Introduction to the Vim editor and bash arithmetic operations

Source: Internet
Author: User
Tags arithmetic arithmetic operators

(i) Vim last-line mode

  • Vim last-line mode: Built-in command-line interface
    • Address delimitation
      • Start_pos[,end_pos]
      • #: A specific # line, for example, 5 or line 5th
        • .: Indicates when the forward
        • $: Represents the last line, for example, $-1 means from the current line to the 2nd line
        • #,#: Specifies the row range, the left is the starting row, and the right side is the end row, for example 10,100 indicates a total of 91 rows from line 10th to line 100th
        • #,+#: Specifies the row range, the left is the starting row, the right side is the offset, for example 3,+7 means starting from line 3rd and the following 7 lines total 8 rows
        • %: Full text, equals 1,$
        • /pattern/: From the cursor position, the first line that is matched to the PATTERN, such as/pattern/,$, from the matching line to the last row
        • Can be used together with editing commands for editing operations
          • d/Delete, y/copy, c/Modify
          • There is no space in the middle, the edit command follows the address delimitation directly
          • W filename/content Save As
          • R filename/to merge another file in
    • Find
      • /pattern: Starting at the cursor, looking back at all the strings that were matched to the PATTERN, the cursor stops at the first matching string
      • ? Pattern: Starting at the cursor, looking forward to all the strings that have been pattern matched, the cursor stops at the first matching string
      • N: Next find result, same as command direction
      • N: Previous find result, opposite command direction
    • Find and replace
      • S/used to find/replace content/modifier
        • What to look for: regular expressions
        • What to replace: You cannot use regular expressions, but you can reference
          • If "What to look for" uses a grouping symbol in the pattern, you can use the latter reference \1,\2 in "What to replace" ...
          • or use the & symbol to directly refer to all the text that matches the content used to find
        • If the content itself has a/symbol, you need to add \ to escape
        • You can also change/change to other infrequently used characters so that the/symbol of the content itself does not need to be escaped, such as using the @ symbol, or the # symbol, etc.
        • Modifier
          • I: Ignore case (ignores case in find pattern)
          • G: Global substitution means that a row is replaced if it matches multiple times, and the first occurrence in each row is replaced by default
        • Example
          • 1,20s/this/this/g
          • %[email protected]\<t\ ([[: Alpha:]]\+\) \>@t\[email protected]: Converts words beginning with all lowercase t to words beginning with uppercase T in full text
          • %[email Protected]\<t[[:alpha:]]\+\>@&[email protected]: Adds ER to the word that starts all lowercase t in the full text
          • %[email protected]^#@@: Remove the # number in front of each line


1. Copy the/etc/grub2.cfg file to the/tmp directory and use the Find replacement command to delete the whitespace characters in front of all lines in the/tmp/grub2.cfg file





%[email Protected]^[[:space:]]\[email protected]@

2, copy the/etc/rc.d/init.d/functions file to the/tmp directory, and use the Find Replace command to add # to the beginning of each line in the/tmp/functions file that starts with a white space character

Answer:%[email protected]^[[:space:]]\+[^[:space:]]@#&@

3, add # to the beginning of the first three lines of the/tmp/grub2.cfg file

Answer: 1,3s/*/#&/

4, replace all enabled=0 in the/etc/yum.repos.d/centos-base.repo file with enabled=1, all gpgcheck=0 replaced by gpgcheck=1

Answer:%[email protected]\ (enabled\|gpgcheck\) [email protected]\[email protected]

  • VIM Multi-file mode
    • vim FILE1 FILE2 FILE3 ...
    • Switch between files: first/first file, last/last file, next/next file, previous/previous file
    • Save and exit all files: Wqall
    • save so file: Wall
    • exit All files: Qall
    • Multi-window
      • multi-file
        • -o: Horizontal separation, ctrl+w, press the up and down arrows after release, you can switch files; vim-o FILE1 FILE2 FILE3
        • -o: Vertical separation; ctrl+w, release and press left and right arrows to toggle file
      • Single file
        • ctrl+w, release and press S, split horizontal single file
        • Ctrl + W, release and press V, vertical separate single file
  • Customizing the working characteristics of vim
    • Command settings in the last-line mode, only valid for the current VIM process
    • If you want to permanently work, you need to modify the configuration file, just write the last command in the config file.
      • Global:/ETC/VIMRC
      • User personal: ~/.VIMRC, if the file does not exist, you need to create it yourself
    • Line number
      • Display: Set number or set Nu
      • Cancel: Set Nonumber or set Nonu
    • Parentheses match highlighting (seemingly vim has been highlighted now, the command is invalid >_<)
      • Display: Set Showmatch or set SM
      • Cancel: Set Noshowmatch or set NOSM
    • Auto Indent
      • Enable: Set AI
      • Disabled: Set Noai
    • Highlight search Results
      • Enabled: Set Hlsearch
      • Disabled: Set Nohlsearch
    • Syntax highlighting
      • Enabled: Syntax on
      • Disabled: Syntax off
    • Ignore character case
      • Enable: Set IC
      • Disabled: Set Noic
    • In the last-line mode, you can use the help command to get assistance, or help subject to get assistance with a topic, such as helping set

Job: If you set the TAB key to indent 4 characters, instead of 8

(ii) The arithmetic operations of Bash script programming

    • Arithmetic operators: +,-,*,/,**,%
    • Arithmetic operation format
      • Let var= arithmetic operation expression
      • $[arithmetic operation expression]
      • $ ((arithmetic operation expression))
      • Expr command
        • There should be spaces between each operand and operator
        • To get results, you need to use a command reference
    • Note: The multiplication symbol requires the use of escape characters in some scenarios

Exercise: Write a script that adds three users and asks for the sum of the UID of the three users

Introduction to the Vim editor and bash arithmetic operations

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