Task scheduling--9.5 jobs on Linux

1. Task Plan Categories:

Perform a task at a time in the future: at, Batch

To perform a task periodically: crontab

1. e-Mail Service:

Smtp:simple Mail Transmission protocol

/var/spool/mail/username

Pop3:post Office Protocol

Imap4:internet Mail Access Protocol

1. 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]

  
  

1. AT command:

• To host a job that runs in the future time:

• Support for using job queue: default to a queue;

• Ctrl+d Submitting Jobs

• Format: 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

5.batch: using at for command execution, the system chooses to run the specified task when the resource is more idle;

6. Crontab Recurring Mission Plan

6.1 Daemon:crond, monitoring whether a task arrives at a point in time

6.2 Recurring tasks are available in two categories:

(1) System cron task; There is no default running user identity, so you need to specify the additional runner;/etc/crontab

Basic format:

# 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

Format:

# 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;

6.3 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;

6.4 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;

6.5 Complementary Tools : Anacron:

6.6 Note:

(1) If you do not want to receive notification messages for task execution results:

normal results not received : COMMAND >/dev/null

all results are not received : COMMAND &>/dev/null

(2) for crontab file,% has a special function, if the command will appear in the%, remember to escape, or use single quotation marks to its reference;

(3) Crontab's path variable is not exactly the same as the user's variable, so it is recommended that the task in cron use an absolute path

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;

[email protected] ~]# which Cpalias cp= ' cp-i '/bin/cp[[email protected] ~]# Crontab-eno crontab for root-using an empt Y onecrontab:installing new Crontab[[email protected] ~]# CRONTAB-L20 3 * * 1-6/bin/cp/etc//backups/etc-' Date +%Y-%m- %d '/

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

2 * * 1-6/bin/cp/etc/fstab/backups/fstab-' date +%y-%m-%d-%h-%m-%s '/

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;

0 0 * * */bin/echo ========== >>/statistics/meminfo.txt &&/bin/egrep ' ^s|^m '/proc/meminfo >>/stati Stics/meminfo.txt

Task scheduling--9.5 jobs on Linux