I'm trying to use ffmpeg from python. The command I need to execute is:
ffmpeg -i test_file-1kB.mp4 -i test_file.mp4 -filter_complex psnr="stats_file=test_file.mp4-1kB.psnr" -f null -
However, my output that is getting passed to subprocess looks like it is escaping the double quotes with backslashes like so:
In[1]: print(subprocess.list2cmdline(psnr_args))
ffmpeg -i test_file-1kB.mp4 -i test_file.mp4 -filter_complex psnr=\"stats_file=test_file.mp4-1kB.psnr\" -f null -
To use subprocess, I build my command line arguments one at a time into a list and then pass the list to subprocess.
psnr_args = []
psnr_args.append("ffmpeg")
#add first input, the encoded video
psnr_args.append("-i")
psnr_args.append(full_output_file_name)
#add second input, the original video
psnr_args.append("-i")
psnr_args.append(video_file)
#Setup the psnr log file
psnr_args.append("-filter_complex")
psnr_args.append('psnr="stats_file=%s.psnr"' % vstats_abs_filename )
#Output the video to null
psnr_args.append("-f")
psnr_args.append("null")
psnr_args.append("-")
print(subprocess.list2cmdline(psnr_args))
run_info_psnr = subprocess.run(psnr_args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
After more fiddling, I found a solution that works in this case but may not work in all cases. If I use double quotes as the outer quotes and the single quotes as the inner quotes, the output to subprocess uses a single quote at the same location with no backslash. This is acceptable for ffmpeg. However, for others where double quotes are the only solution, it won't be a fix.
psnr_args.append("psnr='stats_file=%s.psnr'" % vstats_abs_filename )
Output to subprocess looks like this:
In[1]: print(subprocess.list2cmdline(psnr_args))
ffmpeg -i test_file-1kB.mp4 -i test_file.mp4 -filter_complex psnr='stats_file=test_file.mp4-1kB.psnr' -f null -
In shell, the argument:
psnr="stats_file=test_file.mp4-1kB.psnr"
Is absolutely identical to:
psnr=stats_file=test_file.mp4-1kB.psnr
The quotes are removed during the shell's own processing. They are not part of the command passed to ffmpeg, which doesn't expect or understand them. Because you're directly telling the Python subprocess module to invoke a literal argument vector, there's no shell involved, so shell syntax shouldn't be present.
This has something to do with ffmpeg AV filter chain syntax too. You need to run the command like xxxx -filter_complex "psnr='stats.txt'" xxxx. To get this, you should ensure the double quote that encapsulate the filter chain reaches inside. subproces expects a flat list as the first argument, where the command is the first entry. So ['ffmpeg', '-i', "t1.mp4", "-filter_compelx", '"psnr=\'stats.txt\'"', .... and so on ].
Related
I would like to be able to call some executables that take in parameters and then dump the output to a file. I've attempted to use both os.system and subprocess calls to no avail. Here is a sample of what I'd like python to execute for me...
c:\directory\executable_program.exe -f w:\directory\input_file.txt > Z\directory\output_file.txt
Notice the absolute paths as I will be traversing hundreds of various directories to act on files etc..
Many thanks ahead of time!
Some examples that I've tried:
subprocess.run(['c:\directory\executable_program.exe -f w:\directory\input_file.txt > Z\directory\output_file.txt']
subprocess.call(r'"c:\directory\executable_program.exe -f w:\directory\input_file.txt > Z\directory\output_file.txt"']
subprocess.call(r'"c:\directory\executable_program.exe" -f "w:\directory\input_file.txt > Z\directory\output_file.txt"']
Your attempts contain various amounts of quoting errors.
subprocess.run(r'c:\directory\executable_program.exe -f w:\directory\input_file.txt > Z\directory\output_file.txt', shell=True)
should work, where the r prefix protects the backslashes from being interpreted and removed by Python before the subprocess runs, and the absence of [...] around the value passes it verbatim to the shell (hence, shell=True).
On Windows you could get away with putting the command in square brackets even though it's not a list, and omitting shell=True in some circumstances.
If you wanted to avoid the shell, try
with open(r'Z\directory\output_file.txt', 'wb') as dest:
subprocess.run(
[r'c:\directory\executable_program.exe', '-f', r'w:\directory\input_file.txt'],
stdout=dest)
which also illustrates how to properly pass a list of strings in square brackets as the first argument to subprocess.run.
I have a string, which is a framed command that should be executed by in command line
cmdToExecute = "TRAPTOOL -a STRING "ABC" -o STRING 'XYZ'"
I am considering the string to have the entire command that should be triggered from command prompt. If you take a closer look at the string cmdToExecute, you can see the option o with value XYZ enclosed in SINGLE QUOTE. There is a reason that this needs to be given in single quote orelse my tool TRAPTOOL will not be able to process the command.
I am using subprocess.Popen to execute the entire command. Before executing my command in a shell, I am printing the content
print "Cmd to be exectued: %r" % cmdToExecute
myProcess = subprocess.Popen(cmdToExecute, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=False)
(stdOut, stdErr) = myProcess.communicate()
The output of the above command is,
Cmd to be executed: TRAPTOOL -a STRING "ABC" -o \'XYZ\'.
You can see that the output shows a BACKWARD SLASH added automatically while printing. Actually, the \ is not there in the string, which I tested using a regex. But, when the script is run on my box, the TRAPTOOL truncates the part of the string XYZ on the receiving server. I manually copy pasted the print output and tried sending it, I saw the same error on the receiving server. However, when I removed the backward slash, it sent the trap without any truncation.
Can anyone say why this happens?
Is there anyway where we can see what command is actually executed in subprocess.Popen?
Is there any other way I can execute my command other that subprocess.Popen that might solve this problem?
Try using shlex to split your command string:
>>> import shlex
>>> argv = shlex.split("TRAPTOOL -a STRING \"ABC\" -o STRING 'XYZ'")
>>> myProcess = subprocess.Popen(argv, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=False)
>>> (stdOut, stdErr) = myProcess.communicate()
The first parameter to the Popen constructor can be an argument list for your shell command or a string, but an argument list might be easier to work with because of all the quotes involved. (See the Python subprocess documentation.)
If you want to see the commands being written, you could probably do something like:
>>> argv = shlex.split("bash -x -c 'TRAPTOOL -a STRING \"ABC\" -o STRING \'XYZ\''")
This makes bash echo the commands to the shell by means of the -x option.
You asked for the repr representation of the string, not the str representation. Basically, what would you have to type at the Python interactive interpreter to get the same output? That's what %r displays. Change that to %s to see the value as it's actually stored:
print "Cmd to be exectued: %s" % cmdToExecute
I am trying to develop a script to read pcap file and extract some field from it but using tshark as a subprocess. However i am getting syntax error regarding cmd. Can anyone help me out on this?
def srcDestDport (filename):
cmd = r"tshark -o column.format:"Source","%s", "Destination","%d", "dstport"," %uD"' -r %s"%(filename)
subcmd = cmd.split(' ')
lines = subprocess.Popen(subcmd,stdout=subprocess.PIPE)
return lines
As far as Python is concerned, you appear to be missing some commas in your cmd definition:
cmd = r"tshark -o column.format:"Source","%s", "Destination","%d", "dstport"," %uD"' -r %s"%(filename)
# -- no comma here -^ ----^ ----^ --^
because the first string ends when the first " is encountered at "Source"; a raw string does not preclude you from escaping embedded quotes.
If you wanted to produce a list of arguments, just make it a list directly, saves you interpolating the filename too:
cmd = ["tshark", "-o",
'column.format:"Source","%s","Destination","%d","dstport"," %uD"',
"-r", filename]
Note the single quotes around the 3rd argument to preserve the quotes in the command line argument.
This eliminates the need to split as well and preserves whitespace in the filename.
I've been trying to pass a command that works only with literal double quotes in the commandline around the "concat:file1|file2" argument for ffmpeg.
I cant however make this work from python with subprocess.Popen(). Anyone have an idea how one passes quotes into subprocess.Popen?
Here is the code:
command = "ffmpeg -i "concat:1.ts|2.ts" -vcodec copy -acodec copy temp.mp4"
output,error = subprocess.Popen(command, universal_newlines=True,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE).communicate()
When I do this, ffmpeg won't take it any other way other than quotes around the concat segement. Is there a way to successfully pass this line to subprocess.Popen command?
I'd suggest using the list form of invocation rather than the quoted string version:
command = ["ffmpeg", "-i", "concat:1.ts|2.ts", "-vcodec", "copy",
"-acodec", "copy", "temp.mp4"]
output,error = subprocess.Popen(
command, universal_newlines=True,
stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
This more accurately represents the exact set of parameters that are going to be passed to the end process and eliminates the need to mess around with shell quoting.
That said, if you absolutely want to use the plain string version, just use different quotes (and shell=True):
command = 'ffmpeg -i "concat:1.ts|2.ts" -vcodec copy -acodec copy temp.mp4'
output,error = subprocess.Popen(
command, universal_newlines=True, shell=True,
stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
Either use single quotes 'around the "whole pattern"' to automatically escape the doubles or explicitly "escape the \"double quotes\"". Your problem has nothing to do with Popen as such.
Just for the record, I had a problem particularly with a list-based command passed to Popen that would not preserve proper double quotes around a glob pattern (i.e. what was suggested in the accepted answer) under Windows. Joining the list into a string with ' '.join(cmd) before passing it to Popen solved the problem.
This works with python 2.7.3 The command to pipe stderr to stdout has changed since older versions of python:
Put this in a file called test.py:
#!/usr/bin/python
import subprocess
command = 'php -r "echo gethostname();"'
p = subprocess.Popen(command, universal_newlines=True, shell=True,
stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
text = p.stdout.read()
retcode = p.wait()
print text
Invoke it:
python test.py
It prints my hostname, which is apollo:
apollo
Read up on the manual for subprocess: http://docs.python.org/2/library/subprocess.html
I have been working with a similar issue, with running a relatively complex
command over ssh. It also had multiple double quotes and single quotes. Because
I was piping the command through python, ssh, powershell etc.
If you can instead just convert the command into a shell script, and run the
shell script through subprocess.call/Popen/run, these issues will go away.
So depending on whether you are on windows or on linux or mac, put the
following in a shell script either (script.sh or script.bat)
ffmpeg -i "concat:1.ts|2.ts" -vcodec copy -acodec copy temp.mp4
Then you can run
import subprocess; subprocess.call(`./script.sh`; shell=True)
Without having to worry about single quotes, etc.
This line of code in your question isn't valid Python syntax:
command = "ffmpeg -i "concat:1.ts|2.ts" -vcodec copy -acodec copy temp.mp4"
If you had a Python file with just this line in it, you would get a syntax error. A string literal surrounded with double quotes can't have double quotes in them unless they are escaped with a backslash. So you could fix that line by replacing it with:
command = "ffmpeg -i \"concat:1.ts|2.ts\" -vcodec copy -acodec copy temp.mp4"
Another way to fix this line is to use single quotes for the string literal in Python, that way Python is not confused when the string itself contains a double quote:
command = 'ffmpeg -i "concat:1.ts|2.ts" -vcodec copy -acodec copy temp.mp4'
Once you have fixed the syntax error, you can then tackle the issue with using subprocess, as explained in this answer. I also wrote this answer to explain a helpful mental model for subprocess in general.
Also struggling with a string argument containing spaces and not wanting to use the shell=True.
The solution was to use double quotes for the inside strings.
args = ['salt', '-G', 'environment:DEV', 'grains.setvals', '{"man_version": "man-dev-2.3"}']
try:
p = subprocess.Popen(args, stdin=subprocess.PIPE
, stdout=subprocess.PIPE
, stderr=subprocess.PIPE
)
(stdin,stderr) = p.communicate()
except (subprocess.CalledProcessError, OSError ) as err:
exit(1)
if p.returncode != 0:
print("Failure in returncode of command:")
Anybody suffering from this pain. It also works with params enclosed with quotation marks.
params = ["ls", "-la"]
subprocess.check_output(" ".join(params), shell=True)
I am trying to call the following curl command with python:
curl -k -F file=#something.zip -F "data={\\"title\\":\\"Another App\\"}" -Lu usr:pwd https://build.phonegap.com/api/v0/apps
For it to work, I've found that the json I'm passing in data needs to be escaped with backslashes.
I can call this command with...
os.system(curl -k -F file=#something.zip -F "data={\\"title\\":\\"Another App\\"}" -Lu usr:pwd https://build.phonegap.com/api/v0/apps)
and it works.
However, when I try to use the subprocess module like this...
s = 'curl -k -F file=#something.zip -F "data={\\"title\\":\\"Another App\\"}" -Lu usr:pwd https://build.phonegap.com/api/v0/apps'
push = subprocess.Popen(s.split(), stdout=subprocess.PIPE, stderr=subprocess.PIPE)
output, errors = push.communicate()
print output
...the curl doesn't work and I get an error from the api I'm using that I'm using invalid parameters, which I've gotten in the past when I've used improperly escaped json.
What is going on here? Why can I call this command with os.system and not subprocess.Popen? So far my hypothesis is that the split is messing up something in the string, but I didn't find anything that looked wrong when I check the output of s.split().
perhaps using shell=True
push = subprocess.Popen(s, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
Instead of doing
s.split()
try using shlex from the standard library
import shlex
shlex.split(s)
Shlex allows you configure the escaping behavior (see the link for details, the defaults might be sufficient though)
Specifically where you are going wrong is splitting at:
\"Another,
App\"}"
.split()#
is using space-character by default you'll need to change split behaviour as others have said.