September 5 Linux Task Schedule Job

Task Schedule:
Perform a task at a time in the future: at, Batch
To perform a task periodically: crontab

e-Mail Service:
Smtp:simple Mail Transmission protocol
/var/spool/mail/username

Pop3:post Office Protocol
Imap4:internet Mail Access Protocol

Mua:mail command

Mail command:

Mail: Enter the interactive email interface;
Mail-s ' SUBJECT ' [email protected]

Mail-s ' SUBJECT ' [email protected] </path/from/somefile

COMMAND | Mail-s ' SUBJECT ' [email protected]

AT command:

To host a job that runs in the future time:

Support for using job queues:
The default is a queue;

Ctrl+d

At [option] ... Time

Time:
(1) Absolute time
HH:MM,
Mmdd[cc]yy, Mm/dd/[cc]yy, dd.mm.[cc]yy or [cc]yy-mm-dd
Tomorrow
(2) Relative time
now+ #UNIT
Minute, hour, day, week
(3) Blur time
Midnight
Noon
Teatime

Common options:
-Q queue:at Job queue;
-f/path/from/somefile: Reads the job to be run from the specified file;
-L: View a list of such running jobs in the job queue; equivalent to using the ATQ command;
-C At_job_num: Look at the contents of the running job;
-D: Delete the specified job; equivalent to ATRM

Batch
The system chooses to run the specified task when the resource is more idle;

Crontab: Recurring Task Schedule
Daemon: Crond

There are two types of recurring tasks:
(1) System cron task; There is no default running user identity, so you need to specify the additional runner;
/etc/crontab

Vim command

# Example of Job definition:
#.----------------Minute (0-59)
# | .-------------Hour (0-23)
# |  | .----------Day of Month (1-31)
# |  |  | .-------month (1-12) OR jan,feb,mar,apr ...
# |  |  |  | .----Day of Week (0-6) (sunday=0 or 7) or Sun,mon,tue,wed,thu,fri,sat
# |  |  |  | |
# * * * * * * user-name command to be executed

7 fields:
Top 5 fields: Point in time
User-name: Run the task as a user
command to being executed: to run a task

(2) User Cron Task: Submitted by a user, the default is to run as the submitter, so there is no need to specify the additional runner;
/var/spool/cron/username

VIM command; not recommended
crontab Command: Recommended

# Example of Job definition:
#.----------------Minute (0-59)
# | .-------------Hour (0-23)
# |  | .----------Day of Month (1-31)
# |  |  | .-------month (1-12) OR jan,feb,mar,apr ...
# |  |  |  | .----Day of Week (0-6) (sunday=0 or 7) or Sun,mon,tue,wed,thu,fri,sat
# |  |  |  | |
# * * * * * command to be executed

5 Time points:
Minutes: valid value range 0-59;
Hours: 0-23
Day: 1-31
Month: 1-12
Weeks: 0-7

Note: The date of the month and the number of weeks, not recommended to use at the same time;

For example:
6 * * * *

Time notation:

*: Each time point in the valid value range of the time point;
-: A specific continuous time range, 3-7
,: A discrete point in time, 3,5,7
/#: The amount of time in a valid time frame, for specifying the frequency;
1-30/4, */4

5 */3 * * */bin/echo "howdy"

5 7 * * 1-5/bin/echo "Howdy"

crontab command:
crontab [-u user] [-l |-r |-e]
-u User: Not to manage your own cron task, but to specify the target user's cron task; Root has the ability to manage other users ' cron tasks; default management of their own;

-l:list, list the tasks;
-r:remove to remove all tasks;
-e:edit, edit, open a default editor for the current shell session to edit the cron task table;

Practice:
1, every Monday to Saturday 3:20 A.M., run the CP command to archive the/etc/directory, storage location is/BACKUPS/ETC-YYYY-MM-DD;

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2, every Sunday 2:30 A.M., run the CP command to backup the/etc/fstab file, the storage location is/BACKUP/FSTAB-YYYY-MM-DD-HH-MM-SS

650) this.width=650; "title=" 2.jpg "src=" Http://s3.51cto.com/wyfs02/M00/72/D9/wKiom1XuhkCwzidYAAA5Wrprf-k036.jpg " alt= "Wkiom1xuhkcwzidyaaa5wrprf-k036.jpg"/>

3, every night 12 o'clock, get all the lines in the/proc/meminfo file starting with S or M, appended to the/statistics/meminfo.txt file, and the daily message before, to add a similar =============== separator line;

650) this.width=650; "title=" 3.jpg "src=" Http://s3.51cto.com/wyfs02/M01/72/D9/wKiom1Xuhk6hGcQzAABXwpXTZ10619.jpg " alt= "Wkiom1xuhk6hgcqzaabxwpxtz10619.jpg"/>

September 5 Linux Task Schedule Job