CODEWITHSUNDEEP
pythonunixcronparamiko
Rohit
Rohit

Reputation: 189

How to edit crontab file present in the remote UNIX server using Python

I am having a crontab entry in my Python code describing which script should be scheduled in the UNIX remote server at the specified time.

I am writing a Python script which will connect to the ssh using Paramiko, it will go to the specified crontab file path in the remote server -> open the crontab file -> add the crontab entry specified in the Python script at the end of the file (on the new line) -> save & exit the crontab file.

Please let me know how I can achieve this.

P.S. : I already know how to connect to the server using Paramiko. Just stucked at the file handling part in the remote server.

Upvotes: 0

Views: 7461

Answers (2)

Jaguar
Jaguar

Reputation: 116

crontab -l 2>/dev/null| cat - <(echo "your new crontab entry here") | crontab -

Explanation

crontab -l

Outputs the current crontab to stdout.

2>/dev/null

[Optional] Supresses error messages from crontab -l. You'll get an error message if there is no crontab entry for the user. But that's not a problem.

cat - <(echo "your crontab entry here")

The - takes the input from the pipe (crontab -l) and uses it as the first thing to cat. Then the rest appends your new crontab entry to stdout. The <() syntax takes the output of the command inside and stores it in a temporary file.

crontab -

This sets the crontab entry to the stdin (which, thanks to the pipe, is all the stdout from the previous commands.)

Edit: It looks like you'll need to wrap the command with bash -c in order to get the pipes to work. See this stackoverflow entry.

Or, you can send a series of commands to paramiko. Just beware of concurrency.

crontab -l > /tmp/current.cron
echo "your crontab entry here" >> /tmp/current.cron
crontab /tmp/current.cron

Another alternative is:

crontab <(cat <(crontab -l 2>/dev/null) <(echo "your new crontab entry"))

Upvotes: 2

trojek
trojek

Reputation: 3228

I don't know exactly how Paramiko works but if you could use shell you can just simply execute:

echo "new line" >> cron_file

This command will add a string new line as a new line to the file cron_file.

Upvotes: 0

Related Questions