Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
Chapter 9
Pipes, Filters, and Redirection
Chapter 9
Pipes, Filters, and Redirection
LECTURE NOTES
CHAPTER OUTLINE
Chapter Overview
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Will use redirection to redirect standard input
and standard output.
Learn how pipes can be used to connect
programs.
How filters can be used to manipulate data
will be explained.
What shell extensions are and how they may
be used will be discussed.
Learn how to combine commands using
pipes, filters, and redirection.
REDIRECTION OF STANDARD I/O
(INPUT/OUTPUT)
 Redirection of Standard I/O (Input/Output)
 What is keyed in is input.
 What is written to screen is output.
 Input/output called I/O.
 OS recognizes three standards:
 Standard input: Keyboard.
 Standard output: Screen.
 Standard error: place from which OS
writes error messages to the screen.
 Not all commands deal with standard
input and standard output.
 See PowerPoint slide #10 – Results of
Copy Command
 I/O redirection allows standard I/O to be
changed.
 Read from file, not keyboard.
 Write to printer, not screen.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
TEACHING SUGGESTIONS

Slides 2-6
 Chapter Overview duplicated in PowerPoint
slides.
 After completion of lecture, suggest to
students that they review Objectives and
Outcomes found on first page of chapter as
a check to see if they have mastered
concepts.
SECTION 9.1 (pp. 440-441)
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Slides 7-13
Discussion Question (1) - Explain redirection.
Discussion Question (2) - Explain the terms
standard input, standard output, and standard
error.
Discussion Question (3) - Does every operating
system command use standard input and
standard output? If not, why not?
Discussion Question (4) - What is the
difference between > and >> when redirecting
output?
Discussion Question (5) - Explain how the
symbol < is used.
Page 1
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems

Three redirection operators.
 The > redirects output of command to
device or file.
 The < asks for input from source
other than the keyboard.
 The >> redirects standard output and
appends but does not overwrite a file.
ACTIVITY—USING > TO REDIRECT
STANDARD OUTPUT
 Using > to Redirect Standard Output
 DATA disk in Drive A, A: \> displayed.
 Activity steps.
 Key in:
 DIR C:\WUGXP\*.TXT
 DIR C:\WUGXP\*.TXT >

Chapter 9
Pipes, Filters, and Redirection
TXTFILES.TXT
TYPE TXTFILES.TXT

Activity completed.
SECTION 9.2 (pp. 441-443)

 Redirection is either/or process - See on
screen, or prints to printer.
 Redirection can be used with commands
that writes its results to standard output
device (screen).
 Cannot use COPY DIR *.TXT - COPY
copies files, not commands.

ACTIVITY—USING < TO REDIRECT
STANDARD INPUT
 Using < to Redirect Standard Input
 DATA disk in Drive A, A: \> displayed.
 Activity steps.
 Key in:
 MD TEST
 COPY C:\WUGXP\*.NEW TEST
 DEL TEST\*.*
 N then DIR TEST
 TYPE Y.FIL
 DEL TEST\*.* < Y.FIL
 DIR TEST
 Activity completed.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Slide 14
Discussion Question (6) – Keying in COPY
DIR filename will not give you a file
containing the directory display. Why?
SECTION 9.3 (pp. 443-445)
 Slide 15
 DEL *.* needs keyboard response.
 Useful to lock up the system - i.e., write a
file with X <Enter>, then write command as
DEL \TEST\*.* < X.FIL. System will lock
up.
 Be careful with redirection of input.
- Tell OS to take input from a file; any
keyboard input will be ignored.
.
Page 2
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
ACTIVITY—USING >> TO ADD
REDIRECTED OUTPUT TO A FILE
 Using >> to Add Redirected Output to a File
 DATA disk in Drive A, A: \> displayed.
 Activity steps.
 Key in:
 COPY C:\WUGXP\*.TXT
 TYPE JUPITER.TXT
 TYPE MERCURY.TXT
 TYPE MERCURY.TXT >>
Chapter 9
Pipes, Filters, and Redirection
SECTION 9.4 (pp. 445-447)

Slide 16
 Can only use >>. There is no <<.
 >> between files – adds contents of first file
to end of second file.
 To append to end of existing file, use
double redirection symbol (>>)
JUPITER.TXT

 TYPE JUPITER.TXT
Activity completed.
FILTERS
 Filters
SECTION 9.5 (p. 447)
 Manipulate information.
 Slides 17-20
 Read information from keyboard.
 Change input in specified way.
 Compare filters to filters in water
purification system.
 Write results to the screen.
- Extract unwanted elements.
 Three OS filters - external commands.
- Send pure water on its way.
 SORT - arranges lines in ascending or
descending order.
 FIND - searches for particular group
Discussion Question (7) - What are filters?
of characters, called a character
string.
 MORE - temporarily halts screen
display after each screenful.
 OS creates temporary files while it
"filters" data.
 Important that there be access to the
disk and the filters.
 If a disk is write-protected, the OS
will not be able to execute filter
commands.

THE SORT COMMAND
 The SORT Command
 Sorts/arranges lines of text.
 Sends output to screen unless redirected.
 Default sorts in ascending order.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
SECTION 9.6 (p. 447)

Slides 21-22
 Sorts A to Z or from lowest to highest
Page 3
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems

SORT syntax: See PowerPoint slide #22.
 /R - reverses sort order- sorts Z to A,
9 to 0.
 /+n - sorts file according to characters
in column n.
 M kilobytes – amount of main
memory to use for sort
 /T – (Temporary) – path of directory
to hold sort’s working storage in case
does not fit into main memory.
 /O – Output – if not specified data
written to standard output.
Specifying output file faster than
redirecting standard output to same
file.
 [drive1:] [path1] filename1 - specifies
file (s) to be sorted.
 [drive2:] [path2] filename2 - specifies a
file where the sorted input is to be
stored.
ACTIVITY—USING SORT
 Using SORT
 DATA disk in Drive A, A: \> displayed.
 <F6> means to press the <F6> key.
 Activity steps.
 Key in the following commands.
Each command followed by <Enter>
 SORT then MECURY then VENUS
then EARTH then 3 then MARS
 JUPITER then < F6> then SORT
then 333 then 3 then 22 then 124
then <F6>
 Discuss results of this sort– sorting
by units not numerically.
 Key in the following commands.
Each command followed by <Enter>
 SORT then 333 <Spacebar>
<Spacebar > 3 then <Spacebar> 23
then 124 then <F6>
 Discuss result of this sort – using
spaces forces lines to be same
length – placing number digits in
proper position.
 Activity completed.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Chapter 9
Pipes, Filters, and Redirection
numbers (starting in first column).

Discussion Question (8) – What do the three
SORT parameters covered in this chapter—/n,
/O, and /R—represent?
SECTION 9.7 (pp. 448-450)

Slides 23-27
 <F6> same as pressing <Ctrl> + Z.
 Numbers can be character data –

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
- Phone numbers or zip codes.
Numbers - only when mathematical
operation is performed on them.
Character data sorted from left to right.
Numeric data sorted by units.
ASCII sort sequence:
- Punctuation marks (including spaces).
- Numbers.
- Letters (lowercase then uppercase).
Carolyn Smith before Robert Nesler because
SORT command looks at entire line and
Carolyn comes before Robert.
Left justify character data and right justify
numeric data.
Discussion Question (9) -Explain how the
SORT command works. Describe any
limitations of the SORT command.
Page 4
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
Chapter 9
Pipes, Filters, and Redirection
FILTERS AND REDIRECTION
 Filters and Redirection
SECTION 9.8 (p. 450)
 Standard output of filters is screen
display.
 Slide 28
 Can redirect both the output and the input
of the filter commands.
 Filter commands not usually used with
actual keyboard input.
 Filter commands used with input
redirected from a file, a device, or another
command.
ACTIVITY—USING THE SORT
COMMAND WITH REDIRECTION
 Using the SORT Command with Redirection
 DATA disk in Drive A, A: \> displayed.
 Activity steps.
 Key in:
 COPY C:\WUGXP\STATE.CAP
 SORT < STATE.CAP
 SORT STATE.CAP
 SORT /R < STATE.CAP
 SORT /+17 STATE.CAP
 SORT /+17 STATE.CAP >



SORTED.CAP
TYPE SORTED.CAP
SORT/ +17 STATE.CAP /O
BYCITY.CAP
TYPE SORTED.CAP
TYPE BYCITY.CAP


Activity completed.
SECTION 9.9 (pp. 450454)
 Slides 29-30
 /R – sorts in reverse or descending order.
 WXP – SORT does not require < prior to
file being sorted.
 /+n – sorts by column number .
Column – on screen is place occupied by
one character.
Column number really means character
number.
+17 – seventeenth position in list.
 /O – stores sorted data in a file (faster than
redirection).
 Till now, changed data not been saved to a
file. Now creating a new file.
 Break down SORT < STATE.CAP
- Can be written to screen (standard output)
- Therefore can be directed to file.

The FIND Filter

The FIND Filter.
 Searches for specific character string by
enclosing it in quotation marks.
 Command is looking for exact match,
therefore, is case sensitive unless use /I
parameter.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Discussion Question (10) -Identify one place
that standard output can be written.
SECTION 9.10 (p. 454)

Slides 31-34
 Example - Use TYPE command, FIND
command can tell if the word “indictment”
is in a file.
 Search option available in Start menu - can
search files for text.
Command line not as reliable in WXP
as it was in W2K
Page 5
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems

FIND syntax:
FIND [/V] [/C] [/N] [/I] "string" [[drive:]
[path] filename [ …]]



/V - displays all lines not containing
specified string
 /C - displays only the count of lines
containing a string.
 /N - displays line numbers with
displayed lines.
 /I - ignores the case of characters
when searching for the string.
 /OFF [LINE] - Do not skip files
with offline attribute set
 "string" - specifies the text string to
find.
 [drive:] [path] filename - specifies a
file or files to search.
If pathname is not specified, FIND
searches the text types at the prompt or
piped from another command.
FIND command at command line can
help find a file based on content.
ACTIVITY—USING THE FIND FILTER
 Using the FIND Filter
 DATA disk in Drive A, A: \> displayed.
 PERSONAL.FIL on DATA disk.
 Must use double quotes.
 Activity steps.
 Key in:


Chapter 9
Pipes, Filters, and Redirection
FIND "Smith" PERSONAL.FIL
 FIND /V "Smith" PERSONAL.FIL
 FND /N "Smith" PERSONAL.FIL
 FIND /C "Smith" PERSONAL.FIL
 FIND /I "Jones” PERSONAL.FIL
 FIND “Jones” PERSONAL.FIL /I\I
Activity completed.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1



Discussion Question (11) - What is the purpose
of the FIND command?
Discussion Question (12) - What are four
parameters that are used with the FIND
command and what do they represent?
Discussion Question (13) - Why must the
character string be enclosed in quotation marks
when using the FIND command?
SECTION 9.11 (pp. 454-457)

Slides 35-36
 Character string – enclosed in quotes
 FIND – case sensitive.
 Parameters.
/I – ignores case.
/V- search file for anything except what is in
quotes.
/N – finds specific line # of each
occurrence.
/C – numeric count of # of times specific
character string in file.
Page 6
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
PIPES
 Pipes
 Pipes - output from one program becomes
input to next program.
 Not limited to two programs.
 Pipes used with filter commands.
 Used to further refine data.
 Symbol is broken bar |
 Location of pipe not standard
 Filter commands.
 Commands read and write temporary
files to the disk.
 Filters are external commands.
 OS must be able to access the
commands.
 All files (even temporary ones) must be
named.
 Temporary files "hold" data until the
next command can process it.
 Temporary files are deleted when
pipes are done filtering.
 Filter commands will not work if a disk is
write-protected.
THE MORE FILTER

The MORE Filter
 MORE displays one screenful of data at a
time.
 Useful when want to read long text file.
 Pauses after screen is full.
- Press any key - next screen is
displayed.
 No more data in file – returns to system
prompt.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Chapter 9
Pipes, Filters, and Redirection
SECTION 9.12 (pp. 457-458)

Slides 37-41
 Term “pipe” refers to flow of info. from one
command to the next.
 Pipes move information the way water pipes
move water.
 Filter commands.
- Used with any command that uses
standard output or input.
- Transforms data to meet needs.


Discussion Question (14) - What are pipes?
Discussion Question (15) - Are there any
restrictions on the use of pipes? What are they?
SECTION 9.13 (pp. 458-459)

Slides 42-44
 MORE can be both redirected and used with
a pipe.
 Extended features
Pn
Display next n lines
Sn
Skip next n lines
F
Display next file
Q
Quit
=
Show line number
?
Show help line
<space> Display next page
<ret>
Display next line
Page 7
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems

MORE syntax: See PowerPoint slide #43.

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




Chapter 9
Pipes, Filters, and Redirection
[drive:] [path] filename - specifies file
(s) to display one screen at a time.
command-name - specifies a command
whose output will be displayed.
/E – enable extended features.
/C – clear screen before displaying page.
/P – expand FormFeed character.
/S – squeeze multiple blank lines into a
single line.
Tn – expand tabs to n space (default 8).
Switches can be present in MORE
environment.
+n – Start displaying the first file at line
n.
files – List of files to be displayed. Files
in the list are separated by blanks.

Discussion Question (16) - How is the MORE
command used?
If extended features are enabled –
following commands accepted at –
More—prompt
 See PowerPoint slide #44.
 Right column describes features
ACTIVITY—USING THE MORE FILTER
 Using the MORE Filter
 DATA disk in Drive A, A: \> displayed.
 Activity steps.
 Key in all bold commands.
 DIR | MORE then Return to System








Prompt
DIR | MORE then Return to System
Prompt
DIR | MORE then Return to System
Prompt
DIR | SORT / +39 | MORE then
Return to System Prompt
MORE PERSONAL.FIL then Return
to System Prompt
TYPE PERSONAL.FIL | MORE then
Return to System Prompt
MORE PERSONAL.FIL /C +20
MORE SORTED.CAP BYCITY.CAP
/C
Press <SPACEBAR>
SECTION 9.14 (pp. 459-466)

Slides 45-46
 By continuing to press <spacebar> will




return to system prompt.
With extended features, pressing Q will
break command and return to system
prompt.
Can connect several commands with pipes
and filters.
MORE can be used with any ASCII file.
/P parameter can only be used with DIR.
Demonstrate by using TYPE PERSONAL.FIL
/P.
 /P not a valid TYPE parameter.
 Records are lines of information in a data
file.
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Page 8
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
Chapter 9
Pipes, Filters, and Redirection
 MORE allows viewing file at a specified


line or record number.
MORE SORTED.CAP BYCITY.CAP
Press <SPACEBAR>


Close all open windows and
return to desktop environment
(GUI).
Activity completed.
OTHER FEATURES OF MORE
 Other Features of MORE
 If extended features are enabled – have
more choices available to you with
MORE command.

See PowerPoint slide # 45.



Command Prompt by default
enables shell extensions
 CMD /X - Enables shell
extensions
 CMD /Y -Disables shell
extensions.
Open Command Prompt window are
running a shell.
Shell is command interpreter used to pass
commands to operating system.
ACTIVITY—USING THE EXTENDED
FEATURES OF MORE
 Using the Extended Features of MORE
 DATA disk in Drive A, A: \> displayed.
 Activity steps.










Click Start/Run.
Key in: CMD.EXE /X
Click OK.
Key in: A: then MORE PERSONAL.FIL.
Press <Enter> twice then Q.
Key in: MORE PERSONAL.FIL
Key in: P then 5
Press <Enter> then = sign then S
Key in: 3 then press <Enter>
Close all open windows.

Activity completed.
 More filter can be used with more than one
file.
 /C parameter clears the screen before each
display.
SECTION 9.15 (pp. 466-467)

 Open Command Prompt window – running
a shell.
 Commands that use shell extensions: DEL,
COLOR, CD, MD, PROMPT, PUSHD,
POPD, SET, SETLOCAL, ENDLOCAL,
IF, FOR, CALL, SHIFT, GOTO, STARTS,
ASSOC, and FTYPE
 Command name with /? - full details on
what can be done with command.

Discussion Question (17) – What are two
useful features that extended features
provides for the MORE command?
SECTION 9.16 (pp. 467-471)

Slides 51-52
 Run remembers last command keyed in.
 /X – ensures that you are going to be able to




Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Slides 47-50
use extensions to commands.
With extensions enabled
Pressing <Spacebar>(referred to as
<Space> in syntax) - displays next page
Pressing <Enter>(referred to as <ret> in
syntax diagram) - displays next line in file
To exit MORE command key in Q (returned
to system prompt).
Press P where MORE stopped – can request
how many lines you want to display.
= sign – displays which line number you are
Page 9
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
Chapter 9
Pipes, Filters, and Redirection
on.
 S – asked how many lines you want to skip
in your display.
COMBINING COMMANDS WITH PIPES
AND FILTERS
 Combining Commands with Pipes and Filters
 Use pipes so standard output from one
command is standard input to next
command (filters).
 Use pipes to connect two or more
programs and create a flow of data.
 Redirecting output from a command is an
“instead of” process.
 When combine use of pipes and > redirection becomes end of pipeline.
 Last step in process.
ACTIVITY—COMBINING COMMANDS
 Combining Commands
 Open Command Prompt window.
 DATA disk in Drive A, A: \> displayed.
 Activity steps.
 Key in:
SECTION 9.17 (p. 471)

 When pipe symbol used – must be
command on both sides of symbol.
 Redirection used with “pipeline,” command does not have to be on either side
of > or >>
SECTION 9.18 (pp. 471-474)






DIR | SORT /+39 | MORE
Return to system prompt.
Key in:







Key in:



DIR | FIND “<DIR>“ SORT +39
Quotation marks around <DIR> so
command line would not use < and >
as redirection.


Activity completed.

Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Slides 56-57
 Data in PERSONAL.FIL not changed –

FIND "Teacher" PERSONAL.FIL |
FIND "CA"
 FIND "Teacher" PERSONAL.FIL |
FIND "CA" > TEACHER.FIL
 TYPE TEACHER.FIL
 FIND "PrOfeSSor" PERSONAL.FIL
| FIND "AZ" | SORT
Press up arrow once
Use left arrow key until cursor in under P
in PERSONAL.FIL
Key in /|<SpaceBar>
Press <End> key then <Enter>
Slides 53-55
searched data so display only those
lines/records that met your requirements.
Because FIND command sends output to
screen can redirect output.
Can use same filter more than once in same
command line.
Can use filters in combination in same
command line.
Pipe.
- Command on either side of pipe.
- Taking standard output of a command and
using it as standard input to next command.
Redirection.
- An “instead of” action.
- Only get one output place.
- Output goes to last place it is directed to
go.
Primary use of pipes and filters is to
manipulate the standard output and standard
input of commands.
Rarely use pipes and filters to sort or find
data in text or data files.
Page 10
Instructor: Prof. Michael P. Harris
ITSC 1405 – Intro to PC Operating Systems
Chapter 9
Pipes, Filters, and Redirection
Discussion Question (18) – How can
combining filters be useful?
Carolyn Z. Gillay, Bette A. Peat, Windows XP Command Line
Franklin, Beedle & Associates ©2003 ISBN: 1-887902-82-1
Page 11