Summarize your own 8 tips used in shell command line

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The shell is the command interpreter.

See which shells are supported by this system

1 Tab Command completion

This can be used almost every time, for example, I have a file called file.txt, if only one file name in this directory starts with F, then I enter F and then tab will automatically fill out file.txt

22 Shortcut keys

Ctrl+l Clear Screen

Ctrl+u Clear a row (the part before the cursor)

3 Command aliases

Alias: View the current alias

Define a new alias, which defines the alias to delete the directory Xrm

Of course, this definition is just a temporary definition and is not written to the file, and is re-alias after each reboot.

Can speak a custom alias written in configuration file ~/.BASHRC

Remove an alias with Unalias

4. Input and output redirection

is to write the output to another place, or to get an input from a place

Output redirection:

[Email protected] ~]# ls-l >>/dev/null

Redirect the output to/dev/null, where you can understand that/dev/null is a black hole, and redirects here are not printed.

Symbol >> is empty the original content and then write

Symbol > is appended at the end of the original content

Input redirect

Symbols <

/dev/tty This file is often used to redirect to a terminal, which is useful for input

Read Password </dev/tty reading password from terminal

For example, I want to broadcast the contents of file.txt.

Error output redirection, redirect only when an error is encountered

The usual processing is to generate the relevant log file

For example, when backing up a server file, it is often selected when the after midnight server has very little access, and you are still dreaming, so it is important to redirect the wrong information. So the next day you go to work, just look at the wrong files and know what's wrong.

Cp–r/usr/backup/2>/bak.error

5 Piping

A pipeline is one output that is used as another input, often in step processing

For example

LS-/etc |more; paging through the contents of a file Ls–l/etc | grep init; Extract ls–l/etc with command execution results | grep init | Wc–l; where WC is used to calculate how many rows

Here's a brief explanation of the WC command.

The WC command is used to count the number of lines, the number of words, the number of characters

WC #会依次输出 Number of lines, number of words, and number of characters

Wc-l #行数

wc-w# number of words

Wc-c #字符个数

6 Command Connector

&& the previous command executes successfully and the latter command executes

|| The previous command failed to execute after a command was executed

7 Command Substitution symbols

On the top of the Keyboard tab. • Note that it is not a quotation mark

When a command substitution symbol is encountered, the statement in the command substitution symbol is executed as a command, and the result is returned to the previous layer

8 reading the beginning or end of a file

Head-n file first few lines

Tail-n file files after several lines

Tail-f file continuously observes the end of a document and is suitable for dynamic observation of the log file

Of course, we can also work with grep to view only the log information that contains the specified characters

Finally, attach the previously written link to the awk,grep,sed

grep command Detailed-9 Classic usage scenarios

SED command detailed

awk Command Quick Start

Summarize your own 8 tips used in shell command line