Execute Python script via crontab


I’m trying to execute a Python script using the Linux crontab. I want to run this script every 10 minutes.

I found a lot of solutions and none of them worked. For example: edit the anacron at /etc/cron.d or use crontab -e. I put this line at the end of the file, but it doesn’t change anything. Do I have to restart any service(s)?

*/2 * * * * /usr/bin/python /home/souza/Documets/Listener/listener.py

What file must I edit to configure this?

Here is the script.

# -*- coding: iso-8859-15 -*-

import json
import os
import pycurl
import sys
import cStringIO

if __name__ == "__main__":

    name_server_standart = "Server created by script %d"
    json_file_standart = "{ "server" : {  "name" : "%s", "imageRef" : "%s", "flavorRef" : "%s" } }"

    curl_auth_token = pycurl.Curl()

    gettoken = cStringIO.StringIO()

    curl_auth_token.setopt(pycurl.URL, "")
    curl_auth_token.setopt(pycurl.POST, 1)
    curl_auth_token.setopt(pycurl.HTTPHEADER, ["X-Auth-User: cpca",
                          "X-Auth-Key: 438ac2d9-689f-4c50-9d00-c2883cfd38d0"])

    curl_auth_token.setopt(pycurl.HEADERFUNCTION, gettoken.write)
    chg = gettoken.getvalue()

    auth_token = chg[chg.find("X-Auth-Token: ")+len("X-Auth-Token: ") : chg.find("X-Server-Management-Url:")-1]

    token = "X-Auth-Token: {0}".format(auth_token)


    getter = cStringIO.StringIO()
    curl_hab_image = pycurl.Curl()
    curl_hab_image.setopt(pycurl.URL, "")
    curl_hab_image.setopt(pycurl.HTTPGET, 1) #tirei essa linha e funcionou, nao sei porque
    curl_hab_image.setopt(pycurl.HTTPHEADER, [token])

    curl_hab_image.setopt(pycurl.WRITEFUNCTION, getter.write)
    #curl_list.setopt(pycurl.VERBOSE, 1)

    getter = cStringIO.StringIO()

    curl_list = pycurl.Curl()
    curl_list.setopt(pycurl.URL, "")
    curl_list.setopt(pycurl.HTTPGET, 1) #tirei essa linha e funcionou, nao sei porque
    curl_list.setopt(pycurl.HTTPHEADER, [token])

    curl_list.setopt(pycurl.WRITEFUNCTION, getter.write)
    #curl_list.setopt(pycurl.VERBOSE, 1)


    resp = getter.getvalue()

    con = int(resp.count("status"))

    s = json.loads(resp)

    lst = []

    for i in range(con):

    for j in range(len(lst)):
        actual = lst.pop()
        print actual

        if actual != "ACTIVE" and actual != "BUILD" and actual != "REBOOT" and actual != "RESIZE":

            print "Entra no If"

            f = file('counter', 'r+w')

            num = 0
            for line in f:
                num = line

            content = int(num)+1

            ins = str(content)


            print "Contador"

            json_file = file('json_file_create_server.json','r+w')

            name_server_final = name_server_standart % content
            path_to_image = ""
            path_to_flavor = ""

            new_json_file_content = json_file_standart % (name_server_final, path_to_image, path_to_flavor)


            print "Json File"

            fil = file("json_file_create_server.json")
            siz = os.path.getsize("json_file_create_server.json")

            cont_size = "Content-Length: %d" % siz
            cont_type = "Content-Type: application/json"
            accept = "Accept: application/json"

            c_create_servers = pycurl.Curl()

            logger = cStringIO.StringIO()

            c_create_servers.setopt(pycurl.URL, "")

            c_create_servers.setopt(pycurl.HTTPHEADER, [token, cont_type, accept, cont_size])

            c_create_servers.setopt(pycurl.POST, 1)

            c_create_servers.setopt(pycurl.INFILE, fil)

            c_create_servers.setopt(pycurl.INFILESIZE, siz)

            c_create_servers.setopt(pycurl.WRITEFUNCTION, logger.write)

            print "Teste perform"


            print logger.getvalue()

Asked By: guisantogui



Just use crontab -e and follow the tutorial here.

Look at point 3 for a guide on how to specify the frequency.

Based on your requirement, it should effectively be:

*/10 * * * * /usr/bin/python script.py
Answered By: Raul Marengo

Put your script in a file foo.py starting with


Then give execute permission to that script using

chmod a+x foo.py

and use the full path of your foo.py file in your crontab.

See documentation of execve(2) which is handling the shebang.

As you have mentioned it doesn’t change anything.

First, you should redirect both standard input and standard error from the crontab execution like below:

*/2 * * * * /usr/bin/python /home/souza/Documets/Listener/listener.py > /tmp/listener.log 2>&1

Then you can view the file /tmp/listener.log to see if the script executed as you expected.

Second, I guess what you mean by change anything is by watching the files created by your program:

f = file('counter', 'r+w')
json_file = file('json_file_create_server.json', 'r+w')

The crontab job above won’t create these file in directory /home/souza/Documets/Listener, as the cron job is not executed in this directory, and you use relative path in the program. So to create this file in directory /home/souza/Documets/Listener, the following cron job will do the trick:

*/2 * * * * cd /home/souza/Documets/Listener && /usr/bin/python listener.py > /tmp/listener.log 2>&1

Change to the working directory and execute the script from there, and then you can view the files created in place.

Answered By: greenqy
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