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Connor Meeks
Connor Meeks

Reputation: 501

Using Crontab in a Python Script

I am trying to use the contents of a crontab inside a python script. I want to do everything using python. In the end I hope to take the contents of the crontab, convert it to a temporary textfile, read in the lines of the text file and manipulate it.

Is there any way i can use the contents of the crontab file and manipulate it as if it were a text file???

I've looked into the subprocess module but am not too sure if this is the right solution....

NOTE: I am not trying to edit the crontab in any way, I am just trying to read it in and manipulate it within my python code. In the end, the crontab will remain the same. I just need the information contained inside the crontab to mess with.

Upvotes: 0

Views: 550

Answers (2)

Mayank Diwedi
Mayank Diwedi

Reputation: 211

As you are trying to change the crontab entry (e.g.- deleting the completed tasks):

import os
import datetime
os.system("crontab -l > new")
read_file = open("new","r")
write_file = open("new_edit","w")
today= datetime.datetime.now()
current_date = today.day
current_month = today.month
for lines in read_file:
        if lines=="\n":
                pass
        else:
                sep = lines.split(" ")
                if (current_date < int(sep[2]) and current_month == int(sep[3])):
                        write_file.write(lines)
write_file.close()
os.system("sudo mv new_edit /var/spool/cron/ec2-user")

This code will help to delete the previous day tasks. I think this will help you.

Upvotes: 0

Wayne Werner
Wayne Werner

Reputation: 51907

If you were to try crontab -h, which is usually the help option, you'll get this:

$ crontab -h
crontab: invalid option -- 'h'
crontab: usage error: unrecognized option
Usage:
 crontab [options] file
 crontab [options]
 crontab -n [hostname]

Options:
 -u <user>  define user
 -e         edit user's crontab
 -l         list user's crontab
 -r         delete user's crontab
 -i         prompt before deleting
 -n <host>  set host in cluster to run users' crontabs
 -c         get host in cluster to run users' crontabs
 -x <mask>  enable debugging

Default operation is replace, per 1003.2

The line to note is the one that says -l list user's crontab. If you try that, you see that it lists out the contents of one's crontab file. Based on that, you can run the following:

import subprocess

crontab = subprocess.check_output(['crontab', '-l'])

And crontab will contain the contents of one's crontab. In Python3 it will return binary data so you'll need crontab = crontab.decode().

Upvotes: 2

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