Linux Learning Essay Nine

Knowledge of the main shell basics

Standing at the user's angle: Shell type

Logon Shell: Normal is usually a certain terminal sign-in

Su-username

Su-l USERNAME

Non-sign-on shell

Su Usernmae

Open Command Window under graphics terminal

Shell scripts that are executed automatically

Configuration file for Kash:

Global configuration:/etc/profile/etc/profile.d/*.sh

/etc/bashrc

Personal configuration: ~/.bash_profile, ~/.BASHRC

Function:

File for Profile class

Setting environment variables

Run a command or script

Files of the BASHRC class

Setting environment variables

Defining command aliases

Login Shell If you read the configuration file:

/etc/profile-->/ETC/PROFILE.D/*.SH-->~/.BASH_PROFILE-->/.BASHRC-->/ETC/BASHRC

Non-logon Shell if the configuration file:

~/.BASHRC-->/etc/bashrc-->/etc/profile.d/*.sh

We all know that the computer includes a controller (instruction), an arithmetic, a memory

Bus includes: Address bus (memory addressing), data bus (transmit data), Control Bus (Control command)

Register: CPU Ephemeral memory

I/O devices: hard drives, etc. input

Input device

Output device:

System settings: Default output device, standard output stdout,1

Default input device: standard input stoin,0

Standard error Output: stderp,2

I/O redirection:

>: Overwrite Output

>>: Append output

Example: LS var >>/tmp/var.out

Set-c prohibit overwrite redirection for already existing files, forcing overwrite redirection

Set +c turn off the above functions

Standard output and error output are not the same data stream

2>: Redirect Error output

2>>: Append method

such as: Ls/var >/tmp/var3.out 2>/tmp/err.out

Ls/var >/tmp/var4.out 2>/tmp/var4.out

&>: Redirect standard output or error output to the same file

&>>

<: Input redirection

<<:here Document

Eof:end of File =end

Cat >>/tmp/myfile.txt<<eof generating files in scripts

Pipeline: The output of the previous command as input to the latter command

Command 1| Command 2| command 3| ....

Example: echo "Hello World" |tr ' A-Z ' A-Z '

echo "Redhat" |passwd--stdin Hive

cut-d:-f3/etc/passwd |sort-n

Tee: Save and display

echo "Hello,world" |tee/tmp/hello.out

Wc-l/etc/passwd |cut-d '-f1

Ls-l/usr/bin/head-1

Cut-d:-f1/etc/passwd/sort-n

Head-6/etc/inittab |tail-1

Tail-9/etc/passwd |head-1|cut-d:-f1,7|tee/tmp/users

Ls-d/etc/pa*|wc-l

echo "Alias Cls=clear" >>~/.BASHRC

Need for File lookup: grep, Egrep, Fgrep

grep: Search for text according to pattern, and conform to pattern text display

Pattern: (pattern) text Word wildcards regular the expression's meta-character combination to match the condition

I: Ignore case

V: Show rows that are not matched by pattern

--color Display Color

-O: Displays only strings that are matched by the pattern

Alias grep= ' grep--color ' take aliases

Grep-o ' Root '/etc/passswd

Regular expression: Regular,expression,regexp

Metacharacters

. :

* :

.* :

\?:

\{m,n\}: Matches the preceding character at least m times, up to N times

\{1,\}, match its preceding characters at least 1 times, at most 0650) this.width=650; "src="/e/u261/themes/default/images/spacer.gif "style=" Background:url ("/e/u261/lang/zh-cn/images/localimage.png") no-repeat center;border:1px solid #ddd; "alt=" spacer.gif "/> Times

\{0,3\}: Match its preceding characters at least 0 times, up to 3 times

grep ' a \{1,3\}b ' text.txt

Location anchoring:

^: Anchor the beginning of the line, any content after this character must appear at the beginning of the line

grep ' ^r. Root '/etc/passwd

$: Anchor line end, any content of this character money must appear at the end of the row

^$: whitespace character

[]: matches any character in the specified range

[^]: matches any character outside the specified range

[:d Igit:] [: Lower:] [: Upper:] [:p UNCT:] [: Space:] [: Alpha:] [: Alnum:]

grep ' [[:d igit:]]$ '/etc/inittab

\< or \b: Anchor word, any character following it must appear as the first word

\> \b: Anchors the ending, any character preceding it must appear as the tail of the word

Group:

\(\)

\ (ab\) *:ab can occur 0 or more times

\1: Refers to the first opening parenthesis and all the contents of the corresponding closing parenthesis

\2: \ 3:

Regular Expressions: Includes the basic regular expression (REGEXP) extended Regular expression (EXTENDED REGEXP)

Basic Regular Expressions:

. :

[ ]:

[^ ]:

Number of matches:

*：

\?:

\{m,n\}:

.*:

Anchoring:

^:

$:

\< \b:

\> \b:

\(\):

\1,\2,\3 ...

grep: Filtering text commands using patterns defined by basic regular expressions

I

-V:

-O:

--color:

-E: Using extended regular expressions

-a#: Displays matching rows and rows following this line

-b#: Display matching rows and lines preceding this line

-c#: Displays matching rows and rows before and after this line

Grep-a 2 ' ^core ID '/proc/cpuinfo

To extend the regular expression:

Character Matching:

. [] [^] Same as basic expression

Number of matches:

* ？

+: Match its first character at least once

{M,n}

Location anchoring:

^ $ \< \>

Group:

(): Group

\1,\2,\3 ...

Or

|:or

such as: C|cat: Is it cat or cat or C or cat?

Grep-e ' c| Cat ' Test6.txt

Gerp--color-e ' C|cat ' test6.txt

grep--color-e ' (c|c) at ' Test6.txt

grep--color-e ' ^[[:space:]]+ '/boot/grub/grub.conf

Grep-e=egrep (supports extended regular expressions using commands)

If a number from 1 to 255 is displayed

Egrep--color ' \< ([1-9][1-9][0-9]|[ 0-9]2[0-4][0-9]25[0-5]>\> '/boot/grub/grub.conf

Show IP Address:

Ifconfig |egrep-o ' above. \>.\

\>1. | {3}

IP Address:

Class 5: A B C D E

a:1-127

b:128-191

c:192-223

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Linux Learning Essay Nine