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Commands - Seneca

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					                             Agenda
   Chapter 1: Linux (Unix) Features
   Commands (Chapters 2 & 3)
       Command Structure / Command line editing
       man, passwd, cal, date, whereis, which
       Working with Files:
            file, cat, more, less, grep, head, tail, cp, mv, ls
            sort, uniq, diff
       Communicating with Users
            who, talk, write, mesg, finger
                Unix Structure
The Linux operating system can be visualized
in terms of layers:
   Unix Kernel
        controls the computer resources and schedules jobs
   Shell
        acts as a command interpreter that acts as an interface
         between users and the operating system
   Utilities (Commands)
        comprehensive set of utilities that are universally
         required by Unix administrators & users. Utilities are
         often referred to as commands
                         Linux Structure
    Calendar systems                             Compilers

Inventory control                                     Mail & message
    systems                                              facilities

                             Hardware
                                                        Interpreters
 Formatters

                            Linux Kernel
   Spreadsheet                                        Database Mgmt
                          The shell & other               System
   applications            basic utilities
                       Editors                Word processors
         Utilities (Commands)
   For the remainder of this course, utilities and
    commands are considered the same.
   Linux commands are usually typed in
    lowercase followed by an argument (or
    arguments)
   Pressing ENTER or RETURN signals that you
    have completed giving an instruction and that
    you are ready for the OS to execute the
    command or respond to your message
Linux (Unix) Command Format
 command [arg 1] [arg 2] … [arg n]

    An argument is a filename, string or text, or some
     other object that a command acts upon
    An option is also an argument that modifies the
     effect of a command
    A space, a number of spaces, or a tab can be used
     to separate command from argument, or separate
     arguments.
          Correcting Mistakes
You can correct mis-typed command
prior to pressing ENTER or RETURN
   Erase Characters
        Backspace or CTRL-Backspace or CTRL-h
   Delete a Word
        CTRL-w
   Delete an Entire Line
        CTRL-u
          Correcting Mistakes
   Aborting Program Execution
        DELETE or CTRL-c

   Recalling Previous Commands
        Depends on shell & .profile setup

        Phobos (check .profile for VISUAL variable):
            if  VISUAL=vi <ESC><K> (K - up, J - down)
            if  VISUAL=emacs <CTRL><P>
        Gothic:
              Up arrow , Down arrow
                     man
A comprehensive online manual for common
UNIX commands
format:
  man [options] command
  Options:
    -k  provides short (one-line) explanation relating
        to the commands matching the character string
    eg. man -k mkdir
               passwd
Used to change existing password
format:
  passwd [options]

  Options:
    -f  changes the user information accessed by
    the
         finger command
                         cal
Used to display a calendar
Format:
    cal [month] [year]        (calendar for specified month &
    year)

    cal                    (displays calendar for current month)



   eg.     cal 12 2000
            (displays calendar month of December Year 2000)
                      date
Used to display or set the time & date
Format:
    date [option] [+format]

   +format argument specifies format of display
   After the + sign, can specify (within quotes) text
    as well as % followed by a field descriptor to
    indicate how date will be displayed
                               date
   Popular Field Descriptors:
          %A    Full Weekday name %d Number of day
          %B    Full month name       %m Number of month
          %y    Last 2 digits of year %Y 4-digit-year
          %I     Hour                 %H Hour (Military time)
          %M    Minutes               %S Seconds
          %n     New Line             %r h:m:s with am or pm

          eg.    date +”Today is %A” (note no space between + and “)


          %n is used to advance to the next line
          whereis / which
whereis is a utility that lists all directory paths
that contains command or program
For Example: whereis mv

which is a utility that lists only the directory
path that the shell will run the command or
program (used to help avoid confusion if
more that 1 command but perform
differently. Example: which mv
         Working with Files
   file, cat, more, less
   grep, head, tail
   cp, mv, ls
   sort, uniq, diff
                    file
Used to classify the type of file: ASCII
(text) or executable (binary)

Format:
file [options] file-list
                        cat
Used to combine contents multiple files
(“catenate” means to join together). Can be
used to display contents of one file
format:
  cat [options] [file-list]

  *Refer to on-line manual regarding options for
   cat command
                         more
Displays a file, one screenful (spacebar) at a
time or scroll one line at a time (RETURN)
format:
  more [options] [file-list]
  Options:
     -d    prompts user to continue at bottom of screen
          note: when searching for text within more process,
          user can type k/pattern? ENTER to initiate text search. In
          addition u for page up, d for down (can also use numbers
          to indicate amount of movement)
                     less
Less is a program similar to more, but
which allows backward movement in
the file as well as forward movement
(more movement options than more)

Format:
less [options] [file-list]
Please refer to online manual for movement options
                       grep
Used to search for a pattern which is stored
in a file or files.
Format:
  grep [options] pattern [file-list]
  Options:
     -c displays # of lines that contains a match
     -i ignores case sensitivity
     -n displays line number of file that contains a
         match
     -l displays only name of file that contains a match
                    head
Display the beginning lines of a file

format:
  head [-number] [file-list]

  * “-number” indicates the number of lines
    (from the beginning of the file) that you want
      to have displayed
                     tail
Displays the tail or ending lines of a file

format:
  tail [-number] [+number] [options] [file]

  * “-number” indicates the number of lines
    (from the bottom of the file) that you want
      to have displayed. “+number” indicates line
      number to display until end (tail) of file
                     cp
Used to copy one or more files
format:
  cp [options] sourcefile destinationfile

  Options:
    -r   subdirectories & contents are copied
    -i   prompts user to overwrite existing file
                        mv
Used to move or rename files
format:
  mv [options] oldfilename newfilename
  mv [options] existingfile-list directory
  mv [options] existingdirectory newdirectory

  Options:
    -i   prompts user to overwrite existing file
                             ls
Used to display information regarding a file or
directory
format:
  ls [options] [file-list]
  Options:
     -a     short display of all files (incl. hidden files)
     -l    detailed display of files (excl. hidden files)
     -al   detailed display of all files
     -F      displays / after directory, * after executable
             file
                     sort
Used to sort or merge files. Particularly
useful as a filter to sort standard input.
Format:
  sort [options] [field-specifier-list][file-list]
Examples
  sort output.txt
  who | sort | more
  ls | sort > listing.txt
                        uniq
Used to display lines from a file that are
unique. Used after a sort, uniq will only
display total “unique” lines of text

  uniq [options] [inputfile] [outputfile]

     Options:
     -c preceed line with # of occurrence line in input file
     -d display only lines that are repeated
     -u display only lines that are not repeated
                       diff
Displays the differences between two
files. Provides instructions as to editing
steps to make files identical

  diff [options] [file1] [file2]
  diff [options] [directory1] [directory2]

    Options:
    -b ignore blanks
    Communicating with Others
   who
   talk
   write
   mesg
   finger
                     who
Used to display names of users logged into
system
Format:
  who [options]
  who or who am i or            whoami
  Options:
    -H displays head above user information
    -i displays # of minutes user was idle
    -T displays message reception status
                talk / write
   talk allows user to conduct a two-way text-based
    conversation. To initiate talk you type:
    talk phobos_user_id (use who -T to determine if
    user is receiving messages)

   write is used to send a message to another user.
    To send a message, type:
    write phobos_user_id (Mainly used to broadcast a
    message but can be used to chat - user who -T to
    check mesg status first)
                  mesg
Used to “turn on” or “turn-off” reception
of messages from other users.

   To turn on message reception status, type:
    mesg y <ENTER>
   To turn-off message reception status, type:
    mesg n <ENTER>
                     finger
Used to display user names and related
information
format:
  finger [options] [user-list]
  Options:
     -l displays detailed information of all users
     -m matches names specified from user-list
     -q displays short report of users logged on
     -s displays a short report for each user incl.name
                       finger
Interesting point:

   finger utility will display contents in file “.plan” and
    “.project” in the user’s home directory.
   These files are useful to provide additional
    information about the user
    eg.    finger msaul               (In phobos)
            finger jankul            (In phobos)
    Note: you need to set the file permissons to allow
    group & others to read file!

				
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