Here's my code to execute a jar file in Python:
import os
os.system("java -jar xyz.jar")
I can see the output on terminal, but want to store it in a file. How can I do that?
2 Answers
With subprocess.call you can pipe outputs (stdout, stderr or both) directly into file:
import subprocess
subprocess.call("java -jar xyz.jar", shell=True, stdout=open('outfile.txt', 'wt'), stderr=subprocess.STDOUT)
Note that I added shell=True parameter, which is required if your application requires shell-specific variables (such as where Java is located).
Also note that in the above call, the output streams are handled as follows:
- stderr stream is piped to stdout, and
- stdout is piped to outfile
More details on stream configurations are available in subprocess manual page.
9 Comments
dev
I tried, but output file is empty. But I can still see output on terminal. Where I might be doing wrong?
dev
No, I'm just doing this.
jsalonen
Wait... I get it now. Your application is probably printing to stderr so you need to pipe stderr stream to the file too.
jsalonen
Check out the edited answer, which takes stderr into account.
jsalonen
Update after a chat: In this case
shell=True was actually required to correctly locate Java. |
Don't use os.system, use subprocess instead.
import subprocess
output = subprocess.check_output(["java", "-jar", "xyz.jar"])
file = open('file.txt', 'w+')
file.write(output)
file.close()
2 Comments
dev
I get this error: File "pythonScript.py", line 4, in <module> output = subprocess.check_output("java -jar xyz.jar")
dev
Traceback (most recent call last): File "pythonScript.py", line 2, in <module> output = subprocess.check_output("java -jar xyz.jar") File "/usr/lib/python3.4/subprocess.py", line 603, in check_output with Popen(*popenargs, stdout=PIPE, **kwargs) as process: File "/usr/lib/python3.4/subprocess.py", line 848, in init restore_signals, start_new_session) File "/usr/lib/python3.4/subprocess.py", line 1446, in _execute_child raise child_exception_type(errno_num, err_msg) FileNotFoundError: [Errno 2] No such file or directory: 'java -jar xyz.jar'
>?