CODEWITHSUNDEEP
pythonlinuxbash
user1689987
user1689987

Reputation: 1546

Why is my Python script not writing to file when it is backgrounded it in Linux?

I can do:

python script.py > logfile 2>&1

and once I kill it using ctrl c I can see changes to the logfile. However, when I do:

python script.py > logfile 2>&1 &

I can't see any changes to the log file . How can I background my script and still have it write to the logfile?

Upvotes: 7

Views: 3358

Answers (2)

lam vu Nguyen
lam vu Nguyen

Reputation: 631

command 2> error.txt 1> output.txt this worked for me, more in https://linuxize.com/post/bash-redirect-stderr-stdout/

I find it diffcult to understand why command > logfile 2>&1 did not work

Upvotes: 0

Charles Duffy
Charles Duffy

Reputation: 295413

Your writes aren't going into the ether -- they're getting buffered. After a graceful shutdown (SIGTERM, not SIGKILL), you should see content in the file then as well.

Alternately, you can explicitly flush:

sys.stdout.flush()

...or tell Python to run in unbuffered mode:

python -u yourscript.py

or start your script with

#!/usr/bin/python -u

...to ensure that content is written. This will, of course, have a performance penalty, since your script will be trying to perform IO more frequently.

(As an aside, #!/usr/bin/env python -u is not guaranteed to work: Only a command name and a single argument are guaranteed to be passed through from a shebang line to a command that's run; your operating system may or may not honor more than that).

Upvotes: 11

Related Questions