Linux Shell Learning Notes first day _ other

The following is a 1-2-day study of Shell learning notes

————————-I'm the separator —————————

Hardware to perform, operating between the kernel and the hardware.

The command parser.

Component elements of a shell script

1. System commands
   
2. Text Processing tools (sort, grep, sed, awk ...) ）
   
3. Variable
   
4. Conditional judgment
   
5. Circular structure
   
6. Function
   
   Shell Scripts Center (SSC)
   

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Non-negative Grep/awk

Few days. Statistical WC

Sort sorting sort|head/sed
Field Handles awk

Data Area Judge Awk |WC

Display text: echo [options] Text

-N Do not wrap lines

-E Resolution escape character

A issued a warning tone

c Finally, no line-wrapping symbol

F Line Wrapping

R carriage

Color text

Echo–e "33[40;35m ...]"

echo "Hello,world"

Echo–e "33[40;35mhell,world33[0m"

sort [Options] input file

-O Output file

-D Sort A-Z by dictionary order

-N Output 0-9 by numeric size

-R Reverse Output z-a 9-0

-k Specifies that the category is a numeric category on a field

-t field separator, split field with non-space or TAB key

MORE/ETC/PASSWD pagination Display

In the middle of the Sort–d/etc/passwd|more | is the symbol. Sort the previous processing to the back processing first. Post-page display

Sort–k3–n–r–t:/etc/passwd|more

From big to small

WC [parameters] [filename]

-C statistics Number of characters

-L Statistic Line count

-W Statistics word number space distinction

diff [Options] File/directory File/directory

Diff/etc/passwd/etc/passwd.bak

-Q only shows no differences, no detailed information is displayed

-C Displays all the text and marks the difference.

-B does not check for differences in space characters

-B Do not check blank lines

-R to compare files in subdirectories.

grep search matching supports regular expressions

Grep

-C Print only the line number count of the matching pattern

-I ignores case when matching text

-N displays its row number before each line

-V reverse output, print mismatched rows

-F file to match the list of strings in Filezhong

grep ' [tt]his ' file1.txt set case

grep ' ^[^#] ' file2.txt does not match the beginning of the line

grep "S...N" File3.txt matches any character

Sed line Edit command
s substitution

I insert

A attach

d Delete all matching rows

D Delete first-match rows

What SED can do ("line" based)

Delete

Change

Add to

Insert

Replace

Example

Sed–n ' 1,4p '/etc/passwd p is print-n does not display the original file print 1-4 lines

Sed '/80/d ' file.txt first occurrence of 80 rows to delete

Sed ' s/var/usr/g ' file.txt replaces all var with usr G to represent all

Sed ' $s/help/man/g ' file.txt replaces help from 50 lines to the last line to man before 49 no matter

Awk can work with columns, or you can work with rows, you can navigate to the first few lines, the first columns

awk [Options] ' awk script ' input file

-F FS uses FS as the field delimiter for input records = Sort–t

-f filename reads awk_script from file filename (awk script)

-V var=value set variable for Awk_script

Built-in variables for awk

/tr>

variable	feature	default /td>
FS = capital F	Enter field delimiter	space or tab /td>
,	Enter record delimiter	newline
OFS =out FS	output field delimiter	space or tab
ORS	output Record separator	break line
NF common	current record non-null field number
NR common	record number read from all Files

Example

Awk–f: ' {print nr,$1,$2} '/etc/passwd

Awk–f: ' {print nr,$1, $NF} '/etc/passwd $NF fetch last row

Awk–f: ' Nr%10==5{print nr,$0} '/etc/passwd nr= the number of rows currently processed is in addition to 10 = 5 Printing The current number of rows, outputting the entire line of output, such as 5, 15, 25 print out

Awk–f: ' nr==8,nr==13 {print nr,$0} '/etc/passwd specifies 8 rows and 13 rows.

How awk works (Tools)

$NF $NR $ A row in the first column and the second column of $

Actual test

Awk–f: ' {print $1,$3} '/etc/passwd

Awk–f: ' {print $, $NF} '/etc/passwd

Awk–f: ' {print nr,$1, $NF} '/etc/passwd NR line number

Awk–f: ' Nr==5,nr==8{print nr,$1, $NF} '/etc/passwd Specify 5-8 lines

Awk–f: ' Nr%10==5{print nr,$1, $NF} '/etc/passwd except 10

Course Sample Test

1, Grep–v "-" file.txt remove all the data with minus sign-V to show that none of the words show only-

2, wc-l file.txt display all Rows grep–v "-" file.txt |wc–l statistics all without negative numbers

3, sort–n–r–k4 file.txt |sed–n ' 1p ' sort fourth column without delimiters (that is, spaces),-n digits –r from large to small sed pipe shows the first row sed–n does not display the original file

SORT–N–R–K4 file.txt |head-1 Read First Data head first line

4. awk ' {if ($NF >3) {print $}} ' file.txt NF the last column is greater than 3 print an entire line

5. awk ' {if ($4>0,&&$4<15) {print $}} ' file.txt list fourth column greater than 0 less than 15 output whole line

awk ' {if ($4>0,&&$4<15) {print $}} ' file.txt |wc–l display number of rows

Practice:

1. grep and awk
   

   awk ' {if ($1>200801011) {[Print $}} ' file.txt
   

2,

Processing Command review:

Statistic text WC

Sorting text sort

Text/Directory comparison diff

Find key rows in a file grep/sed

Add, delete, and change sed in row text

Display the specified column in the column text awk

Calculate in column text awk

Make conditional selections in column text awk