Linux command Refresher (2)

emptying files with redirects

>the contents of filename =>filename are emptied

Command Help

$ man command

Query the description document for command commands

$ man-k keyword

Query keywords

$Info command

A more detailed description of the document

$whatis command

Brief description

$which command

The path to the binary file where command

$whereis command

All the command in the search path

Here's an example of a command (binary file). For example, man can also be used to query system functions, configuration files, and so on.

User

$Finger username

Display user username information

$ who

Show current logged in user

$ who am I

An interesting usage.

$Write username

Send message to User (end input with EOF)

$su

Become the root user

$sudo command

Execute AS Root user

$passwd

Change Password

SHELL (BASH)

$ History

Show command history under current shell

$alias

Show all commands for the nickname

$alias new_command= 'command'

Call command not New_command

$env

Show all environment variables

$Export var=Value

Set environment variable var to value

$Expr 1 + 1

Calculate the

File system

$du -sh dir

Folder size,-H human-readable units,-s only show summary

$Find . -name filename

Start with the current path and look down for the file filename

$Locate string

Find a path that contains a string

$UpdateDB

Unlike find ,Locate is not a real-time lookup. You need to update the database to get the latest information.

$Ln -s filename path

Create a soft link to the file filename in the path location

$pwd

Show current Path

$CD path

Change the current working path to Path

$CD -

Change the current path to the previous path

File

$Touch filename

If the file does not exist, create a blank file, and if the file exists, update the file read and modify times.

$RM filename

deleting files

$cp file1 file2

Copy file1 to file2

$ls -l Path

displaying file and file-related information

$mkdir dir

Create Dir folder

$mkdir -P Path

Recursively creating paths for all folders on path

$rmdir dir

To delete the dir folder,dir must be an empty folder.

$RM -R dir

Delete the dir folder and all files it contains

$rm-I. Dir

When the Dir folder is deleted, a dialog is prompt

$rm-I. Dir

Prompt once before removing more than three files, or when removing recursively. Less instrusive than-i, while still giving protection against most mistakes

$rm-F Dir

Ignore nonexistent files, never prompt

$file filename

Type description for file filename

$chown username:groupname filename

Change file ownership will be OwneR, owning group

$chmod 755 filename

Change the file's permissions to 755:owner r+w+x, Group:r+x, others:r+x

$od -c filename

displaying files in ASCII characters

File display

$Cat filename

Show Files
$Cat file1 file2

Connection display file1 and File2

$Head -1 filename

Show the first line of the file

$Tail -5 filename

Show file bottom line fifth

$diff file1 file2

Shows the difference between file1 and file2

$Sort filename

Sorts the rows in the file and displays

$Sort -f filename

When sorting, do not consider case

$Sort -u filename

sorting, and removing duplicate rows

$uniq filename

Displays the rows that are not duplicated in the file filename (same content but not adjacent rows, not duplicates)

$WC filename

The number of characters, words, and lines in the statistics file

$WC -l filename

Number of rows in the statistics file

Text

$echo string

Display string

$echo string | Cut -c5-7

5th to 7th columns of truncated text

$echo string | grep Regex

To display a row that contains a regular expression regex

$echo string | grep -o regex

Displays substrings that conform to the regular Regrex

Time and date

$Date

Current date Time

$Date + "%y-%m-%d_%t"

Display datetime in YYYY-MM-DD_HH:MM:SS format (format can refer to $man date)

$Date --date= "1999-01-03 05:30:00"

Shows the datetime from 1900-01-03 05:30:00 backwards 100 days

$Sleep 300

Sleep 300 seconds

Process

$Top

Show process information and update in real time

$PS

Shows the process under the current shell

$PS -lu username

Show the process of user username

$PS -AJX

Show all processes in a more complete format

$Kill PID

Kill PID (PID is process ID)

$Kill %job

Kill Job (Job number)

$lsof -u username

Files opened by the user username process

$DMESG

Show System Log

$ time a.out

Test the run time of the a.out

Hardware

$uname -A

Display System Information

$DF -LH

Display the usage status of all hard drives

$Mount

Show all hard disk partition mounts

$Mount partition path

Hang on partition path

$umount partition

Uninstalling partition

$sudo fdisk -L

Show All partitions

$sudo fdisk device

Create a partitioned table for device (such as/DEV/SDC). After entering, select N, p, W

$sudo mkfs -t ext3 partition

Format Partition patition(e.g./DEV/SDC1)

Modify the/etc/fstab to mount the partition automatically. Add Rows:

/DEV/SDC1 Path (mount point) ext3 defaults 0 0

$Arch

Display schema

$Cat /proc/cpuinfo

displaying CPU information

$Cat /proc/meminfo

Display memory Information

$cat/etc/issue

Show Fedora Version

$ Free

Show Memory usage

$pagesize

Display memory page size (in KByte)

Internet

$ifconfig

Displays the network interface and the corresponding IP address. Ifconfig can be used to set the network interface

$ifup eth0

Running the eth0 interface

$ifdown eth0

Close the eth0 interface

$Iwconfig

Show Wireless network interface

$Route

Displays the route table. The route can also be used to modify the routing table

$netstat

Displays the current network connection status

$Ping IP

Send ping packets to address IP

$traceroute IP

Probing the route path to address IP

$dhclient

Send DHCP requests to the DHCP host for IP addresses and other setup information.

$host domain

DNS query, look for the domain name IP corresponding to

$Host IP

Reverse DNS Query

$wget URL

Use wget to download the resources that the URL points to

$wget -M url

Image download

SSH login and file transfer

$ssh ID@host

SSH login remote server host,ID is user name.

$sftp ID@host

Login Server host,ID is user name. After the sftp login, you can use the following command to further the operation:

Get filename # download file

put filename # uploading files

LS # Lists all files for the current path on the host

CD # Change the current path on host

lls # Lists all files for the current path on the local host

LCD # Change the current path on the local host

$SCP localpath ID@host:path

Upload the file that the local LocalPath points to to the path path of the remote host

$SCP -R ID@site:path localpath

In the SSH protocol, traverse The entire file system in the download path path, to the local localpath

Compression and archiving

$zip file.zip file1 file2

Compress file1 and file2 to file.zip

$Unzip file.zip

Decompression File.zip

$gzip -c filename > file.gz

Compress file filename to file.gz

$gunzip file.gz

Unzip the file.gz . zip file

$tar -cf file.tar file1 file2

Create a tar archive

$tar -zcvf file.tar file1 file2

Create a tar archive and compress

$tar -xf File.tar

Release the TAR Archive

$tar -zxvf file.tar.gz

$tar-JXVF file.tar.bz

Unzip and release the TAR Archive