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intro unix/linux 02



touring essential programs

touring essential programs



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    intro unix/linux 02 intro unix/linux 02 Presentation Transcript

    • Lesson 2-Touring Essential Programs
    • Overview
      • Development of UNIX and Linux.
      • Commands to execute utilities.
      • Communicating instructions to the shell.
      • Navigating the file system.
      • Examining and managing files.
      • Accessing the programmer’s manual.
      • Accessing Internet resources.
    • Development of UNIX and Linux
      • UNIX os, developed in 1970s at Bell Laboratories, features:
          • main program, called kernel , to control CPU and other hardware.
          • collection of user and system programs called utilities .
          • structure, called file system , for keeping and locating data on hard drive.
          • Unix was a multi-user and multi-tasking os
    • Development of UNIX and Linux
      • Linus Torvalds wrote a UNIX look-alike operating system called Linux .
      • The operating system is available for free in its basic form for download, or at a low cost from several distributors.
      • fundamental programs in Linux employ same code , but different distributors add special features and installation programs.
      • Some of different flavors of Linux operating system are RedHat, Lindows, SuSe, Mandrake, etc.
      Development of UNIX and Linux
    • Commands to Execute Utilities
      • Introduction to the shell.
      • Issuing commands to a shell.
      • Passing information to a utility.
      • Listing processes.
    • Introduction to the Shell
      • shell: program which displays prompt on screen.
      • shell reads instructions of user and interprets them to the remainder of the system.
      • Usually $ sign is the prompt in many systems.
      • shell processes and executes command keyed in by user.
    • Issuing Commands to a Shell
      • Various utilities can be executed from the shell prompt.
      • “ whoami ” utility displays user’s login name or username on screen.
      • “ date ” utility displays current date and time on screen.
      • “ hostname ” utility display name of system user working on.
    • Issuing Commands to a Shell
      • “ clear ” utility to clear all text on screen and display the prompt at top of screen or window.
      • Delete or Ctrl-H to correct errors that occur while entering commands.
      • “ who ” utility to display list of users currently logged on.
    • Issuing Commands to a Shell Output of who Command
    • Issuing Commands to a Shell
      • port: physical location at back of computer.
      • Each port has designation- usually begins with tty and number
      • terminal connected through network uses electronic or pseudo port named pts .
    • Issuing Commands to a Shell
      • command/utility keyed in by a user is followed by the ENTER key.
      • shell interprets ENTER as end of command/utility.
      • shell starts child process to execute command/utility.
    • Issuing Commands to a Shell
      • shell locates path of utility/command and executes it.
      • output, by default, connected to screen, unless redirect it.
      • After executing command/utility, it returns command prompt again.
    • Issuing Commands to a Shell How the shell works
    • Passing Information to a Utility
      • When information passed to a utility, shell runs utility, and passes information that comes after the command to utility.
      • Information passed to utility called argument .
      • Arguments provide instructions to utilities.
      • Multiple arguments can also be passed to a utility.
    • Passing Information to a Utility
      • “ cal ” program provides users current month’s calendar.
      • Multiple arguments can be passed to cal utility.
      • When two arguments are passed to cal program, the program interprets first argument as month and second as year.
    • Passing Information to a Utility
      • “ look ” command to locate words in dictionary file that begin with that word, and output all matching words.
      • look command requires one argument – word to locate.
    • Listing Processes
      • A process is an instance of a running program code.
      • “ ps ” command to list all current processes, with some info about each process.
      • output displays process id , port , CPU time , and code process is running.
    • Listing Processes
      • “ – aux ” and “ –ef ” options used with “ ps ” command to display processes running on entire system, including system processes, and list of currently logged on users.
      • Arguments that begin with minus (-) sign are options .
      • ps option useful for sys-admin trouble-shooting system.
    • Communicating Instructions to the Shell
      • Every user is given a place, called home directory , to work with and save files.
      • home directory: default workspace of user.
      • home directory contains names of files and subdirectories created by and owned by a user.
    • Communicating Instructions to the Shell
      • Working with files.
      • Redirecting output from a utility.
      • Determining the role of tokens on command-lines.
      • Starting a child shell.
      • Reissuing commands.
      • Using nicknames for commands.
    • Working with Files
      • “ ls ” (list) command lists contents of current directory’s standard files.
      • “ more ” command displays contents of file one part at a time.
      • command requires one argument – name of the file.
      • spacebar: display additional text in file displayed by more.
      • “ q ” key can to quit ‘ more ’ utility.
      • “ wc ” ( word count ) utility: count number of lines, words, and characters in file.
      • command requires one parameter – name of the file.
      Working with Files
    • Working with Files
      • “– l” option used with wc command to only count number of lines in file.
      • “ -c” option: count characters in file.
      • “ -w” option : count number of words in file.
    • Redirecting Output from a Utility
      • By default, results provided by any utility are displayed on user’s screen.
      • Instructions can be given to redirect output of utility to file.
      • command- redirect output of file: “utility > filename” .
      • > is instruction to redirect output to new file
    • Redirecting Output from a Utility
      • double redirect (>>): append output of utility to end of existing file
      • | (pipe) command: redirect output of one utility to another utility.
      • The argument following the pipeline must be a utility.
    • Determining the Role of Tokens on Command-Lines
      • Each word or object on a command-line is called a token .
      • shell is programmed to read initial token as utility program to run or some action to take
      • location on command-line determines how shell interprets each token.
    • Starting a Child Shell List of Various Shells in UNIX/Linux
    • Reissuing Commands
      • “ !!” command or “r” command: re-execute previously entered command.
      • “ !!” command works only on csh , tch , or bash shell.
      • The “r” command works only on a Korn shell.
      • The sh shell does not allow user to re-execute previously entered commands.
    • Reissuing Commands
      • Up arrow key: display previously entered commands one at a time.
      • shell keeps track of commands we issue at prompt.
      • “ history ” command: list all commands entered previously, and every command has a number associated with it.
    • Reissuing Commands Various Options to Execute Previous Commands
    • Using Nicknames for Commands
      • An “ alias ” or alternate name used for commands hard to remember.
      • alias command can list all current aliases.
      • command “ unalias alias name ” can remove an alias.
    • Using Nicknames for Commands Nicknames for commands in UNIX/Linux Command Shell alias alias name utility name Csh and tch alias alias name=utility name Bash and ksh
    • Navigating the File System
      • arrangement of files and folders in system: file system
      • “ pwd ” ( present working directory ) command can get location of user’s home directory
      • result displays path from root to present working directory
      • topmost directory: “ root ” (identified as / )
      • “ ls / ” command can obtain a list of all files and directories in root directory
      Navigating the File System
    • Navigating the File System
      • “ mkdir ” ( make directory ) command: create new directory
      • command requires 1 argument – name to give to directory
      • “– F” option used with ‘ ls ’ command to include a / (slash) after all directory names and also to identify other kinds of files.
    • Navigating the File System
      • “ cd ” command can make directory the current directory.
      • command requires 1 parameter – name of directory to become current directory
      • cd command: return to home directory. no required parameters
    • Examining and Managing Files
      • Find matching text:
        • A particular word in a file can be located by giving the command “ /word to be located ” .
        • “ n ” key can locate next instance of same word in file.
        • “ b ” key can be used to move one screen backwards.
    • Examining and Managing Files
      • “ head ” utility: read first 10 lines of file
      • “ tail ” utility”: view last 10 lines of file
      • Both utilities require 1 argument – name of file to read
      • number of lines to read can be passed as argument to utilities.
    • Examining and Managing Files
      • cat utility: view entire contents of file
      • utility requires 1 argument – name of file to read.
      • utility is preferable when file small
    • Examining and Managing Files
      • Copy files:
        • “ cp ” command: make copy of existing file, as well as copy files to another subdirectory.
        • 2 arguments are required to duplicate file – name of existing file and name to give duplicated file.
        • arguments required to copy file to another subdirectory are – name of file to copy and target directory
    • Examining and Managing Files
      • Removing files:
        • “ rm ” command: delete file
        • command requires 1 argument – name of file to delete
    • Examining and Managing Files
      • Removing files (cont):
        • rm command does its work and displays prompt. It displays no message.
        • “ -i” option: ask for confirmation before deleting any filenames listed as an argument.
        • command also accepts multiple file names as arguments.
    • Examining and Managing Files
      • Renaming files:
        • “mv” command: rename files, as well as move files from one location to another.
        • 2 arguments are required while renaming files – current name of file and new name to give file
        • arguments required for moving files – name of files to move and destination directory
    • Examining and Managing Files
      • Deciphering utility error messages:
        • Error messages due to failure of utility are shown in screen by default.
        • Every process has " output door ", where it writes output, and an error door, where it writes error messages.
        • By default, " error door " connected to screen unless we redirect it.
    • Examining and Managing Files
      • Printing file:
        • “ lp ” or “ lpr ” command: print file
        • command requires 1 argument – name of file to print.
        • “– P” option with “ lpr ” command, and “-d” option with the lp command, can specify name of printer to use
    • Accessing the Programmer’s Manual
      • UNIX and Linux systems include extensive collection of powerful utility programs, system features, application languages, and support libraries.
      • The UNIX programmer’s manual provides info needed to employ exact syntax of a particular option or command format for a utility.
    • Accessing the Programmer’s Manual
      • manual contains detailed documentation on use and function of utility programs, application programs, and libraries.
      • manual also contains info on UNIX system files and system programming libraries.
      • includes supplementary info on related special files and commands for each entry.
    • Accessing the Programmer’s Manual
      • man command: provide online manual entry for utility or command
      • command requires 1 argument – name of utility or command
      • “ man –k” command: search manual pages’ descriptions for keywords.
    • Accessing Internet Resources
      • Internet includes many useful sites that provide info on:
          • Recent news in Linux world (www.linux.org/www.linux.com).
          • Interactive Web tutorials
          • Recent software updates and Linux code documentation.
    • Summary
      • shell: process that interprets commands entered by user
      • Each word or object on command-line: token
      • All shells, except for sh, allow users to create alias names for commands
      • file system: collection of files and folders
    • Summary
      • We can work on many utilities, print files, and access system folders from a shell.
      • Files can be printed from shell prompt.
      • Online manual pages provide detailed description of system utilities, files, and functionalities.
      • Internet includes useful sites that provide info on various aspects of UNIX and Linux.