# Basic Linux commands - mkdir – make directories Usage: mkdir [OPTION] DIRECTORY… eg. mkdir lhn - ls – list directory contents Usage: ls [OPTION]… [FILE]… eg. ls, ls ­l, ls lhn - cd – changes directories Usage: cd [DIRECTORY] eg. cd lhn - pwd ­- print name of current working directory Usage: pwd - vim – Vi Improved, a programmers text editor Usage: vim [OPTION] [file]… eg. vim lhn.txt - cp – copy files and directories Usage: cp [OPTION]… SOURCE DEST eg. cp sample.txt sample_copy.txt cp sample_copy.txt target_dir - mv – move (rename) files Usage: mv [OPTION]… SOURCE DEST eg. mv source.txt target_dir mv old.txt new.txt - rm ­ remove files or directories Usage: rm [OPTION]… FILE… eg. rm file1.txt , rm ­rf some_dir - cat – concatenate files and print on the standard output Usage: cat [OPTION] [FILE]… eg. cat file1.txt file2.txt cat ­n file1.txt - grep ­- print lines matching a pattern Usage: grep [OPTION] PATTERN [FILE]… eg. grep ­i apple sample.txt wc ­- print the number of newlines, words, and bytes in files Usage: wc [OPTION]… [FILE]… eg. wc file1.txt - wc ­L file1.txt sort – sort lines of text files Usage: sort [OPTION]… [FILE]… eg. sort file1.txt sort ­r file1.txt - vim – Vi Improved, a programmers text editor Usage: vim [OPTION] [file]… eg. vi hello.c # oops concepts https://www.javatpoint.com/java-oops-concepts http://www.idc-online.com/technical_references/pdfs/information_technology/Object_Oriented_Programming_Oop_Concepts_With_Examples.pdf -- direct pdf # sql commands https://www.javatpoint.com/dbms-sql-command https://www.codecademy.com/articles/sql-commands -- direct commands https://www.hcoe.edu.np/uploads/attachments/r96oytechsacgzi4.pdf -- direct commands sql in turorial point