UNIX/DOS Commands that I often use…

Command	Description
sudo dscl . list /Users uid	Lists all the users ids
sudo dscl . list groups gid	Lists all the group ids
id -u id -u RakeshChouhan	Gives the UID (user id) of username RakeshChouhan — Output is 502
dig rakeshchouhan.com	Queries DNS and displays the given domain’s ip address in the terminal.
nl	Gives the number of lines the file has.
export	Used to Set Environmental variables
sudo	Execute a command as another user
sudo -i OR sudo sh	Log in as root
exit	switch back to RakeshChouhan
ssh-keygen -R localhost	Removes latest added ssh key and retains the old one.
ssh localhost	Shows the last ssh login
ssh-keygen -t rsa -P “”	Generates a SSH key (id_rsa.pub)
sudo chmod 700 /etc/ssh_host_dsa_key	Changing permissions to ssh_host_dsa_key
cat $HOME/.ssh/id_rsa.pub >> $HOME/.ssh/authorized_keys	copies the generated id_rsa.pub to authorized_keys in .ssh folder
cp	copies a file from source and pastes in the destination folder.
ln -s	Sets the link for the given fileName to the destination folder where the given filename exists
ps aux | less	Shows all current running process ids, with % of memory usage
ps	Shows all current running process ids at current instance
ps -ef	Shows all running process and as well monitor and refreshes the result in each interval
lsof	Shows all processes and PID’s
mkdir	Creates a directory for the given name.
kill 12345	Kills the process id
jps	Shows all current running Java Processes
man	Shows the manual page that you want to see
echo $JAVA_HOME	Shows the current mapped JAVA_HOME environment variable
echo $HADOOP_HOME	Shows the current mapped HADOOP_HOME environmental variable
echo $PATH	Shows the system PATH variable
clear	clears the current working terminal screen
java -version	Gives the java version
hadoop version	Gives the Hadoop Version
pwd	Shows the current working directory
exit	Ends the Terminal’s process
find -f macos	Finds the file named macos in the HardDisk
find . -type d | grep {directoryName} OR find / -name {directoryName} -type d	Finds the directory named {directoryName} in the HardDisk
rm -R -i	Removes/Deletes each file and each sub directory from the given directory Name with a prompt for each file and sub directory
rm -rf	Removes/Deletes all files and sub directories without a prompt.
rmdir	Deletes the given directory
ls	Lists out the Non hidden files and directories in the current folder
ls -a	Lists out all the hidden and non hidden files and directories in the current folder
ls -l	Lists out all non hidden files and folders alphabetically, and shows the file and directory permissions,user,created date.
ls -help	Lists out all the non hidden files and folders with more details (Users, Groups, Access levels)
ls -l file.txt; echo $?	Check if the file.txt is present or not in a particular directory.
wc	Displays the Counts of lines, words, bytes in this order for the given fileName
cd	Change Directory
cd ~	Go to previous directory
du -sh | grep G	Determines the Disk Usage in GB.
tar -xvfz	Un-tars filename
vi	Opens file with vi editor tool.
jar -cvf WAR_NAME.war *	Creates a war for the given folder (Note that you should be in that folder for that folder to be war)
grep ‘{WORD_TO_FIND}’ ‘{IN_FILE}’	Searches a text in the file. Ex: grep boo /etc/passwd. See grep for more options.
grep {GREP_OPTIONS} ‘{WORD_TO_FIND}’ ‘{IN_FILE}’	Searches a text in the file. If using grep option a). -A 10 Displays 10 more lines after (from the line where the text was found). Ex: grep -A 10 boo /etc/passwd. b). -B 10 Displays 10 more lines before (from the line where the text was found). Ex: grep -B 10 boo /etc/passwd. c). -C 10 Displays 10 more lines before and after (from the line where the text was found). Ex: grep -C 10 boo /etc/passwd. See grep for more options.
what is	Gives What is What. What Does What ????
touch	Creates a text file
cat > {fileName}	Creates a fileName and opens it for edit/writing. “control + z” saves the file and returns.
mv	Moves a file from Source location and drops in destination location
rmr	Removes the mentioned file from the destination location
ifconfig	Gives the ip, mac addresses
netstat	Gives the network status
netstat – a | grep “10123”	Determines which remote hosts are connecting to your host on a particular port say 10123
nslookup	Determines your hostname and IP and viceversa
uptime	Determines from how many days your server is up
stat	Displays the fileName attributes/properties
sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist	Loads FTP Server
sudo -s launchctl unload -w /System/Library/LaunchDaemons/ftp.plist	UnLoads FTP Server
sudo apachectl start	Starts MacOSX default Apache Server
sudo apachectl stop	Stops MacOSX default Apache Server
sudo apachectl restart	ReStarts MacOSX default Apache Server
httpd -v	Gives the current Apache version
head -5 test.txt	Prints/Displays the first 5 lines of file test.txt
sed ‘5,$d’ test.txt	Prints/Displays the first 4 lines of file test.txt — sed is the text editor same as vi editor.
tail -5 test.txt	Prints/Displays the last 5 lines of file test.txt
sed -n ‘$p’ test.txt	Prints/Displays the last 4 lines of file test.txt — sed is the text editor same as vi editor.
head -5 test.txt | tail -1	Displays/Prints the 5th line from file test.txt
sed -n ‘4 p’ test	Displays/Prints the 5th line from file test.txt using sed editor
grep -c “Unix”	Counts the number of times the word ‘Unix’ occurs in the given file
sed s/Unix/UNIX/g	Replaces the word containing ‘Unix’ with ‘UNIX for the given filename
cut -f3	Gives only phone numbers, if my filename has tab separated Name, Address and Phone numbers.
awk -f3	Gives only phone numbers, if my filename has tab separated Name, Address and Phone numbers.
exit -1	Logout and Fail a Shell Script programatically.
chown	Change file owner to the given userName of a given filePath
chgrp	Change file groupName for the given fileName
sudo chattr +i/-i	Change advanced file attributes.
/usr/sbin/system_profiler SPHardwareDataType | grep Memory	Shows RAM memory (16GB)
df -h	Determines how much space is left in current drive. Determines Configured SWAP space. Swap files are created in (/private/var/vm) directory.
uname -p or arch	Displays the processor type. (Current Processor architecture type is i386)
uname -a	Displays the type of OS running on top of UNIX. (Here Darwin)
sw_vers	Shows the Operating Systems version.
gcc -v	Determines whether the required version of gcc is installed
ping or telnet	Determines if a remote host is alive or not
top	Determines which process is taking how much CPU
telnet hostname port	Check if a particular process is listening on a particular port on remote host.
sudo scutil –set HostName rakeshchouhan.com	Sets the hostname (HostName is case sensitive)
hostname	Gives you the hostname (case-sensitive). This is the same command in Windows. Also, you can “echo %COMPUTER_NAME%” in Windows to get the hostname.
sudo lsof -i -P | grep 8001	gives the process id of the application which is using port 8001 (PID is 3rd from the left)
unzip -t file.zip	Determines if a Zip file is corrupted.
unzip -j file.zip	Unzips a Zip file.
echo “unix” | rev	Reverses a string. From unix to xinu
echo “C for Cat” | rev | cut -f1 -d’ ‘ | rev	Gets the last word from a line in Unix file. Explanation: The entire line is reversed (taC rof C), then we cut the first word, we get (taC) and reverse it again.
sysctl -n machdep.cpu.brand_string	Gives Processor information ex: Intel(R) Core(TM) i7-3820QM CPU @ 2.70GHz
system_profiler	Gives all the information related to PC (Camera, Bluetooth, Processor, Memory, Wireless, etc..)
sytem_profiler SPHardwareDataType	Gives Hardware Overview Informations.
sysctl -a | grep machdep.cpu	Gives all CPU related information
find / -name .DS_Store -delete	This deletes all .DS_Store files from all folders of MAC OSX file system.
curl -O http://www.interior-dsgn.com/apache/maven/maven-3/3.1.1/source/apache-maven-3.1.1-src.tar.gz	Downloads apache-maven-3.1.1-src.tar.gz
sudo ln -s /Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk /System/Library/Java/JavaVirtualMachines/1.6.0.jdk	Set a different Java Virtual Machine
sudo apachectl start	Starts apache2 server (verify http://localhost)
sudo apachectl stop	Stops apache2 server
brew update	Use brew to install packages. This command updates brew formulae’s
brew install {packageName}	Installs brew packages. Ex: brew install apache-spark
watch -n1 ls	Watches the folder every one second. This is useful to keep a continuous watch on any folder, instead of typing ls -l on the folder every time. In order to watch for every 5 seconds for a given folder, use “watch -n5 ls” Note that ‘watch’ command isn’t available implicitly. So we need to brew it before. Ex: brew install watch
nc -l 8081	NetCat tool to allows clients to read from or write to network connections using certain protocols. In this case the client will be listening to port 8081. Note: -l stands for listen
nc 127.0.0.1 8081	NetCat tool to allows clients to read from or write to network connections using certain protocols. In this case the client will be writing to 127.0.0.1 host at port 8081.