1. LINUX COMMANDS INTRODUCTION TO LINUX: Linux is a Unix-like operating system that was designed to provide personal computer users a free or very low-cost operating system comparable to traditional and usually more expensive Unix systems. Linux has a reputation as a very efficient and fast-performing system. Linux's kernel (the central part of the operating system) was developed by Linus Torvalds at the University of Helsinki in Finland. To complete the operating system, Torvalds and other team members made use of system components developed by members of the Free Software Foundation for the GNU Project. BASIC LINUX COMMANDS 1.bc COMMAND: bc command is used for command line calculator. It is similar to basic calculator. By using which we can do basic mathematical calculations. SYNTAX: The Syntax is bc [options]

2. 2.cal COMMAND: cal command is used to display the calendar. SYNTAX: The Syntax is cal [options] [month] [year] 3.clear COMMAND: This command clears the terminal screen. SYNTAX: The Syntax is Clear 4.cd COMMAND: cd command is used to change the directory. SYNTAX: The Syntax is cd [directory | ~ | ./ | ../ | - ]

3. 5.cp COMMAND: cp command copy files from one location to another. If the destination is an existing file, then the file is overwritten; if the destination is an existing directory, the file is copied into the directory (the directory is not overwritten). SYNTAX: The Syntax is cp [OPTIONS]... SOURCE DEST 6.date COMMAND: date command prints the date and time. SYNTAX: The Syntax is date [options] [+format] [date] 7.echo COMMAND: echo command prints the given input string to standard output. SYNTAX: The Syntax is echo [options..] [string]

4. 8.grep COMMAND: grep command selects and prints the lines from a file which matches a given string or pattern. SYNTAX: The Syntax is grep [options] pattern [file] 9.hostname COMMAND: hostname specifies the name of the host. SYNTAX: The Syntax is hostname [-a | -d | -f | -h | -i | -s] 10.head COMMAND: head command is used to display the first ten lines of a file, and also specifies how many lines to display. SYNTAX: The Syntax is head [options] filename

5. 11.hostid COMMAND: hostid command prints the numeric identifier or id of the current host in hexadecimal. SYNTAX: The Syntax is Hostid 12.id COMMAND: id command prints the effective(current) and real userid(UID)s and groupid(GID)s. SYNTAX: The Syntax is id [options] 13.kill COMMAND: kill command is used to kill the background process. SYNTAX: The Syntax is kill [-s] [-l] %pid

6. 14.last COMMAND: last command is used to display the last logged in users list. Last logged in users informations are read from the file /var/log/wtmp. SYNTAX: The Syntax is last [options] 15.ls COMMAND: ls command lists the files and directories under current working directory. SYNTAX: The Syntax is ls [OPTIONS]... [FILE] 16.man COMMAND: man command which is short for manual, provides in depth information about the requested command (or) allows users to search for commands related to a particular keyword. SYNTAX: The Syntax is man commandname [options]

7. 17.mkdir COMMAND: mkdir command is used to create one or more directories. SYNTAX: The Syntax is mkdir [options] directories 18.mv COMMAND: mv command which is short for move. It is used to move/rename file from one directory to another. mv command is different from cp command as it completely removes the file from the source and moves to the directory specified, where cp command just copies the content from one file to another. SYNTAX: The Syntax is mv [-f] [-i] oldname newname 19.passwd COMMAND: passwd command is used to change your password. SYNTAX: The Syntax is passwd [options]

8. 20.pwd COMMAND: pwd - Print Working Directory. pwd command prints the full filename of the current working directory. SYNTAX: The Syntax is pwd [options] 21.rm COMMAND: rm linux command is used to remove/delete the file from the directory. SYNTAX: The Syntax is rm [options..] [file | directory] 22.rmdir COMMAND: rmdir command is used to delete/remove a directory and its subdirectories. SYNTAX: The Syntax is rmdir [options..] Directory

10. 23.sort COMMAND: sort command is used to sort the lines in a text file. SYNTAX: The Syntax is sort [options] filename 24.Shutdown COMMAND: Shutdown - Turn off the computer immediately or at a specified time. SYNTAX: The Syntax is /sbin/shutdown [-t sec] [-arkhncfFHP] time [warning-message] 25.tail COMMAND: tail command is used to display the last or bottom part of the file. By default it displays last 10 lines of a file. SYNTAX: The Syntax is tail [options] filename

11. 26.useradd COMMAND: useradd - Adds new user to the linux system, with specified user-name. When a new user is added then a corresponding entry is made in files /etc/passwd, /etc/group and /etc/shadow SYNTAX: The Syntax is useradd [options] [username] 27.who COMMAND: who command can list the names of users currently logged in, their terminal, the time they have been logged in, and the name of the host from which they have logged in. SYNTAX: The Syntax is who [options] [file] 28.whois COMMAND: whois command lists the information about the domain owner of the given domain. SYNTAX: The Syntax is whois [option] query

12. 29.alias COMMAND: alias command allows you to create a shortcut to a command. As the name indicates, you can set alias/shortcut name for the commands/paths which is too longer to remember. SYNTAX: The Syntax is alias [options] [ AliasName [ =String ] ] 30.file COMMAND: file command tells you if the object you are looking at is a file or a directory. SYNTAX: The Syntax is file [options] directoryname/filename 31.find COMMAND: find command finds one or more files assuming that you know their approximate filenames. SYNTAX: The Syntax is find path [options] .

13. 32.free COMMAND: free command displays information about free and used memory on the system. SYNTAX: The Syntax is free [options] [-V] 33.finger COMMAND: finger command displays the user's login name, real name, terminal name and write status (as a ''*'' after the terminal name if write permission is denied), idle time, login time, office location and office phone number.. SYNTAX: The Syntax is finger [-lmsp] [user ...] [user@host ...] 34.fgrep COMMAND: fgrep command is used to search one or more files for lines that match the given string or word. fgrep is faster than grep search, but less flexible: it can only find fixed text, not regular expressions. SYNTAX: The Syntax is fgrep [options] pattern [file]

14. 35.fg COMMAND: fg command is used to place a job in foreground. SYNTAX: The Syntax is fg [specify job] 36.fdisk COMMAND: fdisk command is used for partition table manipulator. Hard disks can be divided into one or more logical disks called partitions. SYNTAX: The Syntax is fdisk [options] 37.lastlog COMMAND: lastlog command is used to print the last login times for system accounts. Login information is read from the file /var/log/lastlog. SYNTAX: The Syntax is lastlog [options]

15. 38.less COMMAND: less command is used to display text in the terminal screen. It just prints the text in the given file, you cannot edit or manipulate the text here. To display the file from the specified line, enter the line number followed by colon(:). It allows Forward and backward movement in the file. SYNTAX: The Syntax is less [options] filename 39.link COMMAND: link command is used to create a link to a file. It is also called as hard link. Inode will be same for source and destination. SYNTAX: The Syntax is link existingfilename newfilename (or) link source destination 40.ln COMMAND: ln command is used to create link to a file (or) directory. It helps to provide soft link for desired files. Inode will be different for source and destination. SYNTAX: The Syntax is ln [options] existingfile(or directory)name newfile(or directory)name

16. 41.chmod command - change file mode bits SYNTAX chmod [OPTION]... MODE[,MODE]... FILE... 42. cmp command - compare two files byte by byte SYNTAX cmp [OPTION]... FILE1 [FILE2 [SKIP1 [SKIP2]]] 43. cmp command - compare two files byte by byte SYNTAX cmp [OPTION]... FILE1 [FILE2 [SKIP1 [SKIP2]]] 44. write command — send a message to another user SYNTAX write user [ttyname]

17. 45.ssh command — OpenSSH SSH client (remote login program) SYNTAX ssh [-1246AaCfgKkMNnqsTtVvXxY] 46.whoami command - print effective userid SYNTAX whoami [OPTION]... 47. lpr command - print files SYNTAX lpr [ -E ] [ -H server[:port] ] [ -U username ] [ -P destination[/instance] ] [ -# num-copies [ -h ] [ -l ] [ -m ] [ -o option[=value] ] [ -p] [ -q ] [ -r ] [ -C/J/T title ] [ file(s) ]

18. 48. vim command - Vi IMproved, a programmers text editor SYNTAX vim [options] [file ..] 49. THE ping COMMAND ping, ping6 - send ICMP ECHO_REQUEST to network hosts 50.THE wall COMMAND wall — write a message to users SYNTAX wall [file]