Command Line Linux

File Commands
Code:

ls # Directory listing
ls -al # Formatted listing with hidden files
ls -lt # Sorting the Formatted listing by time modification
cd dir # Change directory to dir
cd # Change to home directory
pwd # Show current working directory
mkdir dir # Creating a directory dir


cat >file # Places the standard input into the file
more file # Output the contents of the file
head file # Output the first 10 lines of the file
tail file # Output the last 10 lines of the file
tail -f file # Output the contents of file as it grows,starting with the last 10 lines
touch file # Create or update file
rm file # Deleting the file
rm -r dir # Deleting the directory
rm -f file # Force to remove the file
rm -rf dir # Force to remove the directory dir
cp file1 file2 # Copy the contents of file1 to file2
cp -r dir1 dir2 # Copy dir1 to dir2;create dir2 if not present
mv file1 file2 # Rename or move file1 to file2,if file2 is an existing directory
ln -s file link # Create symbolic link link to file

Process management

Code:

ps # To display the currently working processes
top # Display all running process
kill pid # Kill the process with given pid
killall proc # Kill all the process named proc
pkill pattern # Will kill all processes matching the pattern
bg # List stopped or background jobs,resume a stopped job in the background
fg # Brings the most recent job to foreground
fg n # Brings job n to the foreground

File permission
Code:

chmod octal file # Change the permission of file to octal,which can be found separately for user,group,world by adding,

  1. 4-read(r)
  2. 2-write(w)
  3. 1-execute(x)

Searching
Code:

grep pattern file # Search for pattern in file
grep -r pattern dir # Search recursively for pattern in dir
command | grep # Search pattern in the output of a command pattern
locate file # Find all instances of file
find . -name filename # Searches in the current directory (represented by a period) and below it, for files and directories with names starting with filename
pgrep pattern # Searches for all the named processes , that matches with the pattern and, by default, returns their ID

System Info
Code:

date # Show the current date and time
cal # Show this month’s calender
uptime # Show current uptime
w # Display who is on line
whoami # Who you are logged in as
finger user # Display information about user
uname -a # Show kernel information
cat /proc/cpuinfo # Cpu information
cat proc/meminfo # Memory information
man command # Show the manual for command
df # Show the disk usage
du # Show directory space usage
free # Show memory and swap usage
whereis app # Show possible locations of app
which app # Show which applications will be run by default

Compression
Code:

tar cf file.tar file # Create tar named file.tar containing file
tar xf file.tar # Extract the files from file.tar
tar czf file.tar.gz files # Create a tar with Gzip compression
tar xzf file.tar.gz # Extract a tar using Gzip
tar cjf file.tar.bz2 # Create tar with Bzip2 compression
tar xjf file.tar.bz2 # Extract a tar using Bzip2
gzip file # Compresses file and renames it to file.gz
gzip -d file.gz # Decompresses file.gz back to file

Network
Code:

ping host # Ping host and output results
whois domain # Get whois information for domains
dig domain # Get DNS information for domain
dig -x host # Reverse lookup host
wget file # Download file
wget -c file # Continue a stopped download

Shortcuts
Code:

ctrl+c # Halts the current command
ctrl+z # Stops the current command, resume with fg in the foreground or bg in the background
ctrl+d # Logout the current session, similar to exit
ctrl+w # Erases one word in the current line
ctrl+u # Erases the whole line
ctrl+r # Type to bring up a recent command
!! # Repeats the last command
exit # Logout the current session

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