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Cron mechanism
Cron allows the system to perform a specified work at a specified time, and we can use the CRONTAB directive to manage the cron mechanism
Crontab parameters
-U: This parameter allows us to edit other people's crontab, if not add this parameter, will open their own crontab
Linux crontab command, the minimum execution time is one minute. If you need to repeat in less than one minute, there are two ways to implement it.
1. Use delay to implement every n seconds
Create a PHP to do the action, very simple, is to write the current time log.
CRONTAB-E Enter the following statement, and t
First, crontab-e Add output log*/1 * * * */qiwen_list/upload_to_hdfs.sh >/qiwen_list/mapred.log 2>1Second, check log found that Hadoop is not foundIii. specify Hadoop full path in the script#!/bin/sh#upload List to HDFsyesterday= ' Date--date= ' 1 day ago ' +%y%m%d 'Echo $yesterday/home/hadoop/bin/hadoop fs-put/qiwen_list/qiwen_${yesterday}.csv/qiwen_listExecute again, problem solved.Crontab in the shell every min
Example of a scheduled task using django-crontab, and django-crontab
Today, I plan to add a scheduled task in my Django application to regularly execute some regular check functions. So I thought that using the django-crontab plug-in can satisfy my needs, the following describes how to use this plug-in.
First, use pip
Crontab format and detailed example format: *** command indicates that the 1st column of the day-month-week command indicates minute 1 ~ 59 every minute, use * or */1 to indicate 2nd columns to indicate hour 1 ~ 23 (0 indicates 0 points) column 3rd indicates date 1 ~ 31 column 4th indicates the month 1 ~ 12 5th columns
Basic Format:* *** CommandHour, day, month, and week commands
The 1st column indicates minute 1 ~ 59. Each minute is represented by * or */1.The first column indicates the hour 1 ~ 23 (0 indicates 0 points)The 3rd column indicates the date 1 ~ 31The 4th column indicates the month 1 ~ 12The Identification Number of column 5th is from day of the week to day ~ 6 (0 indicates Sunday)6th columns of commands to r
Basic Format:
* *** Command
Hour, day, month, and week commands
The 1st column indicates minute 1 ~ 59. Each minute is represented by * or */1.
The first column indicates the hour 1 ~ 23 (0 indicates 0 points)
The 3rd column indicates the date 1 ~ 31
The 4th column indicates the month 1 ~ 12
The Identification Number of column 5th is from day of the week to day ~ 6 (0 indicates Sunday)
6th columns of comman
Format:* *** CommandHour, day, month, and week commands
The 1st column indicates minute 1 ~ 59. Each minute is represented by * or */1.The first column indicates the hour 1 ~ 23 (0 indicates 0 points)The 3rd column indicates the date 1 ~ 31The 4th column indicates the month 1 ~ 12The Identification Number of column 5th is from day of the week to day ~ 6 (0 indicates Sunday)6th columns of commands to run
Linux crontab Command Format and example
Linux crontab Command Format and example
Run */5 * every five minutes ****
0 *** per hour ****
Execute 0 0 every day ***
Execute 0 0 every week ** 0
0 0 1 per month **
Execute 0 0 1 1 * every year *
For detailed usage, refer
1. RoleYou can use the
SESSION and COOKIE are required by each interviewer, so I hope that you can deeply learn and understand this part to gain a better job opportunity.Go to laruence blog (this is a good place to learn PHP, click http://www.laruence.com for details /)During the interview, I often asked a question: "How do I set a 30-minute overdue Session ?", Don't think it looks simple. There is a lot of knowledge here, which is especially suitable for you to check wheth
Session and Cookie is every interviewer must ask the knowledge point, so hope that students can learn to understand this part to get better job opportunities the following content to the Laruence blog (this is a good place to learn PHP, details click http://www.laruence.com/) in my interview, I often ask a question: "How to set a 30-minute session expired?", we do not think that seemingly simple, here bread contains a lot of knowledge, especially
program called composer to manage the dependencies of various libraries, so if you have composer installed on your machine, you can skip this step, if not installed, You can install the latest version of composer with the following command.
$CD symfony-sample
$curl-ss https://getcomposer.org/installer | php
If you want to know more about composer, you can refer to this website.
After the installation completes composer, we can begin to install the current version of the Symfony2
indicate the source and the original linkCrontab file Format:Minute hour day month weekday username commandminute: Minute, value is 0-59Hour: Hour with a value of 1-23Day: Days with a value of 1-31Month: The value is 1-12Weekday: Week, value 0-6 (0 for Sunday, 1 for Monday, etc.)Username: The user to execute the program is generally set to rootCommand: Program path to execute (set to absolute path) for example
1. Whether the query is installed: Rpm-qa|grep cron
2. Install Crontab:
[Root@centos ~]# Yum Install Vixie-cron
[Root@centos ~]# Yum Install Crontabs
Description
Vixie-cron packages are Cron's main programs;
The Crontabs package is a program used to install, uninstall, or enumerate the tables used to drive the cron daemon.
3. Start and close this cron service in the following ways:
/sbin/service crond Start//boot service
/sbin/service Crond Stop//Off
First, open the command line. If crontab is not installed,
1, first install crontab:
Yum Install Crontabs
Description
/sbin/service crond Start//boot service/sbin/service Crond Stop//Off service/sbin/service crond Restart//Restart service/sbin/service Crond Reload//Reload Configuration/sbin/service crond Status//view current Crond run status
2, log on to the Linux system with ordinary users. Run Crond
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