I have a running python program (on Amazon linux server). This program was started by crontab.
How can I view its content stdout without stopping it?
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2 Answers
You could just read the proc filesystem :
tail -f /proc/28897/fd/1
28897 is the process id.
You can get the process id using ps
For instance : ps aux | grep myScript.py
5 Comments
Loïc
Have you given the right process id ? Which command are you talking about ?
Ngo Thanh Nhan
command "tail -f /proc/<my process id>/fd/1". I use "print" in my python program
Loïc
this should definitively work that's weird, maybe try /fd/2
Oliver Baumann
Are you sure your program is in a state where it should be outputting messages?
tailing on a file descriptor won't give you any old messages, it will only print new ones. Consider either writing to a file via docs.python.org/2/library/…, or use shell redirection via ./foo.py >> bar.txt and then run tail -f bar.txt from a terminalNgo Thanh Nhan
redirect to a file works for me. Thanks Oliver Baumann and Loic
Elaborating on Loïc's answer:
The "1" at the end of tail -f /proc/28897/fd/1 denotes the stream you want to look into. 0 is STDIN, 1 is STDOUT, 2 is STDERR (https://en.wikipedia.org/wiki/File_descriptor)
Adding this as it can be quite cryptic to understand the black magic behind FDs, and as I don't have enough rep to comment ;-)