Unix / Linux - Useful Commands

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This quick guide lists commands, including a syntax and a brief description. For more detail, use −

$man command

Files and Directories

These commands allow you to create directories and handle files.

Given below is the list of commands in Files and Directories. Sr.No. Command & Description 1 cat Displays File Contents 2 cd Changes Directory to dirname 3 chgrp Changes file group 4 chmod Changes permissions 5 cp Copies source file into destination 6 file Determines file type 7 find Finds files 8 grep Searches files for regular expressions 9 head Displays first few lines of a file 10 ln Creates softlink on oldname 11 ls Displays information about file type 12 mkdir Creates a new directory dirname 13 more Displays data in paginated form 14 mv Moves (Renames) an oldname to newname 15 pwd Prints current working directory 16 rm Removes (Deletes) filename 17 rmdir Deletes an existing directory provided it is empty 18 tail Prints last few lines in a file 19 touch Updates access and modification time of a file

Manipulating data

The contents of files can be compared and altered with the following commands.

Given below is the list of commands in Manipulating data. Sr.No. Command & Description 1 awk Pattern scanning and processing language 2 cmp Compares the contents of two files 3 comm Compares sorted data 4 cut Cuts out selected fields of each line of a file 5 diff Differential file comparator 6 expand Expands tabs to spaces 7 join Joins files on some common field 8 perl Data manipulation language 9 sed Stream text editor 10 sort Sorts file data 11 split Splits file into smaller files 12 tr Translates characters 13 uniq Reports repeated lines in a file 14 wc Counts words, lines, and characters 15 vi Opens vi text editor 16 vim Opens vim text editor 17 fmt Simple text formatter 18 spell Checks text for spelling error 19 ispell Checks text for spelling error 20 emacs GNU project Emacs 21 ex, edit Line editor 22 emacs GNU project Emacs

Compressed Files

Files may be compressed to save space. Compressed files can be created and examined.

Sr.No. Command & Description 1 compress Compresses files 2 gunzip Helps uncompress gzipped files 3 gzip GNU alternative compression method 4 uncompress Helps uncompress files 5 unzip List, test and extract compressed files in a ZIP archive 6 zcat Cat a compressed file 7 zcmp Compares compressed files 8 zdiff Compares compressed files 9 zmore File perusal filter for crt viewing of compressed text

Getting Information

Various Unix manuals and documentation are available on-line. The following Shell commands give information −

Sr.No. Command & Description 1 apropos Locates commands by keyword lookup 2 info Displays command information pages online 2 man Displays manual pages online 3 whatis Searches the whatis database for complete words 4 yelp GNOME help viewer

Network Communication

These following commands are used to send and receive files from a local Unix hosts to the remote host around the world.

Sr.No. Command & Description 1 ftp File transfer program 2 rcp Remote file copy 3 rlogin Remote login to a Unix host 4 rsh Remote shell 5 tftp Trivial file transfer program 6 telnet Makes terminal connection to another host 7 ssh Secures shell terminal or command connection 8 scp Secures shell remote file copy 9 sftp Secures shell file transfer program

Some of these commands may be restricted at your computer for security reasons.

Messages between Users

The Unix systems support on-screen messages to other users and world-wide electronic mail −

Sr.No. Command & Description 1 evolution GUI mail handling tool on Linux 2 mail Simple send or read mail program 3 mesg Permits or denies messages 4 parcel Sends files to another user 5 pine Vdu-based mail utility 6 talk Talks to another user 7 write Writes message to another user

Programming Utilities

The following programming tools and languages are available based on what you have installed on your Unix.

Given below is the list of tools and languages in Programming Utilities. Sr.No. Command & Description 1 dbx Sun debugger 2 gdb GNU debugger 3 make Maintains program groups and compile programs 4 nm Prints program's name list 5 size Prints program's sizes 6 strip Removes symbol table and relocation bits 7 cb C program beautifier 8 cc ANSI C compiler for Suns SPARC systems 9 ctrace C program debugger 10 gcc GNU ANSI C Compiler 11 indent Indent and format C program source 12 bc Interactive arithmetic language processor 13 gcl GNU Common Lisp 14 perl General purpose language 15 php Web page embedded language 16 py Python language interpreter 17 asp Web page embedded language 18 CC C++ compiler for Suns SPARC systems 19 g++ GNU C++ Compiler 20 javac JAVA compiler 21 appletvieweir JAVA applet viewer 22 netbeans Java integrated development environment on Linux 23 sqlplus Runs the Oracle SQL interpreter 24 sqlldr Runs the Oracle SQL data loader 25 mysql Runs the mysql SQL interpreter

Misc Commands

These commands list or alter information about the system −

Given below is the list of Misc Commands in Unix. Sr.No. Command & Description 1 chfn Changes your finger information 2 chgrp Changes the group ownership of a file 3 chown Changes owner 4 date Prints the date 5 determin Automatically finds terminal type 6 du Prints amount of disk usage 7 echo Echo arguments to the standard options 8 exit Quits the system 9 finger Prints information about logged-in users 10 groupadd Creates a user group 11 groups Show group memberships 12 homequota Shows quota and file usage 13 iostat Reports I/O statistics 14 kill Sends a signal to a process 15 last Shows last logins of users 16 logout Logs off Unix 17 lun Lists user names or login ID 18 netstat Shows network status 19 passwd Changes user password 20 passwd Changes your login password 21 printenv Displays value of a shell variable 22 ps Displays the status of current processes 23 ps Prints process status statistics 24 quota -v Displays disk usage and limits 25 reset Resets terminal mode 26 script Keeps script of terminal session 27 script Saves the output of a command or process 28 setenv Sets environment variables 30 stty Sets terminal options 31 time Helps time a command 32 top Displays all system processes 33 tset Sets terminal mode 34 tty Prints current terminal name 35 umask Show the permissions that are given to view files by default 36 uname Displays name of the current system 37 uptime Gets the system up time 38 useradd Creates a user account 39 users Prints names of logged in users 40 vmstat Reports virtual memory statistics 41 w Shows what logged in users are doing 42 who Lists logged in users