✨ Linux-Training-Sessions ✨

⚛️ Day 1 Commands :

• cal : Prints an ASCII calendar of the given month or year.
• date : Displays the current date and time.
• echo : Displays lines of text or string which are passed as arguments on the command line.
• clear : Brings the command line on top of the computer terminal.
• script : Makes typescript or records all the terminal activities.
• ls : Lists directory contents of files and directories.
• who : Prints information about users who are currently logged in.
• whoami : Allows Linux users to see the currently logged-in user.
• tty : Any terminal on Linux/Unix systems.
• uname & uname -r : displays the information about the system. Option -r displays the Linux kernel release info.
• cd (change directory) : Used to move efficiently from the current working directory to different directories in our System.
• mkdir : Creates multiple directories in the current location.
• rmdir : Removes the directory, specified by the Directory parameter, from the system.
• rm -r : It will recursively delete a directory and all its contents.

⚛️ Day 2 Commands :

• man : Used to display the user manual of any command that we can run on the terminal.
• ls options :
  • ls -l : Displays the contents of the current directory in a long listing format, one per line (show permissions).
  • ls -a : Lists all files including hidden files (files with names beginning with a dot).
  • ls -author : Lists the contents in the specified directory along with its owner.
  • ls -C : Lists entries by columns.
  • ls -d : Lists directories - with ' */'.
  • ls -r : It is used to print the list in reverse order.
• file creation through cat command :
  • cat > (to overwrite)
  • cat >> (to append)
  • cat (to view)
• Empty file creation using touch command.
• cp : cp stands for a copy. This command is used to copy files or groups of files or directories.
• mv : Moves files and directories from one directory to another or renames a file or directory.
• file : Used to determine the type of a file.
• wc command : (stands for word count)
  • wc -l : Prints the number of lines in a file.
  • wc -w : Prints the number of words in a file.
  • wc -c : Displays the count of bytes in a file.
  • wc -m : Prints the count of characters from a file.
  • wc -L : Prints only the length of the longest line in a file.
• cmp : Used to compare two files byte by byte and helps to find out whether the two files are identical or not.
• comm : Compares two sorted files line by line and writes to standard output; the lines that are common and the lines that are unique.
• sort : Prints the lines of its input or concatenation of all files listed in its argument list in sorted order.
• redirection operator >
• rm -i for interactive deletion of any file.
• character class :
  • ????? placeholders
  • asterisks(**) to denote all

⚛️ Day 3 Commands :

• chmod (change mode) :
  • relative permission : ('+' symbol is used add and '-' symbol is used to remove a specific permission from user , group or others.)
    • using ±r or ±w or ±x with ugo or a. ( 'a' stands for all , i.e., 'u'(user), 'g'(group) & 'o'(others). )
    • using ugo/a = ±r or ±w or ±x.
  • absolute permission using numbers :
    • 4 : read (r--)
    • 2 : write (-w-)
    • 1 : execute (--x)
      • 3 (2+1) : write & execute (-wx)
      • 5 (4+1) : read & execute (r-x)
      • 6 (4+2) : read & write (rw-)
      • 7 (4+2+1) : read, write & execute (rwx)
• chmod -R : To assign same permissions of root directory to sub-directories.
• umask : The umask command sets the file-creation mask using this format:
  • where mask is an octal number or symbolic value that correspond to the permissions to be disabled.
  • This umask command adds write permission to the group:
    • With no arguments, umask displays the current value.
• ls -ls
• redirection of output using > and >>
• Character class :
  • [0-9] for digits (same as [!a-z]).
  • [a-z] for chars (same as [!0-9]).

⚛️ Day 4 Commands :

• Linux- Vi Editor (it has three modes of operation) :
  • Command mode : Operations such as cut, copy, paste, delete, undo, redo etc.
  • Insert mode : Type in new text.
  • Esc mode : Extended commands for saving, exiting, search-and-replace can executed here.
• vi to open a file.
• Input Mode Commands :
  • i : Insert text to left of the cursor(Existing text shifted right).
  • a : Append text to right of cursor(Existing text shifted right).
  • I : Insert text at the beginning of line.
  • A : Append text at the end of the line.
  • o : Open line below.
  • O : Open line above
  • rch : Replaces single character under cursor with ch.
  • R : Replaces text from cursor to right.
  • s : Replaces single character under cursor with any number of characters.
  • S : Replaces entire line.

⚛️ Day 5 Commands :

• grep command in pattern matching :
  • grep -v : Selects the non-matching lines of the provided input pattern.
  • grep -e : Union two grep patterns.
  • grep -n : Prefix each line of the matching output with the line number in the input file.
  • grep -c : Count number of lines matching to given pattern.
  • grep -i : Ignores case distinctions in patterns and input data.
  • grep "^pattern" (find specified pattern at the beginning).
  • grep "pattern$" (find specified pattern at the end).
  • grep "pattern1" |grep "pattern2" (pipe operator redirection used).

⚛️ Day 6 Commands :

• /dev/null (special file of linux that has size of 0 bytes it's works like insularator)

• /dev/tty (represent the own terminal)

• | (pipe command)

• ( ls | wc -l who |wc -l )

• tee

• ls |tee file

• Command Substitution {`}

• echo "Number of files are {`ls |wc -l } in present directorty"

• Shell Variables

• $x

• expr $x + $y

• expr $x - $y

• expr $x * $y

• expr $x / $y

• exit status of last command echo $? ( 0 -- for successful 1 -- for i=unsuccessful )

• x=20;y=30;z=40;m=20

• test $x -eq $y;echo $? (equals)

• test $x -ne $y;echo $? (not equals)

• test $x -gt $y;echo $? (greater than)

• test $x -lt $y;echo $? (less than)

• test $x -ge $y;echo $? (greater than or equals to)

• test $x -le $y;echo $? (less than or equals to)

• who|tee /dev/tty|wc -l

• ls |tee /dev/tty|grep -l "poem" *|wc -l >count

• cat file>file (earse all the content of file)

⚛️ Day 7 Commands :

⚛️ Day 8 Commands :

• process command ps
• ps - l
• ps -f (full screen )
• ps -e (all process )
• kill process_id
• kill -9 process_id (super kill)
• & (at the end of command to make it background process)
• process scheduling
• at (for one time scheduling)
• batch
• crontab