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Unix
 

Unix

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    Unix Unix Presentation Transcript

    • Introduction to UNIX Ke Liu http://www.cs.binghamton.edu/~kliu/cs350/ [email_address]
    • Topics.
      • Logging in.
      • Unix Shells and useful shell commands.
      • File System in Unix.
      • Program, Process and Process control.
      • Inter-process communication.
      • Compiling and debugging C programs.
      • Editors.
    • UNIX
      • UNIX is multi-user and multi-tasking operating system.
      • Multi-tasking: Multiple processes can run concurrently.
      • Example, different users can read mails, copy files, and print all at once.
    • Logging In
      • Enter login name and password !
      • System password file: /etc/passwd (usually).
      • You can change password using the command: passwd.
    • Shell
      • After a successful login, the shell program is run. The default shell of bingsuns: tcsh
      • bingsun2% ps
      • PID TTY TIME CMD
      • 2159 pts/2 0:00 tcsh
      • Shell is a command line interpreter that reads user commands and executes them.
    • Unix Shells
      • Common Shells: Bourne shell, the C shell, and the Korn shell.
      • The shell on bingsuns is tcsh (tc shell).
      • Users can switch between shells, using the commands bash, csh, ksh, sh.
      • Control D (^d) to return back to original shell, or just use the command: exit.
    • Some shell commands
      • Most Important command: man (manual pages).
      • Help: unix commands, C functions.
      • Usage: man <command/function>
      • Try “man man” !
      • Example:
      • man ls, man passwd, man printf.
    • Some shell commands (cont’)
      • pwd: working directory (/u0/users/2/kliu1).
      • ls: list contents of directory
      • mkdir <dir-name>: make directory
      • rmdir <dir-name>: remove an empty directory
      • rm –r <dir-name>: remove a directory with all the contents
      • cd <directory>: change directory, ~/ means your home directory
      • cp <source> <target>: copy command.
    • Some shell commands (cont’)
      • chmod <mode> <filename>: change mode of a file/directory
      • ls –l <directory or filename>: long list with details
      • 9 permission bits: d r w x r w x r w x
      • 3 categories: user/group/all.
      • Permissions: read/write/execute (r/w/x).
      • E.g.: mode= 644 means r w _ r_ _ r _ _
      • command: chmod 644 <filename>
      • first 3 bits for user. Next group. Next all others.
    • Some shell commands (cont’)
      • rm <option> <filename>: remove files
      • e.g.: rm –fr directory/filename
      • mv <old> <new>: change the name of a file
      • Pipes: Connect the stdout of one command with the stdin of another command
      • e.g.: ls -l | more or ls –l | less
    • File System
      • Hierarchical arrangement of files and directories.
      • Top level: root or /
      • e.g.: cd /
      • . Current directory, .. One level higher directory
      • e.g.: cd . No change for it is current directory
      • or cd .. Change to parent directory.
    • File System (cont’)
      • Pathname: absolute and relative.
      • Absolute pathname: /u0/users/2/kliu1
      • Relative pathname: abc.
    • Editors.
      • Different editors: emacs, pico, vi
      • emacs <filename>
      • pico <filename>
      • vi <filename>
    • The easiest editor: pico or nano
      • pico <filename>
      • Full screen editor
      • Help on the bottom of the screen
      • The nano is an extension to the pico
    • Basic operations in pico
      • Ctrl + v : to move page down
      • Ctrl + y : to move page up
      • Ctrl + o : to save the current buffer
      • Ctrl + x : to exit with or without saving
      • Ctrl + g : to get help
      • Ctrl + r : to open a file
      • Ctrl + w : to find a string in the current buffer
      • Ctrl + c : to get the current position in the buffer
    • Program & Process
      • Program is an executable file that resides on the disk.
      • Process is an executing instance of a program.
      • A Unix process is identified by a unique non-negative integer called the process ID.
      • Check process status using the “ps” command.
    • Foreground/background processes
      • A program run using the ampersand operator “&” creates a background process.
      • E.g.:
      • bingsun2% back &
      • otherwise it creates a foreground process.
      • E.g.:
      • bingsun2% back
    • Foreground/background processes
      • Only 1 foreground process for each session. Multiple background processes.
      • Where are background processes used?
      • All system daemons, long user processes, etc.
      • e.g. printer-daemon process or mailer-daemon process.
      • These processes are always running in background.
      • Pine is foreground process.
    • Process Status
      • bingsun2% back &
      • [1] 16488 the process id assigned by system
      • bingsun2% ps
      • PID TTY TIME CMD
      • 1973 pts/39 0:01 tcsh
      • 16488 pts/39 0:00 back
    • How to stop a process?
      • Foreground processes can generally be stopped by pressing CONTROL C (^C).
      • Background processes can be stopped using the kill command.
      • Usage: kill SIGNAL <process id list>
      • kill -9 <process id list> (-9 means no blocked)
        • Or kill <process id list>.
      • If a foreground process is not stopping by ^C, you can open another session and use the kill command.