Linux Basic Commands

## 1. User Environment

Details	commands	Remarks
loggedInUser	whoami
Current User	id
Current directory	Pwd
List of files \directories	ls ls -lr ls -ltr

Details	commands	Remarks
System login processes	who -l who -l -H
Count all login names and number of users logged on	who -q -H who -H
Display the current run level	who -r
Display system boot level	who -b	who -b -r
Display all information	who -a	-a : Same as -b -d –login -p -r -t -T -u -b Time of last system boot -d Print dead processes -H Print line of column headings -l Print system login processes -m Only hostname and user associated with stdin -p Print active processes spawned by init -q All login names and number of users logged on -r Print current runlevel -t Print last system clock change -T Add user’s message status as +, – or ? -u List users logged in

## 2. File Management:

Details	Commands	Remarks
Create directory	mkdir testdir
Copy files	cp ./dir/ ./dir2/	cp file.doc newfile.doc cp main.cs demo.html lib.vb backup cp main.c demo.h lib.c /home/project/backup/ #Preserve file attributes cp -p filename /path/to/new/location/myfile #Copy all files in backup folder cp * /home//backup #Copy all doc files in backup folder cp *.doc /home/backup #Copy all files recursively in backup folder cp -R * /home/backup #Copy file command with interactive option cp -i foo bar # Verbose output with cp command cp -v file1 file2 -r - recursive -v - verbose
Copy files & directories recursively	cp ./dir/ ./dir2/ -r	-r - recursive -v - verbose
Move files	mv ./file1 ./dir1/	-r - recursive -v - verbose
Rename files	mv ./file1 ./file2	-r - recursive -v - verbose
Move files from one directory to other directory	mv ./dir1 ./dir2	-r - recursive -v - verbose
Delete files	rm ./filename rm ./filename1 ./filename2 ./filename3 rm *.pdf	-r - recursive -v - verbose
Delete directories	rmdir ./dirName/	-r - recursive -v - verbose -i confirmation
To view content of file	cat filename	cat file cat /path/file
To create a file called “test.txt”	cat > test.txt	##Type following test files and press Ctrl+D at the end of the file This is a line1 in test file. This is a line2 in file. ## press control-D cat test.txt
To view big files using shell filters (more, less)	cat dwh-log.log | more cat dwh-log.log | less	more dwh-log.log less dwh-log.log
To combine two or more files	cat test1.txt test2.txt > test-log.txt cat test-log.txt
To view file with line numbers	cat -n test1.txt cat -number test1.txt
To display TAB characters as ^I	cat -T test.txt
To display $ at end of each line,	cat -E test.txt cat --show-ends test.txt
Use ^ and M- notation, except for LFD and TAB and show all nonprinting	cat -v test.txt cat --show-nonprinting testfile.txt
To show all	cat -A test.txt cat --vET test.txt
View all files in directory	cat * cat *.cs
joining binary files	cat file1.bin file2.bin file3.bin > large.tar.gz ### extract it tar -zxvf large.tar.gz
To show all	cat -A test.txt cat --vET test.txt

###  2.1 finding lines using cat , sed and awk commands:

Details	Commands	Remarks
Read last 100 lines of the file	cat {filename} | tail -100 tail -100f {filename}	Example: cat hugfile.txt| tail -100 tail -100f hugfile.txt
Read first 100 lines of the file	cat {filename} | head -100 head -100f {filename}	Example: cat hugfile.txt | head -100 head -100f hugfile.txt
Print \Read nth line of the file using SED (stream editor)	cat {filename} | awk 'NR=={n}'	Example: cat hugefile.txt | awk 'NR==25'
Print \Read nth line of the file using awk	cat {filename} | sed -n '{n}p' sed -n '{n}p' < {filename}	Example: cat hugfile.txt | sed -n '100p' sed -n '100p' < hugfile.txt
Print \Read from mth line to nth lines of the file using SED (stream editor)	cat {filename} | sed -n '{n},{m}p' sed -n '{n},{m}p' < {filename}	Example: cat hugfile.txt | sed -n '10,50p' sed -n '10,55p' < hugfile.txt
Print \Read from mth line and nth lines of the file using SED (stream editor)	cat {filename} | sed -n '{m}p;{n}p' sed -n '{m}p;{n}p' < {filename}	Example: cat hugfile.txt | sed -n '10p;40p' sed -n '10p;40p' < hugfile.txt

###  2.2 Replace words file using sed (stream editor) command:

Details	Commands	Remarks
Replacing or substituting string: Sed command is mostly used to replace the text in a file.	sed 's/{word}/{replacewith}/' {filename}	Example: The below simple sed command replaces the word “data” with “DWH” in the file. sed 's/data/DWH/' hugefile.txt
Replacing or substituting string: Sed command is mostly used to replace the text in a file.	sed 's/{word}/{replacewith}/' {filename}	Example: The below simple sed command replaces the word “data” with “DWH” in the file. sed 's/data/DWH/' hugefile.txt
Replacing the nth occurrence of a pattern in a line: Use the /1, /2 etc flags to replace the first, second occurrence of a pattern in a line.:	sed 's/{word}/{replacewith}/{n}' {filename}	Example: The below simple sed command replaces the word “data” with “DWH” in the file for 2nd occurance. sed 's/data/DWH/2' hugefile.txt
Replacing all the occurrence of the pattern in a line : The substitute flag /g (global replacement) specifies the sed command to replace all the occurrences of the string in the line.	sed 's/{word}/{replacewith}/g' {filename}	Example: The below simple sed command replaces the word “data” with “DWH” in the file fora all occurance. sed 's/data/DWH/g' hugefile.txt
Replacing from nth occurrence to all occurrences in a line : The substitute flag /{n}g (global replacement) specifies the sed command to replace all the occurrences of the string in the line.	sed 's/{word}/{replacewith}/{n}g' {filename}	Example: The below simple sed command replaces the word “data” with “DWH” in the file for all occurance from nth occurance. sed 's/data/DWH/5g' hugefile.txt
Replacing from nth occurrence to all occurrences in a line : The substitute flag /{n}g (global replacement) specifies the sed command to replace all the occurrences of the string in the line.	sed 's/{word}/{replacewith}/{n}g' {filename}	Example: The below simple sed command replaces the word “data” with “DWH” in the file for all occurance from nth occurance. sed 's/data/DWH/5g' hugefile.txt
Parenthesize first character of each word : This sed example prints the first character of every word in parenthesis.	echo "{Tex}" | sed 's/\(\b[A-Z]\)/\(\1\)/g'	Example: echo "Welcome To The Geek Stuff" | sed 's/\(\b[A-Z]\)/\(\1\)/g'
Replacing string on a specific line number: restrict the sed command to replace the string on a specific line number.	sed '{n} s/{data}/{ReplaceWith}/' {File}	Example: sed '3 s/data/SWH/' hugefile.txt
Duplicating the replaced line with /p flag: The /p print flag prints the replaced line twice on the terminal. If a line does not have the search pattern and is not replaced, then the /p prints that line only once.	sed 's/{data}/{ReplaceWith}/p' {File.txt}	Example: sed 's/data/SWH/p' hugefile.txt
Replacing string on a range of lines: can specify a range of line numbers to the sed command for replacing a string.	sed '1,3 s/{data}/{ReplaceWith}' {file}	Example: sed '1,3 s/data/DWH' hugefile.txt

###  2.3 Deleting lines from a particular file  using sed (stream editor) command:



#### 2.3.1 To Delete a particular line say n in this example

```sh 
# Syntax:
sed 'nd' {filename}

# Example:
sed '5d' hugefile.txt
```

#### 2.3.2 To Delete a last line
```sh 
# Syntax:
sed '$d' {filename}

#Example:
sed '$d' hugefile.txt
```

#### 2.3.3  To Delete line from range x to y

```sh
#Syntax:
 sed 'x,yd' {filename}

#Example:
sed '3,6d' hugefile.txt
```

#### 2.3.4 To Delete from nth to last line

```sh
#Syntax:
sed 'nth,$d' {filename}

#Example:
sed '12,$d' hugefile.txt
```

#### 2.3.5. To Delete pattern matching line

```sh
#Syntax:

sed '/pattern/d' {filename}

#Example:
sed '/data/d' hugefile.txt
```

###  2.3 File Management-vi Editor with Commands:


* The vi editor is elaborated as visual editor. It is installed in every Unix system.

The vi editor has two modes:

**Command Mode**:
					In command mode, actions are taken on the file. The vi editor starts in command mode.To enter text, you have to be in insert mode, just type `i`

                    
**Insert Mode**: In insert mode, entered text will be inserted into the file. The Esc key will take you to the command mode from insert mode.

By default, the vi editor starts in Command mode.



**To save and quit**:
  save and quit vi editor from command mode.
 Before writing save or quit command you have to press colon (:). Colon allows you to give instructions to vi.

exit vi Commands:
------------------

|Commands|	Action|Remarks|
| :---         |     :---:      |          ---: |
|:wq	|Save and quit| |
|:w	|Save| |
|:q	|Quit| |
|:w fname	|Save as fname | |
|ZZ	 || Save and quit| |
|:q!	| Quit discarding changes made | |
|:w! |Save (and write to non-writable file) ||

### 2.4 File Management-list files \directories:

Details	commands
List all directories in Unix	ls -l | grep '^d'
list directories for the current directory	ls -d */ find . -maxdepth 1 -type d
List of directories for given directory	ls -d /etc/*/ | more
List only files in current directory:	ls -l | grep -v '^d'
List all directories in a directory recursively	find . -type d -ls |more find /etc/ -type d -ls
List all files in a directory recursively	find . -type f -ls find /etc/ -type f -ls | more
Put above two aliases in your bash shell startup file:>	$ cd $ vi .bash_profile Append two lines: You can create two aliases as follows to list only directories and files. alias lf="ls -l | egrep -v '^d'" alias ldir='ls -d */' #alias ldir="ls -l | egrep '^d'"
text in files	find . -exec grep -rl "<searchText>" {} \; examples: find . -exec grep -rl "user" {} \;

###2.5 File Management-How to copy \move files between two unix \linux servers using scp

```sh 
scp [options] username1@source_host:directory1/filename1 \
			  username2@destination_host:directory2/filename2

```
**Details**
* The location of the source file is specified by username1@source_host:directory1/filename1, which includes the:
* Name of the account on the host computer (username1)
* Hostname of the computer on which the source file resides (source_host)
* Name of the directory containing the source file (directory1)
* Filename of the source file (filename1)
* The location to which the source file will be copied is specified by username2@destination_host:directory2/filename2, which includes the:
* Name of the account on the destination computer (username2)
* Hostname of the computer to which the source file will be copied (destination_host)
* Name of the directory to which the source file will be copied (directory2)
* Filename of the copy (filename2)


**Examples**: 

```sh 
  scp ~/sample.txt raz@dev1.aztd.com:~/testdir
  
# It will copy sample.txt from current connected server to testdir folder in dev1 server/
```

```sh 
  scp  -r  raz@dev1.aztd.com:~/dev1-test  ~/testdir
  
# it will copy all files in  dev1-test  directory from dev1 server to testdir directory in connected server recursively.
```

```sh 
  scp  -  raz@dev1.aztd.com:"~/dev1-test/*.txt  ~/testdir
  
# it will copy all text files in  dev1-test directory from dev1 server to testdir directory in connected server.
```

```sh 
  scp   raz@dev1.aztd.com:~/dev1-test/*.pdf  raz@dev2.aztd.com:~/dev2-test ~/testdir
  
# it will copy all pdf files in dev1-test directory from dev1 server to testdir directory in dev2 server.
```

###2.6  File Management- Archiving -Z commands

  
Details
 	commands	
 
 	Remarks	
 
  
Uncompressing or UnPacking files
 gzip -d test.ods.gz	 
 
 Display content after uncompress file 
 cat test.ods |less 	 
  
  
Display the contents of a compressed file
zless data.ods.gz 
zmore data.ods.gz 
 
 
 
  
Concatenate compressed files with out using gzip & cat
 zcat TestReadme.gz 
 
 
  
  
Compare compressed files.
 zdiff file1.gz file2.gz  
zcmp test1.gz test2.gz 
 
 
  
  
Search word in Compressed files
 zegrep -w '^Test1|Test2' Test.gz
  
 zgrep 'wordToSearch' Test.gz
 

  	zgrep 'Test' /path/to/log/file.gz 
 
	zgrep 'mail' /var/log/maillog-*.gz 

	zgrep 'error' /var/log/error.log*.gz  

    zgrep --color 'Failed login for' /var/log/secure*
  
  
  
Search files in a ZIP archive for lines matching a pattern:
 zipgrep *.cs Project.zip 
 
 
  
  
Search files in a ZIP archive for lines matching a pattern:
 zipgrep *.cs Project.zip 
 
 
  
  

## 3.Networking


### 3.1 Networking-How to check connectivity of another server server 


```sh 
 ping <ipAddress>
 ping <hostName>
 
 ping <FQDNForHostname>

Example:

	ping 172.24.541.100

	ping aztd1.azure.com
 
```

###3.2 Networking-How to check connectivity of another server server over particular port using ssh

```sh 
 ssh -p <portNumer> -v <ipAddress>
 
 ssh -p <portNumer> -v <hostName>
 
 ssh -p <portNumer> -v  <FQDNForHostname>

Example:

	ssh -p 9050 172.24.541.100

	ssh -p 9040  aztd1.azure.com
 
```