Sunday, 23 December 2012

Basic Unix commands

Basic UNIX commands :-
• To change the current directory to another directory
                     Syntax-          cd [path_of_directory]
Note: - UNIX is case sensitive so type the same directory name
                                              [localhost@root ~]$ cd /home/user/data
                                              [localhost@root data]$
• To change the current directory to your home directory
                     Syntax-         cd
                                              [localhost@root data]$ cd
                                              [localhost@root ~]$
Note: - The current directory should now be your home directory.
• To create a directory inside the current directory
                     Syntax-           mkdir [name_of_new_directory]
                                               [localhost@root ~]$ mkdir test
              Test directory now should exist within the current directory.
• The cp command is use to make a copy of a file
                     Syntax-           cp [name of file] [name of copy]
                                               [localhost@root ~]$ cp old_directory  new_directory_name
 mv command is used to either rename an existing file or folder to something different
                or to “move” a file from one directory to another.
                     Syntax-           mv [name of existing file] [new name for existing file]
                                              [localhost@root ~]$ mv name_of_existing_file new_name_for_existing_file
• To move an existing file, type
                     Syntax-           mv [name of existing file] [path of new location]
                                               [localhost@root inteljasper]$ mv file_name  path_where_to_copy
                                               [localhost@root ~]$ mv mydir  /home/localhost/test/
• rm command is used to delete a file, to remove an existing file, type
                     Syntax-         rm [name of file]
                                              [localhost@root ~]$ rm  file_name
• rmdir command is a separate command for removing directories. To remove a directory, the directory must be empty. To remove an existing directory, type
                     Syntax-          rmdir [name of directory]
                                                 [localhost@root ~]$ rmdir directory_name
Some basic useful commands and there output: -

• date
                     Syntax-           [localhost@root~]$date
                     Output -         Fri Dec 23 10:30:05 IST 2011
• tput clear - To clear the screen clear is an argument of tput command.
                     Syntax-           [localhost@root~]$ tput clear   
• cal – Calendar of current month
                     Syntax-            [localhost@root~]$ cal     
• cal 1 1987 – to see the calendar of January 1987
                     Syntax-           [localhost@root~]$ cal 1 1987    
• who – to see who are the users? It will show all the users who are currently logged in.
                     Syntax-          [localhost@root~]$ who           
                     Output-          localhost   pts/1        2011-12-23 10:29 (sharad-pc.home)
• ps – to view the running process
                     Syntax-          [localhost@root~]$ps             
                     Output-          PID TTY          TIME CMD
                                                  14493 pts/1    00:00:00 bash
                                                  14691 pts/1    00:00:00 ps
• ksh -
                     Syntax-          [localhost@root~]$ksh             Korn shell it will show only like this
                     Output -        $
                     Syntax-          $ sh                                                   Bourne shell(sh-3.2$)
                     Syntax-          $ csh                                                 C shell
                     Syntax-          $bash                                                Bash  shell(original shell)
                     Output-         [localhost@root~]$
• ls – to list all the files
                     Syntax-         [localhost@root~]$ls            
                           files are arranged alphabetically with uppercase having      precedence over lower case)
 •  ls chap*
                     Syntax-        [localhost@root~]$ls chap*      
                            It will list all files starting with chap word
  ls –l chap*
                     Syntax-       [localhost@root~]$ls -l chap*  
                     Output-       -rw-rw-r-- 1 localhost localhost    286 Dec 19 12:20 list
  ls > list
                     Syntax-        [localhost@root~]$ls > list     
                               Directing output to a file name list. Prompts return no display on the terminal (">" is a                     
                               metacharacters )
  cat list  - to open any file
                     Syntax-         [localhost@root~]$cat list         
                                                       list is a file name where all the list of files are stored you can give any name.
  wc list  -
                     Syntax-          [localhost@root~]$wc list              Counting number of lines in a file
                     Output-           6   6   42 list                  means 6 lines,6words,42 character
•  ls | wc -  Feeding output of one command to another using "|"pipeline
                      Syntax-         [localhost@root~]$ls | wc   or
• Programing with the shell
                    You can assign a value to a variable at the prompt
                      Syntax-         [localhost@root~]$ x=5             
                     No space on either side of = and then evaluate the value of this variable with the echo command
                      Syntax-         [localhost@root~]$ echo $x
                      Output-        op/  5
• Exit : signing off
                      Syntax-          [localhost@root~]$exit         
                                 Or                    [localhost@root~]$logout
                    Syntax-         [localhost@root~]$echo sharad            gupta
                      Output-          o/p   sharad gupta
                      Syntax-          [localhost@root~]$echo $PATH
                      Syntax-          [localhost@root~]$type ls
                      Output-           ls is aliased to `ls --color=tty'
                      Syntax-         [localhost@root~]$type echo      to know which command it is
                      Output-          echo is a shell builtin
•  Combined commands
                      Syntax-         [localhost@root~]$wc list; ls -l list
                      Output-        18  18 289 list
                                                          -rw-rw-r-- 1 localhost localhost 289 Dec 19 12:26 list

•  Save the results in new file
                      Syntax-         [localhost@root~]$ ( wc test ; ls -l test ) > newlist
•  To know about any command
                      Syntax-         [localhost@root~]$man -k awk
                      Output-         English              (3pm)  - use nice English (or awk) names for ugly  
                                                             punctuation variables
                                                            a2p                  (1)  - Awk to Perl translator
                                                           awk                  (1p)  - pattern scanning and processing language
                                                          gawk                 (1)  - pattern scanning and processing language
                                                           gawk                (rpm) - The GNU version of the awk text processing utility.

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