Most commonly used Unix command

Process using port 

lsof -i:80

File operation

Insert new line: esc i enter

Delete letter: esc x

Delete Line: esc d

sudo vi file name

Editor: gedit filename

find . -name *.txt| grep -i keyword

ls -l

viewing elnf of files

vi fileName -->Shift g

http://www.tecmint.com/35-practical-examples-of-linux-find-command/

switching to root user: sudo su

Removing file recursively: rm abc.* -r

space available:

(disk free)

df -m

df -g

df -h  // human readable

df   m/g (megabytes/gigabytes)

df -ah // all files

memory: 

free -h

free -h -t

free -m / in MB

free -g / in GB
Process

list out process running:ps -ef

Find Java process: ps –ef | grep java

Find tomcat process: ps- ef | grep cataline

Kill Process: kill -9 processid

Linking
Creating link of an existing file
ln -s filexisting filenew
changing owner group
chown user_name:group_name file_name.

File Download
GNU Wget is a free utility for non-interactive download of files from the Web. It supports HTTP, HTTPS, and FTP protocols, as well as retrieval through HTTP proxies.
download jdk
wget http://download.oracle.com/otn-pub/java/jdk/6u31-b04/jdk-6u31-linux-x64-rpm.bin
 ftp archive requires the --passive-ftp flag on wget.
   wget --passive-ftp http://www.ccrnp.ncifcrf.gov/~toms/ftp/ev.p

Installation
#rpm-  rpm is packaging technique followed by few linux os.
#yum - an utility which updates and install packagesand their dependencies using internate.
yum package name.
yum >savefile  output of a command in a file

Install  Apache: yum install httpd
Install JDK:  yum install jdk
  ./jdk-6u32-linux-x64-rpm.bin
version check:
which java

Creating Tar/Compressing and uncompressing tar files
#To combine multiple files and/or directories into a single file, use the following command:
tar -cvf file.tar inputfile1 inputfile2
#Replace inputfile1 and inputfile2 with the files and/or directories you want to combin
#To separate an archive created by tar into separate files, at the shell prompt, enter:
tar -xvf file.tar
#f  option, tar assumes you really do want to create a tape archive instead of joining up a number of files. The  v  option tells tar to be verbose, which reports all files as they are added.
 Compressing and uncompressing tar files
 tar -cvzf file.tar.gz inputfile1 inputfile2
# z  option tells tar to zip the archive as it is created. To unzip such a zipped tar file, enter:

tar -xvzf file.tar.gzTar everything in the current directory but exclude two files

tar cvpf mytar.tar * --exclude=index.html --exclude=myimage.png

#To separate a tar archive that was compressed by gzip, enter:
gunzip -c file.tar.gz | tar -xvf -

#Extract jar file

jar xf xyz.jar

Make a Tar file" : tar -czf folder_name.tar.gz folder_name

Compress a single file: gzip file_name.txt -> file_name.txt.gz

Searching

Searching some keyword in a file
grep -n keyword  localhost_tomcat.log
-n shows line number 

egrep:
egrep stands for extended grep and it is more powerful than grep command in Unix and allows more regular exception like you can use "|" option to search for either Error or Exception by executing just one command.

egrep 'Error|Exception' logfile.txt

Show only n lines from the search result

shows only 400 lines from line -572458

grep -n keyword localhost_tomcat.log head -572458 catalina.out | tail 400

grep -r catalina.xml .

tail -100f localhost_latest.log

 find . -name *file_name* -type f

find <directory_location> -name "*file_name*" | grep "key_word_from_output"
eg. directory_location: . , /, ../

Others:

history

echo $CATALINA_HOME

sudo -i :acquires the root user's environment.

history | grep process_name 

starting apache server

sudo httpd -k start

Setting Environment variable:

export JAVA_HOME=/usr/lib/jvm/java-6-sun

Setting environment variable permanently 

vi ~/.bash_profile 

 export ABC=XYZ
print all environment variable : printenv 

Switch to a different user

su -l <user_name>

Getting IP configuration

ipconfig//win

ifconfig// mac

Querying DNS to get IP address mapping

nslookup google.com

network statistics

netstat -n

TCP packet dump

tcpdump -l -x

tcpdump allows us to save the packets that are captured, so that we can use it for future analysis. The saved file can be viewed by the same tcpdump command.

Reload environment variable
 . /Users/<user_id>/.bash_profile 

Sftp:

Download

 sftp user@host_name:src_path/file_name dlocal_dest_path
grep:
Show 5 more lines along with the keyword line

grep 'some_key_word'  application.log  -A5

5 lines before

grep 'some_key_word'  application.log  -B5

in between 5 lines

grep 'some_key_word'  application.log  -C5

error count

grep 'some_key_word'  application.log  | wc -l

Running Shell Script:

& -> Running script in background.

Stop running ctrl z

continue runnning in background: bg, foreground: fg

foreground : z

Disk usage:

du -h  -d1

awk: 

data extraction utility (Aho, Weinberger and Kernighan )

awk ' /'pattern'/ {print $2} '

ls -l | awk '{print $3}'

kill running program foo

 kill -9 $(ps -ef | grep java | awk '{print $2}')

awk ’{ print $1 > "names.unsorted"

       command = "sort -r > names.sorted"

       print $1 | command }’ inputfile

       https://linuxconfig.org/learning-linux-commands-awk

#Cron expression

crontab -e //edit

cromtab -i // info