UNIX

1
UNIX Linux Commands

• David Turton
• Conestoga College
• Institute of Technology Advanced Learning
• http//www.conestogac.on.ca/dturton
• Doon 1D17 x3610

2
UNIX history

• Ken Thompson ATT Bell labs
• 1969 - wrote UNIX on a PDP 7
• but PDP7 had a proprietary language
• wrote B, to be less platform-dependent
• Dennis Ritchie
• wrote C as true platform-indep. language
• rewrote UNIX in C, with Thompson

3
UNIX history (contd)

• Released to universities, mid 1970s
• free/cheap
• source code was made available
• Doctorates written improving efficiency
  security
• commercial systems were less flexible
• 4-year effect grads took UNIX to the world
• UNIX adopted by DOD, late 70s
• standards bodies intervene
• ANSI, IEEE, ISO, etc.

4
Appeal of UNIX

• Portable
• written in C (available for all platforms)
• I/O is device-independent
• multitasking/multiuser from onset
• network-ready built to share files
• many interface shells window managers
• blazingly fast, solidly reliable

5
UNIX Characteristics

• unfriendly
• terse
• treacherous
• unforgiving
• inconsistent
• non-mnemonic

typo
6
UNIX raison d'être

• UNIX assumes you know what youre doing
• Originally designed as a professional development
  environment
• by techies for techies
• verbose-averse
• warns of failure, not of success
• output of one process can be input to another

7
UNIX differs from DOS

• UNIX is case-sensitive, DOS isnt
• fred, Fred, FRED - are 3 different files
• UNIX doesnt warn of destruction
• UNIX views everything like a file off the root
  directory
• in DOS, a printer is different from a diskette
  (A) and the primary hard drive (C)

8
Where is UNIX used?

• Boeing cockpits
• airline reservations
• major government databases
• most Internet servers
• high-end CAD/design
• Jurassic Park
• Toy Story

• However
• It's being replaced by Linux
• The commands are the same

9
Multitasking gt 1 task active at a time

• To run multiple processes your must
• Trap interrupts
• i.e. file I/O, abends
• Timeslice
• tasks share available cycles
• O/S kernel, or core, owns all the hardware
• programs access devices via system calls to the
  kernel
• allows kernel to take control provides platform
  independence

10
Multiuser gt1 people sharing computer resources

• cant have multi-user w/out multitasking
• sharing data, programs, resources
• prime intent of UNIX
• not until Windows 3.11 (early 90s) could
  Microsofts OS share data
• optimizes investment
• increase use of resources lots of empty cycles
• necessary feature to support network servers
• a logon process is initiated (forked) as each
  terminal connects
• creates a process thread for user
• could fork again, if user multitasks

11
UNIX/Linux Command Syntax

• cp ri source destination
• cp (copy) command
• Lower case, no imbedded spaces
• Command line is space-delimited
• -ri options
• Dash denotes option(s)
• Multiple options can be combined (-ri)
• Or can be separate (-r -i)
• sequence doesn't matter
• Parameter for an option follows it
• Separated by a space (sort -kr -o param
  inputFile)
• Source
• Source files and/or directories, if any
• Destination
• Destination file/directory, if there is one, is
  at end

12
Standard Input, Standard Output, Standard Error
Output

• Standard input
• Defaults to the keyboard
• Ctrl d or D
• End-of-data
• Ctrl c or C
• Cancel command
• Standard output
• Defaults to the monitor
• Standard error output
• Defaults to the monitor
• Independent of standard output
• Can redirect any of these to/from somewhere else
  (later)

13
Sign-on, Navigating the File Structure

• David Turton
• Conestoga College, room 1B43
• dturton_at_conestogac.on.ca
• 748-5220 x8182

14
Logging in and out

• Login screen presented after power-up
• type your userid password
• passwords and userids are case sensitive
• Older systems typos can't be corrected
• Logging out
• type exit and press Enter
• startx
• Starts GUI interface from command interface
• Right-click on resulting window select "new
  terminal" to get a command-prompt window

15
passwd

• Command to change passwords
• follow the prompts
• confirm current
• enter new
• confirm new
• suggestions
• 6 characters long
• upper and lower case
• include numbers

16
wwho am i

• Used to find out who is on the system
• who am i
• shows your userid, terminal type, logon time
• w shows more information than who
• such as idle time, cpu load, current task, etc.

17
UNIX directory structure
18
Addressing

• Essentially the same concept as in DOS
• Working directory
• View path pwd (present working directory)
• Relative addressing
• Absolute addressing
• However
• Use "/" to separate directory/file names
• /home/tom/docs/resume
• There is no "drive letter"
• There's only one file system
• Everything is a file under the root

19
Directory Navigation

• pwd
• Print (display) the working directory path
• cd
• Change the working directory
• mkdir
• Make a directory
• rmdir
• Remove a directory
• ls
• List a directory's contents
• Refers to your home directory when used as part
  of a file's path
• cat more
• Used mainly to look at file contents

20
pwd
/

• Print the working directory
• absolute addressing (from the root)
• pwd
• /usr/tom

bin
usr
dev
carol
tom
You are here
21
cd path

• Change the working directory
• use either relative or absolute addressing
• with no arguments, sends you to your home
  directory

• pwd
• /usr/tom
• cd docs
• pwd
• /usr/tom/docs
• cd
• pwd
• /usr/tom

22
mkdir path

• Make a new directory
• use either relative or absolute addressing
• Note
• mkdir docs/team/status
• Creates directory status at end of given path
• Path (docs/team/) must already exist

• ls -F
• docs/ project.chart
• mkdir accounting
• ls -F
• accounting/ docs/ project.chart

23
rmdir directory

• Removes (deletes) a directory
• directory must be empty
• absolute or relative
• last directory in given path deleted

• ls
• accounting docs project.chart
• rmdir accounting
• ls
• docs project.chart
• rmdir /usr/home/tom/docs
• ls
• project.chart

24
ls options path

• List the contents of a directory
• Default working directory
• the path could be relative or absolute
• the path may specify a file-name pattern
• if path ends in a file name, will show
  information about the file

• options
• -l long descriptions
• -a all (incl. hidden)
• -F indicate file-type
• -r reverse order
• -d directory info only
• (not its contents)
• -R recursive
• (directory all subdirectories)

25
ls examples

• ls
• docs project.chart
• ls -a
• .profile docs project.chart
• ls -al or ls -a -l
• -rw-r--r-- 1 tom grp1 1036 Sep 12 1102 .profile
• drwxr-x--- 1 tom eng 512 Sep 13 0935 docs
• -rw-rw-r-- 1 tom grp1 4096 Sep 23 1002
  project.chart

Hidden file
26
cat options file-list

• concatenates files together
• two files, each of 3 lines, concat to 6 lines
• writes to the standard output device
• Commonly used just to list file contents
• if no file name provided
• reads from the standard input device
• terminated by D (end-of-data)

27
more options file-list

• Used for long files
• uses standard output device like 'cat'
• but only displays a page at a time
• at the bottom of the screen, shows
• --More--(37)
• meaning 37 of the file has been displayed
• can enter prompts here, like h (help), b
  (back), space (forward a page), enter (forward a
  line), etc.
• ie keystrokes are commands
• 'q' to quit

28
A shortcut to creating files using gt

• gt redirects standard output to a file
• cat gt fileX
• accepts data from the standard input device
• (no input file-name given)
• Standard output is redirected to fileX
• fileX is created, empty, before the command
  executes
• If fileX exists before command is run
• It will be deleted recreated empty.
• redirection/pipes/filters are covered later

29
man -k command UNIX help or manual pages

• To get help on a command like ls, type
• man ls
• Will show
• Command syntax,
• Options,
• Examples

• If dont know command, use keyword search
• man k list
• Will show all commands with list coded as a
  keyword

30
Moving/copying/deleting/finding files

• David Turton
• Conestoga College - 1B43, x8182
• dturton_at_conestogac.on.ca

31
File Manipulation

• cp
• copy file
• mv
• move file (copy remove)
• rm
• remove (delete) file
• touch
• update last used date
• create file if doesn't exist

32
copycp options source source-list destination

• if destination is a directory, copies the source
  file(s) to that directory
• otherwise, creates a copy with given name
• if the file already existed, its now gone
• options
• i interactive warn of override
• r recursive copy source dir contents
  sub-dirs
• can use . to denote working dir
• cp /usr/tom/status.txt .
• Note destination must be specified

33
movemv options source source-list destination

• Move or rename a file
• current name to new name
• existing file(s) to an existing dir
• existing dir to new dir
• options
• -f force - dont warn of permissions
• -I interactive - warn of overriding a file

34
Remove/Deleterm options file-list

• Removes/deletes a link to a file
• Normally won't delete a directory (see r)
• need execute write permission to directory
• options
• -f - force
• -i - interactive (ask if really want to)
• -r - recursive directory its contents

35
touch option file-list

• Update a files modification time
• creates file if doesnt exist
• option
• -c don't create file(s)

36
find path options

• Finds names of files and directories that meet
  given criteria
• including those in subdirectories
• displays in absolute format
• ls /mydir find /mydir -print
• myfile.txt subdir tmp /mydir
• /mydir/myfile.txt
• /mydir/subdir
• /mydir/subdir/anotherfile
• /mydir/tmp
• etc

37
Options for find

• -print
• use std output
• usually not required
• -type d
• directory names only
• -type f
• file names only
• note syntax
• -option whitespace parameter

• -ctime 3
• files changed 3 days ago
• -ctime -3
• files changed within last 3 days
• -atime 3
• files accessed more than 3 days ago
• -newer fred
• display files that have been changed after the
  given file

38
File-name searches

• -name pattern
• Files/directories matching the given pattern
• Pattern usually contains glob (wild card)
  constructs
• example
• find . -name ?onnet

• Note quotes
• the pattern is quoted so the shell does not
  resolve it first
• find . -name ?onnet
• becomes
• find . -name sonnet bonnet
• which gives a syntax error

39
find negating options with !"!" also known
as a "bang", "blast" or "not"

• Use ! as in
• find . ! -name ?onnet all files that dont
  match pattern
• find . ! -ctime -365 changed more than a year
  ago
• find . ! -newer sonnet files/dir not newer than
  sonnet
• note you can combine options, as in
• find /mydir -type f -newer ./sonnet
• Find just files that are newer than sonnet
• exercise does ! negate everything or just the
  next option?

40
Redirection, sort wildcards

• David Turton
• Conestoga College - 1B43, x8182
• dturton_at_conestogac.on.ca

41
Redirection Operators

• Redirect std output to file gt gtgt
• redirect std error output 2gt 2gtgt
• redirect std input from file lt
• pipe std out to std in
• tee pipe - file - pipe tee

42
Redirecting Standard i/o

• Most utilities are not specifically designed to
  work together
• most use standard input standard output
• the shell allows you to piece utilities together
• whosort gt user.list
• "list everyone on the system, sort results by
  userid store in file user.list "

43
Redirection gt gtgt lt

• Redirect std output to a file
• cat gt new.file 2gtbad.msg
• new.file is deleted recreated
• any error messages go to file bad.msg
• cat gtgt file2
• append std output to file2 (current data
  unaffected)
• Redirect std input to come from a file
• mail fred lt broadcast.mail
• have mail take its input from file, not keyboard

44
Pipe

• reconnect std output of one command to std input
  to another command
• same as two redirection commands but without an
  intervening file
• whosort
• same as
• who gt temp.file
• sort lt temp.file
• rm temp.file

45
Pipe vs. redirection hints

• View the redirection symbol as a funnel going to
  or coming from a container or file
• gt gtgt lt
• view a pipe as a pipeline between two continuous
  processes
• ls -lR more
• remember UNIX command-lines must start with a
  command and flow left to right
• you cant lead with an input file name
• the shell acts on the redirection before
  executing the command
• the command doesnt know about it or see it

46
sort options sort-keys file-list

• sort one (or more) files
• if no files, uses std input (sorts from start of
  line to end of line)
• if no -o option, uses std output
• options
• -d dictionary ignore punctuation
• -f force to lowercase
• -n numeric honour decimal, minus
• -tc fields separated by character c (default
  blank or tab)
• -o filename output file

47
sort keys -k m.noptions

• m sort field
• .n (optional) character from start of sort field
• Options (applied to this key)
• d dictionary order (ignore punctuation)
• f sort as if all lowercase letters
• M sort by month name
• n sort as a number
• r reverse order
• Assume the following data
• -rw-r--r-- 1 dturton wheel 29 Apr 17 1707
  people
• sort -k 9f means
• sort by file-name (people), force to use lower
  case

48
grep options string file-list

• Returns all lines with the given string
• From contents of given files
• Std input used if no filenames given
• Great for data piped from another command
• options (some)
• -c just count records that meet criteria
  
• -i ignore case
• ls -l grep fred
• display records from directory listing that have
  fred in them

49
UNIX naming conventions

• Up to 255 characters long
• any character but /
• recommend only use
• A-Z
• a-z
• 0-9
• . _ - (- not as 1st character)
• otherwise the shell may misinterpret
• i.e. variable names -r, togtfrom

50
Wildcard or glob constructs

• - zero or more, any character
• ? - 1 only 1, any character
• 125-9 - 1 only 1 of given characters
• ! - not version of above
• \ - do not resolve wildcard(s)
• Used for file-name "patterns"
• Shell will resolve before command executes

51
? Single any-char substitution

• means 1 and only 1 character
• can be interpreted as any character
• ls
• memo memo1 memo10 memo2
• echo memo?
• memo1 memo2
• memo 10 has 2 characters after memo
• memo has 0 characters after memo

52
Multiple character substitution

• means 0 or more characters
• can be any character (or none)
• ls
• memo memo1 memo10 memo2
• echo memo
• memo memo1 memo10 memo2
• echo memo1
• memo1 memo10
• echo memo3
• memo3 note no files, passed as a string

53
single specific substitution

• means 1 and only 1 character
• matching only characters between braces
• can use ranges, such as a-f
• memo123 memo1 memo2 memo3
• memo1-35 memo1 memo2 memo3 memo5
• memo1-35 memo15 memo25 memo35

54
Wild Card Interpretation

• Shell interpolates file name(s) from the working
  (or given) directory
• passes file names found to command
• if none found, passes string as given
• ls
• memo memo1 memo10 memo2
• ls memo?
• memo1 memo2
• touch memo3?
• ls
• memo memo1 memo10 memo2 memo3?

55
Quoting

• override the shells interpretation of a
  character
• to exempt a single character
• precede with \
• grep \gt means look for gt sign inside the file
• to exempt one or more characters
• put between a pair of quotes (single or double)
• grep gt
• cp normal.var my long variable name

56
Echo

• echoes everything on the command line
• outputs to standard output device
• good debug for wildcards
• good for building a file line-by-line using gtgt
• echo this is a free sentence
• this is a free sentence
• ls
• memo memo1 memo10 memo2
• echo memo?
• memo1 memo2 lt--------shell interpreted before
  command was executed

57
Editors vi or Pico
58
UNIX Regular Expressions

• Patterns for data, not file names

59
grep options string file-listusing regular
expressions on data

• who grep 'cpa'
• Return lines that contain "cpa"
• who grep "cpa"
• return lines that start with cpa

60
Wildcards or glob constructs

• Examples
• zero or more, any character
• ? 1 and only 1, any character
• 1 and only 1 of the given characters
• ! 1 and only 1, not of the given characters

• Used to generate a list of file names
• I.e. not used when working with file content

61
Regular Expressions

• Following match 1 character
• start of line
• end of line
• 1 of given chars
• . 1 of any char
• \d 1 number, like 0-9

• used when searching file content
• not interpreted the same as wildcards used in
  file names
• quote regular expressions
• Else shell will interpret as file-name patten

62
Special consideration . and

• How do you search for a period?
• Use \ to override a special interpretation
• grep \. nursery
• all lines that end with a period

• How do you say not one of these characters?
• Use within braces
• grep a-zhe nursery
• matches She, The, but not she or the

63
Regular Expression Modifiers

• For example
• (http//)?
• http// is optional, occurring once, if at all
• a
• At least 1 a, but there may be more
• a-z1,3
• At least 1, and no more than 3, lower-case
  letters
• (webftp)? server
• web server, ftp server or server at
  start-of-line
• NAL.c
• NAL followed by zero or more of any char, then
  c

• Apply to preceding expression or character
• zero or more
• ? zero or one
• one or more
• n,m n to m times
• Can act on
• Single character
• constructs
• ( ) constructs
• Special chars, like .

64
Where else are regular expressions used?

• Anything looking at data
• search-and-replace in vi
• searching in more
• tr, sed, awk, etc.
• Netscape Proxy Server
• JavaScript

65
File Permissions

• David Turton
• Conestoga College - 1B43 x8182
• dturton_at_conestogac.on.ca

66
File Access Restrictions

• Unix was designed to share data programs
• but not everythings for everyone
• limit HR/payroll access
• control production code changes
• 3 independent permission classifications
• the owner/creator
• the group the owner belongs to
• everyone else

67
File Permission

• Viewed via ls -l
• drwxr-xr-x 1 dturton group1 2984 May 5 1005
  sub-dir
• -rw-rw-r-- 1 dturton group1 256 May 7 1100
  file-a
• owner owners group
• (r--)others
• (rw-) owners group
• (rw-) owner
• - file, d directory, l symbolic link
  

68
Directories are people too!

• A directory is a file
• which contains info pointers to other files
• whose permissions say what you can do to it and
  its contents
• you execute a directory to display its contents
  intelligently
• you write to a dir. to add or delete a file

69
File vs Directories

• Files
• r - read
• w - write (modify contents)
• x - execute
• Directory
• r - read(list) directory contents
• w - write to directory(add/del files sub-dirs)
• x - required with read

70
chmod -R ugoa-rwx file-list

• To change file permissions
• -R recursive apply to all subsequent files/dir
• ugoa user/owner, group, others, all three
• - add(), remove(-), or set only() the
  following permissions
• rwx read, write, execute
• chmod go-r my.file
• remove read permission to my.file for my group
  and others

71
chmod 777 file-list(absolute version)

• 777- 1 digit each for owner, group, others
• 4 - read sum, to get a
• 2 - write single-digit
• 1 - execute permission setting
• examples
• 644 - owner(read/write), groupothers(read only)
• 755 - owner(read/write/exec), groupothers(read/ex
  ec)