A Short Unix Tutorial

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A Short Unix Tutorial

• Erdogan Dogdu
• TOBB Ekonomi ve Teknoloji Üniversitesi
• Some material is used from http//csua.berkeley.
  edu

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Outline

• I. getting help
• II. the file system
• III. the shell
• IV. editors
• V. input and output redirection
• VI. process management

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What is it and where do you get it?

• An operating system used on everything from
  servers to embedded systems.
• To you, probably a prompt
• gt type stuff here

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If you know only one thing, know how to read a
manual

• gtman command
• gives you help on that command.
• gtapropos keyword
• tells you all man pages that contain keyword.

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Files and DirectoriesNaming something gives you
power over it.
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Absolute Addressing
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Addressing relative to your home dir.
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Addressing relative to your current dir.
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File system commands

• pwd - report your current directory
• cd ltto wheregt - change your current directory
• ls ltdirectorygt -list contents of directory
• cp ltold filegt ltnew filegt - copy
• mv ltold filegt ltnew filegt - move (or rename)
• rm ltfilegt -delete a file
• mkdir ltnew directory namegt -make a directory
• rmdir ltdirectorygt -remove an empty directory

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getting recursive

• remove a directory and its contents
• rm -r ltdirectorygt
• copy a directory and its contents
• cp -r ltdirectorygt

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File permissions.

• There are 3 kinds of people in the world you
  (user), your friends (group) and everyone else
  (other).
• Each sort of person may or may not be able to
  read, write, or execute a file.
• gtls -l .forward
• -rw-r--r-- 1 darin csua 23 Jan 23 2002
  .forward
• gtls -l .cshrc.local
• -rwxr-xr-- 1 darin csua 2988 May 19 0048
  .cshrc.local

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executing

• executing a file means running it as a program.
• executing a directory means setting your
  current directory to it using cd.

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Changing File Permissions

• make a file readable to your friends
• chmod gr ltfilenamegt
• change who owns a file
• chown ltusergt ltfilenamegt
• change to which group the file belongs
• chgrp ltgroupgt ltfilenamegt

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touch

• look at the full listing again
• gtls -l .forward
• -rw-r--r-- 1 darin csua 23 Jan 23 2002
  .forward
• Each file has a date stamp of when it was
  modified.
• Use touch to set the timestamp to the current
  clock.
• touch ltfilenamegt
• Touch creates the file if it didnt exist
  beforehand.
• You can only touch a file to which you can write.

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Symbolic Links

• use ln -s ltold filegt ltsecond namegt to create a
  symbolic link to a file.
• gtls -l .forward
• -rw-r--r-- 1 darin csua .forward
• lrwxr-xr-x 1 darin csua .forward.link_at_ -gt
  .forward
• The first l tells you that its a symbolic
  link.
• Symbolic links can be used as if it were its
  target.

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whats a shell?

• The shell is the program that
• runs when you log in. It prints
• the prompt and reads what you
• type, invokes programs, etc.
• your window to the Unix world.
• use chsh ltnew shellgt to change your shell

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File Globbing

• some commands can work on many files at once
• gt rm file1 file2 file27
• Use to match any number of unknown characters
• gt rm file
• Use ? to match one unknown character.
• gt rm file?

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(un)aliasing

• create shortcuts for yourself
• gtalias ll ls -la
• Use alias with no arguments to discover current
  aliases
• gtalias
• rm rm -i
• ll ls -la
• Type unalias rm to remove alias.

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shell variables, echo

• (tcsh) gtsetenv BOB joe
• (tcsh) gtprintenv BOB
• joe
• (tcsh) gtecho BOB
• joe

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PATH a very important shell variable

• gtecho PATH
• /home/d/da/darin/bin/opt/local/bin/opt/local/bin
  /pbmutils/usr/bin/usr/sbin/opt/SUNWspro/bin/us
  r/ccs/bin/opt/local/X11/bin/usr/dt/bin/usr/open
  win/bin/opt/local/gnu/bin/opt/local/games/bin/u
  sr/ucb./
• If a program (like ls) is in one directory found
  in your path, then typing it (gtls ltentergt) will
  execute it.
• Otherwise you can type the full absolute address
  to execute a program (gt/usr/bin/ls ltentergt)

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finding things in your PATH.

• Type which ltcommandgt to find the location of
  the program which would be run when you type
  ltcommandgt.
• If you dont remember if it was chgrp or chgroup,
  type chltcontrol-dgt to get a list of commands
  that starts with ch.
• when all else fails, use find to find a file.
• gtfind ltstart dirgt -name .doc

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Other useful pre-defined shell variables

• HOST what computer youre logged into
• PAGER program used display man pages
• PWD current directory
• GROUP what group youre in
• USER your login

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Shell scripts.

• If you have a bunch of commands youd like to
  automate, you can put them on separate lines of a
  file. Then type source ltfilegt to run the
  script.
• If the first line of your script looks like
• !ltprogram namegt
• then you can make the script executable. When it
  executes, it uses ltprogram namegt to interpret the
  contents of the script.

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Login scripts

• Most people have a script that executes when they
  log in. It is commonly used to set up ones PATH
  and aliases.
• For Bash it is .bashrc file in your home
  directory

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vi

• is an editor available on all decent Unix
  systems. Developed at Berkeley.
• Has two modes command and insert. In insert
  mode you can type normally.
• Press escape to get into command mode. In
  command mode each letter is a command.
• hjkl ? ????

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vi commands

• h, moves cursor left
• j, moves cursor down
• k, moves cursor up
• l, moves cursor right
• x, delete character
• dw, delete word
• dd, delete line
• p, put last deletion after cursor
• u, undo last change

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vi commands (cont.)

• i, turn on insert mode (hit the esc key twice to
  stop)
• wq, write file and quit
• q!, quit without saving file
• ctrl f, move forward one page
• ctrl b, move backward one page
• /text, will search for next occurance of 'text'
  (hitting n will find next occurence)
• G, go to end of file
• 1G, go to first line of file

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STD

• All terminal programs have
• standard output, which is usually your screen
• standard input, which is usually your keyboard
• standard error, which is also the screen

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redirect output to a file with gt

• If you type who at the prompt, you will get a
  list of who is logged into the system.
• If you type who gtf, a file named f will be
  created and the standard output of who will be
  placed in that file instead of to your screen.

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gt vs. gtgt

• By default, who gtf will overwrite the file f.
• Use who gtgtf to append to f rather than
  overwriting it.

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redirecting input from a file with lt

• The program sort will sort its standard input and
  then print it on standard out.
• To sort the lines of file1 and display
• sort lt file1
• To sort the lines of file1 and save in file2
• sort lt file1 gt file2

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The output of one program can be the input to
another.

• who sort
• The output of who is sorted and shown on your
  terminal screen.

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grep

• grep shows only those lines containing its search
  pattern.
• To see all lines in a file containing bob
• grep bob lt file1

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The cat command

• the arguments to cat are concatenated together
  and displayed on stdout. To view a file
• cat file1
• if no arguments, cat puts on stdout whatever you
  type on stdin, so this does the same thing
• cat lt file1

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To start a process in the background, use .

• example
• big_program gt output
• big_program will not have input!

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Managing Jobs

• To suspend the currently active program, use
  ltcontrol-zgt.
• To return to the program you just suspended, type
  fg
• To put the program you just suspended in the
  background, type bg

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To see a list of your programs running, type ps.

• gtps
• PID TTY TIME CMD
• 866 pts/1 000000 tcsh
• 872 pts/1 000000 ps

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use kill to end a process

• gtps
• PID TTY TIME CMD
• 866 pts/1 000000 tcsh
• 874 pts/1 000000 cat
• 875 pts/1 000000 ps
• gtkill 874
• 1 Terminated cat

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kill -9

• If kill ltPIDgt doesnt end your process, use
  kill -9 ltPIDgt

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Other Unix Utilities

• Finding files
• find path name expression
• Ex. find -name ch
• Search home directory to find files that start
  with ch
• Displaying file contents
• cat filename
• more filename

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Other Unix Utilities

• Finding text file size
• wc filename
• Sorting (file contents) line by line
• sort filename
• sort lt filename
• Piping
• command command
• Ex. cat readme.txt sort

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Other Unix Utilities

• Translate or delete characters
• tr d 0-9 lt myfile.txt
• remove numbers from myfile.txt
• tr A-Z a-z lt myfile.txt
• convert upper case to lower case
• tr \n lt myfile.txt
• show contents word by word

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The End