How do I push a subprocess.call() output to terminal and file?
I have subprocess.call(["ddrescue", in_file_path, out_file_path], stdout=drclog)
. I'd like this to display the ddrescue in the terminal as it's running and write the output to the file drclog. I've tried using subprocess.call(["ddrescue", in_file_path, out_file_path], stdout=drclog, shell=True)
, but that gives me an input error into ddrescue.
Solution 1:
If ddrescue
doesn't change its output if its stdout/stderr are redirected to a pipe then you could use tee
utility, to display output on the terminal and to save it to a file:
$ ddrescue input_path output_path ddrescue_logfile |& tee logfile
If it does then you could try to provide a pseudo-tty using script
utility:
$ script -c 'ddrescue input_path output_path ddrescue_logfile' -q logfile
If it writes directly to a terminal then you could use screen
to capture the output:
$ screen -L -- ddrescue input_path output_path ddrescue_logfile
The output is saved in screenlog.0
file by default.
To emulate the tee
-based command in Python without calling tee
utility:
#!/usr/bin/env python3
import shlex
import sys
from subprocess import Popen, PIPE, STDOUT
command = 'ddrescue input_path output_path ddrescue_logfile'
with Popen(shlex.split(command), stdout=PIPE, stderr=STDOUT, bufsize=1) as p:
with open('logfile', 'wb') as logfile:
for line in p.stdout:
logfile.write(line)
sys.stdout.buffer.write(line)
sys.stdout.buffer.flush()
To call the tee
-based command in Python using shell=True
:
#!/usr/bin/env python
from pipes import quote
from subprocess import call
files = input_path, output_path, ddrescue_logfile
rc = call('ddrescue {} | tee -a drclog'.format(' '.join(map(quote, files))),
shell=True)
To emulate the script
-based command:
#!/usr/bin/env python3
import os
import shlex
import pty
logfile = open('logfile', 'wb')
def read(fd):
data = os.read(fd, 1024) # doesn't block, it may return less
logfile.write(data) # it can block but usually not for long
return data
command = 'ddrescue input_path output_path ddrescue_logfile'
status = pty.spawn(shlex.split(command), read)
logfile.close()
To call screen
command in Python:
#!/usr/bin/env python3
import os
import shlex
from subprocess import check_call
screen_cmd = 'screen -L -- ddrescue input_path output_path ddrescue_logfile'
check_call(shlex.split(screen_cmd))
os.replace('screenlog.0', 'logfile')