INTRODUCTION TO UNIX

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INTRODUCTION TO UNIX

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Title: INTRODUCTION TO UNIX

1
INTRODUCTION TO UNIX

INTRODUCTION TO THE UNIX OPERATING SYSTEM
SESSION 3

2
BASIC EDITING WITH VI AND EMACS
3
Learning to Use the Text Editors

UNIX systems generally provide three text editors
as standard parts of the operating system release
vi, the visual editor
ed, a line oriented editor
sed, a stream oriented editor

4
Text editing tools in UNIX

Designed for a terse, very fast user interface
and operation that favors the skilled expert
emacs, which is not provided as standard, is
slightly easier to learn and work with
vi, the standard full-page editor, should be
learned since it can be found on any system

5
The vi Text Editor
6
Setting your terminal type

vi is terminal-independent so it can be used on
any terminal type
to let vi know what type of terminal is being
used, the TERM environment variable must be set
properly
TERMansi
export TERM

7
Setting your terminal type

the TERM variable is generally set when the user
logs in by the .profile shell script
vi uses the TERM entry to locate the correct
control sequences to send to the terminal by
looking at the terminfo data base,
usr/share/lib/terminfo or /etc/termcap on older
releases of UNIX

8
Setting your terminal type

80386/80486 based UNIX systems use TERMAT386 (or
TERMat386) for their system console
X window systems generally use TERMxterm for
proper operation

9
Starting the vi editor

vi can be started from the shell in the following
fashions
vi old.file
vi new.file
vi file1 file2
vi

10
Starting the vi editor

vi may also be opened to any specific line number
of an existing file or with any vi command to be
interpreted through the use of the "" option
vi 45 old.file
vi old.file
vi /textstring old.file
the screen cursor marks the place of the current
line and current position

11
Modes in vi

vi has three modes of operation
command mode
input or text mode
last line mode

12
Modes in vi

the option "showmode" may be turned on to display
the current mode on the screen so that input
errors are less likely
set showmode

13
Switching modes

last line mode may be activated from command mode
by entering "" and when the command entered is
completed vi returns to command mode
command mode may be activated from text or input
mode by pressing the ESCAPE key

14
Switching modes

text or input mode may be entered from command
mode through a variety of commands

15
Ending your vi session

to exit from vi, the command "q" may be entered
while in last line mode current changes to the
file may be abandoned by using the "!" (bang)
after the exit command "q!"

16
Writing files

files are written from the vi buffer to the disk
by the "w" command
new files may be named and existing files may be
saved under another name by using the write
command as follows "w newfile

17
Writing files

the write and quit commands may be combined to
save a file and exit the editor in one operation
as follows "wq"
The command "ZZ" may be used to write a file and
quit the editor when in command mode

18
Reading files

the "r" command may be used in last line mode to
read a existing file into an empty buffer or to
add the contents of the file to the existing
buffer
line numbers may be added to the command to read
in the desired portions of the file to the buffer

19
Changing files

the "n" command closes the current file and
loads the next file in the vi command argument
list to the edit buffer
only one file at a time may be edited and the
current file is closed when the next file is
loaded all changes must be saved or abandoned at
that point

20
Redrawing the screen

the CTRL-L operator may be used to force vi to
redisplay the current screen in the event that it
becomes corrupted

21
Escaping to the shell

the "!" operator may be used in last line mode to
execute a command in a subshell
!ls
!sh

22
Escaping to the shell

while the command is executing, vi is temporarily
suspended but it will resume following the
command
a subshell may be executed and all UNIX
operations can be done while vi waits to resume

23
Configuring vi options

the vi editor has many options that can be used
to change its behavior and make it a bit easier
to use

24
Configuring vi options

the "set" command can be used to temporarily set
options within a current vi session
set all (shows all available options)
set showmode
set noshowmode ("no" turns off option)
set window10
set number (displays line numbers)

25
Configuring vi options

the environment variable EXINIT may be used in
the .profile shell script to provide the "set"
commands to vi when it starts up
EXINIT'set number showmode' export EXINIT

26
Editing in vi

Undoing a change
the "u" operator may be used in command mode to
undo the last change made to the file
only the most recent change is saved by the editor

27
Entering input mode from command mode

The following operator may be used from command
mode to switch to text or input mode
i enter text before cursor
a enter text after cursor
I enter text at start of line
A enter text at end of line
o open line above and enter text
O open line below and enter text

28
Command mode

command mode is entered from text mode by
pressing the ESCAPE key

29
Moving around in the buffer

the following operators may be used to move
around the text buffer while in command mode
l move one space right
L move to the last line on the screen
h move one space left
H move to the top line of the screen

30
Moving around in the buffer

the following operators may be used to move
around the text buffer while in command mode
j move one line down
k move one line up
move to the end of the line
move to the start of the line

31
Moving around in the buffer

the following operators may be used to move
around the text buffer while in command mode
b jumps to beginning of previous word
w jump to the next word
e jump to the end of word
G jump to the end of the buffer

32
Moving around in the buffer

the following operators may be used to move
around the text buffer while in command mode
CTRL-d scroll forward
CTRL-u scroll backward
CTRL-f next screen
CTRL-b previous screen

33
Searching for text

a variant of last line mode allows you to search
for text strings in a file being edited
enter a '/' for a forward search or a '?' for a
backward search and the text string for the
search
/search.string

34
Changing text

the commands 'r', 'R', 'C', and 'J' are used to
change existing text
'r' replaces a single character leaving you in
command mode
'R' lets you replace as many characters as you
wish starting at the current cursor position,
leaving you in input mode

35
Changing text

the commands 'r', 'R', 'C', and 'J' are used to
change existing text
'C' lets you change the whole line
'J' merges two lines of text by deleting the
newline character at the end of the current line

36
Deleting text

vi provides a number of operators for deleting
text
The 'x' operator deletes the current character
the 'dd' operator deletes the current line the
'dw' operator deletes the current word the 'cw'
operator is used to change the current word the
'cc' operator changes the current line the 'D'
operator deletes from the cursor position to the
end of the line

37
Deleting text

vi provides a number of operators for deleting
text
numbers of lines and ranges of numbers may be
used with all of these commands
3,5d
6dd
5dw

38
Repeating a change

The '.' dot command applies the last change to
the current cursor position
This includes text addition and deletion
operations as well as replacements

39
Cut and paste operations

Blocks of text may be pulled out of a file into a
buffer and then replaced into the where desired
the 'Y' command yanks text lines out of the file
and the 'p' command places them back into the
file after the current line the 'P' command
places them back just above the current line

40
Cut and paste operations

text deleted with commands like 'dd' may be
replaced at the current cursor position using 'p'
or 'P'
the 'u' command replaces text at the position it
was taken from (undo)

41
Cut and paste operations

buffers may be named with a single letter to
store multiple text strings
7"aY
and replaced with
"ap

42
Cut and paste using line numbers

Last line mode provides commands to move and copy
blocks of lines by number using the 'm' operator
for move and the 't' operator for copy
3,5m9
3,5t9
6t9

43
The emacs Editor
44
The emacs editor

Is not part of the standard release of the UNIX
system although many sites make it available to
their users
very different than vi
always in input mode
CTRL key oriented commands
ESC key commands (meta commands)

45
Using Editors with the X Window System
46
vi and emacs

are not designed to take full advantage of the X
Windows system
the editor may be used in this environment but
the scrolling features of the X Windows will not
affect text within the editors
care must be taken to set options in the editors
to work with the xterm settings

47
REGULAR EXPRESSIONS AND ADVANCED EDITING
48
Regular expressions

A regular expression consists of operators that
describe single characters to search for
anywhere a /string/ is used, a regular expression
may be substituted

49
Regular expressions use the following operators
and syntax

the '.' operator substitutes for any single
character and may be used in combination with
other characters
a.c
a..
..c

50
Regular expressions

the and brackets may be used to define the
set of characters that will match any single
character
abc
aA
aAbB
0123456789

51
Regular expressions

the and brackets may be used to define the
set of characters that will match any single
character
0-9
A-Za-z
s/aAbB/new string/g
1,s/0-9/new string

52
Regular expressions

special characters such as the may be
represented in a regular expression by preceding
them with a \ (backslash) character

53
Regular expressions

two, three, or more regular expressions may be
combined and the '' operator may be used to
indicate zero or more occurrences of the
preceding single character expression
s/0-90-9/new string
s/./new line
s/0-90-9/new string/g

54
Regular expressions

the use of the '' operator allows you to add a
string to an existing string of characters
instead of deleting thee existing string
s/0-90-9/add string
s/a-zA-Za-zA-Zadd string/g

55
The 'grep' Command
56
The 'grep' (global regular expression and print)
command

Is a filter which reads std. input or a list of
files given as arguments and writes to std.
output, any lines containing the match string
using the 'grep' command
grep match.string textfile
cat textfile grep "a-z12
cat file1 grep "a-z" gt errorfile

57
The 'grep' Command

options for the 'grep' command
'-v' select non matching lines
'-c' count matching lines
'-n' list line numbers with match string
'-i' ignore case distinctions

58
The 'grep' Command

the 'egrep' (extended) and 'fgrep' (fixed)
commands provide search capabilities optimized
for different circumstances
the 'fgrep' command only accepts a fixed string
to search for

59
The 'grep' Command

the 'egrep' command provides more regular
expression operators for more complex match
expressions
'' zero or more occurrences
'' zero or more occurrences
'?' zero or one occurrence
'' either of a pair expressions
'()' use of parenthesis for grouping
'-f file.name' match expression in file

60
The 'sed' Stream Editor
61
The 'sed' (stream editor)

Combines characteristics of both 'ed' and 'grep'
allowing changes to be made in the input file it
is often used with large files which can not be
handled easily by an interactive editor

62
The 'sed' (stream editor)

using the 'sed' command
sed "s/hello/goodbye/" textfile
sed "/hello/d" textfile
sed "s/hello//" textfile
sed "3,7s/hello//" textfile
sed "/hello/,/goodbye/s/bad/good/g file
sed -f commandfile textfile gt outfile

63
Basic Editing with 'ed

The 'ed' command, a line-oriented editor which
serves as the basis for all the other editors
under UNIX

64
Using the 'ed' command for line-oriented text
editing operations

entering 'ed
ed filename
260
ed newfile
?newfile
ed

65
Modes in 'ed

'command mode' is used to enter commands to 'ed'
such as writing a file or searching for text
strings you are in this mode when you enter 'ed
'input mode' is used to enter text into your file

66
Turning on prompts and help

the 'P' operator will turn on an '' prompt when
you are in command mode
ed filename
260
P

67
Turning on prompts and help

the 'H' operator will display a more informative
error message when selected
ed filename
260
P
H
l
line out of range

68
Write and quit

the 'w' operator writes the file you are editing
from the ed buffer to a file, prompting with a
'?' if no file has been named
ed filename
260
P
w
260

69
Write and quit

the 'q' operator allows you to quit the editor if
no changes have been made in the file since the
last save if changes have been made, you will be
prompted for confirmation
ed filename
260
q

70
Working with lines

in command mode the following apply
'.' current line
'' last line
'p' print current line
ed textfile
260
p
last line of file

71
Working with lines

the '' operator tells you the line number when
used with '.' or '' and line numbers may be used
in command mode to indicate positions for
operator actions
ed sixline
260
p
line six text

72
Working with lines

.
6
6
1,2p
line one text
line two text
3,p

73
Working with lines

line three text
line four text
line five text
line six text
-1,p
line five text
line six text

74
Working with lines

,p
line one text
line two text
line three text
line four text
line five text
line six text

75
Working with lines

4
line four text
p
line four text
q

76
Input mode

the 'a' (append, after current line) and the 'i'
(input, before current line) operators are used
to go into input mode, text may then be typed
into the file
you remain in input mode until using the '.'
operator on an empty line which returns you to
command mode

77
Input mode

the 'a' and 'i' operators may be preceded by a
line number to begin text entry at a specific
place in a file
ed text
?text
a
line one

78
Input mode

line two
line three
.
,p
line one
line two

79
Input mode

line three
w
q

80
Deleting lines

the 'd' operator will delete the current line
from the text file it will also accept a line
number or range for deletion
ed text
,p
line one
line two
line three

81
Deleting lines

2
line two
d
,p
line one

82
Deleting lines

line three
w
q

83
Undoing mistakes

the 'u' (undo) operator allows you to undo the
last change made to the file and restores the
buffer to its previous state
using the 'u' operator a second time restores the
buffer to the state it was prior to the first
'u' operator

84
Searching for strings

the '/' operator instructs 'ed' to search for a
string, starting at the current line and
continuing around from the beginning of the file
until the current line is reached again a
backwards search may be done using the '?'
operator
a search may be repeated by simply entering a '/'
or '?' followed by a return or enter

85
Substituting sections of text

strings may be replaced within a file using the
's' (substitute) operator followed by a '/', the
text string to replace, a '/', and the
replacement string
the 's' operator may use line numbers or ranges
for its operations otherwise, only the current
line is processed

86
Substituting sections of text

the '' operator is used to indicate the
beginning of a line and the '' operator is used
to indicate the end of a line for the purposes of
preceding or appending text to a line
ed text
,p
text one

87
Substituting sections of text

text three
1,s/text/line
line three
,p
line one
line three

88
Substituting sections of text

1,/line //
,p
one
three
s//this is line
this is line three

89
Substituting sections of text

1s// is enough lines
one is enough lines
,p
one is enough lines
this is line three
w
q

90
Making global changes

the 'g' (global) operator may be used following
the replacement string (closed by another '/') to
indicate that all occurrences of the target on a
line are to be replaced

91
Making global changes

a "context address" may be substituted for the
target range of this operator or any of the 'ed'
operators providing extremely powerful
capabilities
1,s/old/new/g
/start/,/end/s/old/new/g

92
Moving and copying lines

the 'm' command (move) allows you to move a line
or range of lines from one place to another in a
file

93
The 't' command (copy)

allows you to copy a line or range of lines from
one place to another in a file
.m
3,5m1
2,4t

94
Reading in another file

you may read another file into the edit buffer
with the 'r' (read) operator this will insert
the file after the current line unless a line
number is user with the operator
r oldfile
0r oldfile
23r oldfile

95
Shell escapes, the '!' operator

the '!' operator allows you to execute any shell
command from within 'ed' including a subshell if
needed the subshell may be terminated with the
CTRL-D sequence and you will be returned to the
editor
!cat textfile
!sh

96
MORE USEFUL GENERAL PURPOSE COMMANDS
97
The Environment Revisited

Exporting environmental variables to subprograms
and shells
the 'export' command
export
export LOGNAME
export PATH
export TZ
export TERM

98
The 'PATH' variable

echo PATH
/usr/hal/bin/bin/usr/bin/usr/ldbin
PATH/etc/usr/bin
export PATH

99
The 'banner' Command

The 'banner' command blows up its arguments to
large size and writes them to standard output
using 'banner
banner HELLO
banner "job 1
banner job 1

100
The 'clear' Command

The 'clear' command erases the screen and
displays the '' prompt on the top line
using 'clear
clear

101
The 'date' Command

The 'date' command displays the current date and
time stored on the system
using the 'date' command
date
Wed Jan 18 183000 PST 1989

102
The 'cal' Command

The 'cal' command produces a calendar of the
current month on its standard output
using the 'cal' command
cal
cal 1948
cal 4 1948

103
The 'calendar' Command

The 'calendar' command provides a basic reminder
service taking input from a file named "calendar"
and searching it whenever the command 'calendar'
is entered
The command provides as its standard output, a
listing of the lines in the file which match
today's or tomorrow's date

104
Using the 'calendar' command

calendar
appointment 1
appointment 2

105
The 'more', 'pg', 'head', and 'tail' Commands
106
The 'more' command

allows you to display a file on the screen and
move forwards and backwards through it
to advance through the screens of text, press the
SPACEBAR or 'F' CTRL-B move backwards through
the text CTRL-L redisplays the current screen

107
The 'more' command

the command will also accept regular expressions
for text searches using 'ed' syntax
'more' will look at multiple files and skip
forwards and backwards through the list using n
(next) and p (previous)
more file1 file2 file3

108
The 'pg' (page) Command

allows you to display a file on the screen in
similar fashion to 'more
The command also allows you to move around in the
file or the list of files using operators as in
'ed' and regular expressions as in 'grep

109
The 'pg' (page) Command

using the 'pg' command operators at the ''
prompt at the bottom of the screen
h help
q or Q quit
ltblankgt or \n next page
l next line
d or D display half page more
. or L redisplay current page

110
The 'pg' (page) Command

f skip next page forward
n next file
p previous file
last page
w or z set window size display next page
s savefile save current file in savefile

111
The 'pg' (page) Command

/pattern/ search forward for pattern
?pattern? search backward for pattern
pattern search backward for pattern
!command execute command

112
Using the 'pg' command

pg textfile1 textfile2
cat file1 file2 pg

113
The 'tail' Command

looks at the end of the file given as an argument
and writes the last 10 lines of the file to
standard output
using the 'tail' command and its options
tail /etc/inittab
tail -6 /etc/inittab
tail -100c /etc/inittab
tail -f growing.file

114
The 'cmp' command

The 'cmp' (compare) command will compare any two
files, text or binary, and either list the byte
number of the first difference encountered or
list the byte number and values for each
difference in the files

115
Using the 'cmp' command

cmp file1 file2
cmp -l file1 file2
cat file1 cmp -l - file2

116
The diff' command

The 'diff' (differences) command is used for text
files only and produces an index of all lines
that differ between two files, along with their
line numbers and what changes are required to
make the files the same
options for 'diff' include the '-b', ignore
blanks, and the '-e', produce 'ed' script to make
the files the same

117
Using the 'diff' command

diff file1 file2
cat file3 diff -b - file2
diff -e file1 file2 gt ed.script
(cat ed.script echo w) ed file1

118
The 'dircmp' command

The 'dircmp' command compare the contents of two
directory subtrees, reports on files that appear
in one directory only, and compares the files
(using 'cmp') that appear in both directories

119
The 'dircmp' command

it may also be used with the '-d' option to
report the differences
using the 'dircmp' command
dircmp HOME /tmp/copied

120
The 'sort' command

The 'sort' command is a filter which reorders a
stream of text files into alphabetical order
using the standard ASCII collating sequence,
taking a list of filenames as arguments or
reading standard input it writes the sorted
lines to standard output

121
Options for the 'sort' command include

'-m' merge
'-n' numeric order
'-f' ignore uppercase/lowercase differences
'-d' dictionary, ignore punct. Characters
'-M' sort on first three characters as a month
field (Jan, Feb, etc.)

122
Options for the 'sort' command include

'n' select sort key field (delimited by spaces)
by skipping to the next field after the number
'-n' stop sorting on the field just before the
number
'-t' select a different delimiter, ie. -t or
-t
'-b' ignore the "blank" character
'-r' sort in reverse order

123
Using the 'sort' command

sort datafile
sort -n datafile
sort -f textfile
sort 1 textfile
sort 3 -4 0 -1 datafile
sort -t specialfile

124
The uniq' Command

The 'uniq' (unique) command is used to produce a
count of occurrences of a specified line or field
in a file using a sorted file as input and writes
to standard output

125
Options for the 'unique' command

no options - writes one instance of every line
that is different then other lines
-u produces only lines that are not repeated in
the input

126
Options for the 'unique' command

-c count the number of occurrences of the unique
lines in the file
-d produces only lines that are duplicated in
the output
-n ignore the first 'n' fields in its comparison
n ignore the first 'n' characters of the line

127
The 'sort' and 'uniq' Commands

using the 'uniq' command
sort datafile uniq
sort datafile uniq -c

128
The 'cut and 'paste' Commands

The 'cut' command is used to copy only some
fields of an input line to the output while the
'paste' command takes two or more files as input
and reads a line from each file, combines them
into one line using right to left order with a
tab character between the fields, and writes them
to standard output

129
Using the cut' command

cut -b list -n file ...
cut -c list file ...
cut -f list -d delim -s file ...

130
Using the cut' command

A mapping of user IDs to names follows
cut -d -f1,5 /etc/passwd
cut -d -f1,5 /etc/passwd
To set name to current login name
namewho am i cut -f1 -d' '

131
Using the 'paste' command

paste file1 file2
paste -d data1 data2 gt masterdata
paste -d12 file1 file2 file3 gt file123

132
The 'join' Command

In contrast to the 'paste' command which joins
corresponding lines from several files, the
'join' command joins lines of files that match on
a specified field

133
Using the 'join' command

join -t file1 file2
join -j1 n -j2 m file1 file2

134
Database Operations for Text Files

Using the commands and filters discussed thus
far, very complex file manipulations and queries
are possible files may be cut, pasted, sorted,
counted, and output created to meet many data
processing needs

135
APPENDIX I