledProcessError as e:
output = e.output.decode()
success = False
return output, success
output, success = system_call(["ls", "-l"])
If you want to pass commands as strings rather than arrays, use this version:
from subprocess import check_output, CalledProcessError, STDOUT
import shlex
def system_call(command):
"""
params:
command: string, ex. `"ls -l"`
returns: output, success
"""
command = shlex.split(command)
try:
output = check_output(command, stderr=STDOUT).decode()
success = True
except CalledProcessError as e:
output = e.output.decode()
success = False
return output, success
output, success = system_call("ls -l")
In Ipython shell:
In [8]: import subprocess
In [9]: s=subprocess.check_output(["echo", "Hello World!"])
In [10]: s
Out[10]: 'Hello World!\n'
Based on sargue's answer. Credit to sargue.
This question already has answers here:
Store output of subprocess.Popen call in a string [duplicate]
(15 answers)
Closed 4 years ago.
How can I get the output of a process run using subprocess.call()?
Passing a StringIO.StringIO object to stdout gives this error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 444, in call
return Popen(*popenargs, **kwargs).wait()
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 588, in __init__
errread, errwrite) = self._get_handles(stdin, stdout, stderr)
File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 945, in _get_handles
c2pwrite = stdout.fileno()
AttributeError: StringIO instance has no attribute 'fileno'
>>>
If you have Python version >= 2.7, you can use subprocess.check_output which basically does exactly what you want (it returns standard output as string).
Simple example (linux version, see note):
import subprocess
print subprocess.check_output(["ping", "-c", "1", "8.8.8.8"])
Note that the ping command is using linux notation (-c for count). If you try this on Windows remember to change it to -n for same result.
As commented below you can find a more detailed explanation in this other answer.
Output from subprocess.call() should only be redirected to files.
You should use subprocess.Popen() instead. Then you can pass subprocess.PIPE for the stderr, stdout, and/or stdin parameters and read from the pipes by using the communicate() method:
from subprocess import Popen, PIPE
p = Popen(['program', 'arg1'], stdin=PIPE, stdout=PIPE, stderr=PIPE)
output, err = p.communicate(b"input data that is passed to subprocess' stdin")
rc = p.returncode
The reasoning is that the file-like object used by subprocess.call() must have a real file descriptor, and thus implement the fileno() method. Just using any file-like object won't do the trick.
See here for more info.
For python 3.5+ it is recommended that you use the run function from the subprocess module. This returns a CompletedProcess object, from which you can easily obtain the output as well as return code.
from subprocess import PIPE, run
command = ['echo', 'hello']
result = run(command, stdout=PIPE, stderr=PIPE, universal_newlines=True)
print(result.returncode, result.stdout, result.stderr)
I have the following solution. It captures the exit code, the stdout, and the stderr too of the executed external command:
import shlex
from subprocess import Popen, PIPE
def get_exitcode_stdout_stderr(cmd):
"""
Execute the external command and get its exitcode, stdout and stderr.
"""
args = shlex.split(cmd)
proc = Popen(args, stdout=PIPE, stderr=PIPE)
out, err = proc.communicate()
exitcode = proc.returncode
#
return exitcode, out, err
cmd = "..." # arbitrary external command, e.g. "python mytest.py"
exitcode, out, err = get_exitcode_stdout_stderr(cmd)
I also have a blog post on it here.
Edit: the solution was updated to a newer one that doesn't need to write to temp. files.
I recently just figured out how to do this, and here's some example code from a current project of mine:
#Getting the random picture.
#First find all pictures:
import shlex, subprocess
cmd = 'find ../Pictures/ -regex ".*\(JPG\|NEF\|jpg\)" '
#cmd = raw_input("shell:")
args = shlex.split(cmd)
output,error = subprocess.Popen(args,stdout = subprocess.PIPE, stderr= subprocess.PIPE).communicate()
#Another way to get output
#output = subprocess.Popen(args,stdout = subprocess.PIPE).stdout
ber = raw_input("search complete, display results?")
print output
#... and on to the selection process ...
You now have the output of the command stored in the variable "output". "stdout = subprocess.PIPE" tells the class to create a file object named 'stdout' from within Popen. The communicate() method, from what I can tell, just acts as a convenient way to return a tuple of the output and the errors from the process you've run. Also, the process is run when instantiating Popen.
The key is to use the function subprocess.check_output
For example, the following function captures stdout and stderr of the process and returns that as well as whether or not the call succeeded. It is Python 2 and 3 compatible:
from subprocess import check_output, CalledProcessError, STDOUT
def system_call(command):
"""
params:
command: list of strings, ex. `["ls", "-l"]`
returns: output, success
"""
try:
output = check_output(command, stderr=STDOUT).decode()
success = True
except CalledProcessError as e:
output = e.output.decode()
success = False
return output, success
output, success = system_call(["ls", "-l"])
If you want to pass commands as strings rather than arrays, use this version:
from subprocess import check_output, CalledProcessError, STDOUT
import shlex
def system_call(command):
"""
params:
command: string, ex. `"ls -l"`
returns: output, success
"""
command = shlex.split(command)
try:
output = check_output(command, stderr=STDOUT).decode()
success = True
except CalledProcessError as e:
output = e.output.decode()
success = False
return output, success
output, success = system_call("ls -l")
In Ipython shell:
In [8]: import subprocess
In [9]: s=subprocess.check_output(["echo", "Hello World!"])
In [10]: s
Out[10]: 'Hello World!\n'
Based on sargue's answer. Credit to sargue.