Python Learning record--ubuntu (iv) Scheduled Tasks, grep, regular expressions

I. crontab for scheduling tasks :

1. Parameters

(1)-u User: Used to set a user's crontab service

(2)-e: Edit the contents of a user's crontab file. If you do not specify a user, the crontab file for the current user is edited

(3)-L: Displays the contents of a user's crontab file, or displays the contents of the current user's crontab file if no user is specified

(4)-R: Delete a user's crontab file from the/var/spool/cron directory, or delete the current user's crontab file by default if no user is specified

(5)-I: give confirmation prompt when deleting user's crontab file

2. Format:* indicates the week 0~7 (where Sunday can be expressed in 0 or 7) * indicates the month 1~12 * represents the date 1~31 * indicates the hour 1~23 (0 means 0 points) * indicates minutes 1~59 Each xx with * or */1 represents the pre-execute command (do not exceed 64 bytes, if exceeded, write the file after the command: "/bin/bash (Specify absolute path, environment variable can continue to execute) file name" or at the beginning of the file #! /bin/bash then use./execute)

Two. grep is used to find content:

1. Format

grep parameter search for content file name

2. Parameters

(1)-C--count #计算符合样式的列数

(2)-L--file-with-matches #列出文件内容符合指定的样式的文件名称.

(3)-V--revert-match #显示不包含匹配文本的所有行.

(4)-I--ignore-case #忽略字符大小写的差别.

(5)-O # Show only keywords that match

(6)-N # Display line number

(7)-e #使用正则表达式

Three. Regular Expressions:

1. Symbolic Meaning:

(1) ^: match the beginning, put in [] to indicate the inverse, such as [^0-9] represents all non-digital

(2) $: Match End

(3) []: Range Matching

(4) [A-z]: matches all lowercase letters

(5) [A-z]: matches all uppercase letters

(6) [0-9]: Match all numbers

(7). : Matches a single character

(8) *: Indicates that the preceding content (adjacent) appears 0 or more times

(9) +: Indicates that the preceding content (adjacent) appears 1 or more times

(10)? Said the preceding content (adjacent) appears 0 or 1 times

Python Learning record--ubuntu (iv) Scheduled Tasks, grep, regular expressions