








      AA TTuuttoorriiaall IInnttrroodduuccttiioonn ttoo tthhee UUNNIIXX TTeexxtt EEddiittoorr



                      _B_. _W_. _K_e_r_n_i_g_h_a_n

           Bell Laboratories, Murray Hill, N. J.


IInnttrroodduuccttiioonn

     _E_d  is  a ``text editor'', that is, an interactive pro-
gram for creating and modifying ``text'',  using  directions
provided by a user at a terminal.  The text is often a docu-
ment like this one, or a program or perhaps data for a  pro-
gram.

     This  introduction  is  meant  to simplify learning _e_d_.
The recommended way to learn _e_d is to  read  this  document,
simultaneously using _e_d to follow the examples, then to read
the description in section I of the  UNIX  manual,  all  the
while  experimenting  with _e_d_.  (Solicitation of advice from
experienced users is also useful.)

     Do the exercises!  They cover material  not  completely
discussed  in  the  actual text.  An appendix summarizes the
commands.

DDiissccllaaiimmeerr

     This is an introduction and a tutorial.  For this  rea-
son,  no  attempt  is  made to cover more than a part of the
facilities that _e_d offers (although this  fraction  includes
the  most useful and frequently used parts).  Also, there is
not enough space to explain basic UNIX procedures.  We  will
assume  that  you  know  how to log on to UNIX, and that you
have at least a vague understanding of what a file is.

     You must also know what character to type as  the  end-
of-line  on your particular terminal.  This is a ``newline''
on Model  37  Teletypes,  and  ``return''  on  most  others.
Throughout, we will refer to this character, whatever it is,
as ``newline''.

GGeettttiinngg SSttaarrtteedd

     We'll assume that you have logged in to UNIX and it has
just said ``%''.  The easiest way to get _e_d is to type
   ed   (followed by a newline)
You  are  now ready to go - _e_d is waiting for you to tell it
what to do.









                             -2-


CCrreeaattiinngg TTeexxtt -- tthhee AAppppeenndd ccoommmmaanndd ````aa''''

     As our first problem, suppose we want  to  create  some
text  starting from scratch.  Perhaps we are typing the very
first draft of a paper; clearly it will have to start  some-
where,  and  undergo modifications later.  This section will
show how to get some text in, just to  get  started.   Later
we'll talk about how to change it.

     When  _e_d  is  first  started, it is rather like working
with a blank piece of paper - there is no text  or  informa-
tion present.  This must be supplied by the person using _e_d_;
it is usually done by typing in the text, or by  reading  it
into  _e_d from a file.  We will start by typing in some text,
and return shortly to how to read files.

     First a bit of terminology.  In  _e_d  jargon,  the  text
being  worked  on is said to be ``kept in a buffer.''  Think
of the buffer as a work space, if you like, or simply as the
information that you are going to be editing.  In effect the
buffer is like the piece of paper, on which  we  will  write
things, then change some of them, and finally file the whole
thing away for another day.

     The user tells _e_d what to do  to  his  text  by  typing
instructions  called ``commands.''  Most commands consist of
a single letter, which must be typed in  lower  case.   Each
command is typed on a separate line.  (Sometimes the command
is preceded by information about what line or lines of  text
are  to  be  affected  - we will discuss these shortly.)  _E_d
makes no response to most commands - there is  no  prompting
or typing of messages like ``ready''.  (This silence is pre-
ferred by experienced users,  but  sometimes  a  hangup  for
beginners.)

     The first command is _a_p_p_e_n_d_, written as the letter
   a
all by itself.  It means ``append (or add) text lines to the
buffer, as I type them in.''  Appending is rather like writ-
ing fresh material on a piece of paper.

     So to enter lines of text into the buffer, we just type
an ``a'' followed by a newline, followed  by  the  lines  of
text we want, like this:
   a
   Now is the time
   for all good men
   to come to the aid of their party.
   ..

     The  only  way to stop appending is to type a line that
contains only a period.  The ``..'' is used to tell  _e_d  that
we  have finished appending.  (Even experienced users forget
that terminating  ``..''   sometimes.   If  _e_d  seems  to  be









                             -3-


ignoring you, type an extra line with just ``..'' on it.  You
may then find you've added some garbage lines to your  text,
which you'll have to take out later.)

     After the append command has been done, the buffer will
contain the three lines
   Now is the time
   for all good men
   to come to the aid of their party.
The ``a'' and ``..'' aren't there, because they are not text.

     To  add  more  text to what we already have, just issue
another ``a'' command, and continue typing.

EErrrroorr MMeessssaaggeess -- ````??''''

     If at any time you make an error in  the  commands  you
type to _e_d_, it will tell you by typing
   ?
This  is  about  as cryptic as it can be, but with practice,
you can usually figure out how you goofed.

WWrriittiinngg tteexxtt oouutt aass aa ffiillee -- tthhee WWrriittee ccoommmmaanndd ````ww''''

     It's likely that we'll want to save our text for  later
use.   To  write out the contents of the buffer onto a file,
we use the _w_r_i_t_e command
   w
followed by the filename we want to  write  on.   This  will
copy the buffer's contents onto the specified file (destroy-
ing any previous information on the file).  To save the text
on a file named ``junk'', for example, type
   w junk
Leave  a  space  between  ``w''  and the file name.  _E_d will
respond by printing the number of characters it  wrote  out.
In our case, _e_d would respond with
   68
(Remember  that  blanks and the newline character at the end
of each line are included in the character count.)   Writing
a file just makes a copy of the text - the buffer's contents
are not disturbed, so we can go on adding lines to it.  This
is an important point.  _E_d at all times works on a copy of a
file, not the file itself.  No change in the contents  of  a
file  takes  place until you give a ``w'' command.  (Writing
out the text onto a file from time to time as  it  is  being
created  is  a  good idea, since if the system crashes or if
you make some horrible mistake, you will lose all  the  text
in  the  buffer but any text that was written onto a file is
relatively safe.)

LLeeaavviinngg eedd -- tthhee QQuuiitt ccoommmmaanndd ````qq''''

     To terminate a session with _e_d_, save  the  text  you're
working  on  by  writing  it  onto  a  file  using the ``w''









                             -4-


command, and then type the command
   q
which stands for _q_u_i_t_.  The system will respond with  ``%''.
At this point your buffer vanishes, with all its text, which
is why you want to write it out before quitting.

EExxeerrcciissee 11::

     Enter _e_d and create some text using
   a
   ...li
   ..
Write it out using ``w''.  Then leave _e_d with the ``q'' com-
mand,  and  print  the  file, to see that everything worked.
(To print a file, say
   pr filename
or
   cat filename
in response to ``%''.  Try both.)

RReeaaddiinngg tteexxtt ffrroomm aa ffiillee -- tthhee EEddiitt ccoommmmaanndd ````ee''''

     A common way to get text into the buffer is to read  it
from a file in the file system.  This is what you do to edit
text that you saved with the ``w''  command  in  a  previous
session.  The _e_d_i_t command ``e'' fetches the entire contents
of a file into the buffer.  So if we  had  saved  the  three
lines  ``Now is the time'', etc., with a ``w'' command in an
earlier session, the _e_d command
   e junk
would fetch the entire contents of the  file  ``junk''  into
the buffer, and respond
   68
which  is the number of characters in ``junk''.  _I_f _a_n_y_t_h_i_n_g
_w_a_s _a_l_r_e_a_d_y _i_n _t_h_e _b_u_f_f_e_r_, _i_t _i_s _d_e_l_e_t_e_d _f_i_r_s_t_.

     If we use the ``e'' command to read  a  file  into  the
buffer,  then we need not use a file name after a subsequent
``w'' command; _e_d remembers the last file name  used  in  an
``e''  command,  and  ``w'' will write on this file.  Thus a
common way to operate is
   ed
   e file
   [editing session]
   w
   q

     You can find out at any  time  what  file  name  _e_d  is
remembering  by typing the _f_i_l_e command ``f''.  In our case,
if we typed
   f
_e_d would reply
   junk










                             -5-


RReeaaddiinngg tteexxtt ffrroomm aa ffiillee -- tthhee RReeaadd ccoommmmaanndd ````rr''''

     Sometimes we want to read a file into the buffer  with-
out destroying anything that is already there.  This is done
by the _r_e_a_d command ``r''.  The command
   r junk
will read the file ``junk'' into the buffer; it adds  it  to
the end of whatever is already in the buffer.  So if we do a
read after an edit:
   e junk
   r junk
the buffer will contain _t_w_o copies of the text (six  lines).
   Now is the time
   for all good men
   to come to the aid of their party.
   Now is the time
   for all good men
   to come to the aid of their party.
Like  the  ``w'' and ``e'' commands, ``r'' prints the number
of characters read in, after the reading operation  is  com-
plete.

     Generally speaking, ``r'' is much less used than ``e''.

EExxeerrcciissee 22::

     Experiment with the ``e'' command  -  try  reading  and
printing  various  files.  You may get an error ``?'', typi-
cally because you spelled the file name wrong.   Try  alter-
nately  reading  and  appending  to see that they work simi-
larly.  Verify that
   ed filename
is exactly equivalent to
   ed
   e filename
What does
   f filename
do?

PPrriinnttiinngg tthhee ccoonntteennttss ooff tthhee  bbuuffffeerr  --  tthhee  PPrriinntt  ccoommmmaanndd
````pp''''

     To  _p_r_i_n_t  or list the contents of the buffer (or parts
of it) on the terminal, we use the print command
   p
The way this is done is as follows.  We  specify  the  lines
where we want printing to begin and where we want it to end,
separated by a comma, and  followed  by  the  letter  ``p''.
Thus  to  print the first two lines of the buffer, for exam-
ple, (that is, lines 1 through 2) we say
   1,2p (starting line=1, ending line=2 p)
_E_d will respond with
   Now is the time
   for all good men









                             -6-


     Suppose we want to print _a_l_l the lines in  the  buffer.
We could use ``1,3p'' as above if we knew there were exactly
3 lines in the buffer.  But in general, we  don't  know  how
many  there  are, so what do we use for the ending line num-
ber?  _E_d provides a shorthand symbol for  ``line  number  of
last  line in buffer'' - the dollar sign ``$''.  Use it this
way:
   1,$p
This will print _a_l_l the lines in the buffer (line 1 to  last
line.)   If  you want to stop the printing before it is fin-
ished, push the DEL or Delete key; _e_d will type
   ?
and wait for the next command.

     To print the _l_a_s_t line of the buffer, we could use
   $,$p
but _e_d lets us abbreviate this to
   $p
We can print any single line by typing the line number  fol-
lowed by a ``p''.  Thus
   1p
produces the response
   Now is the time
which is the first line of the buffer.

     In  fact,  _e_d  lets  us abbreviate even further: we can
print any single line by typing _j_u_s_t the line  number  -  no
need to type the letter ``p''.  So if we say
   $
_e_d will print the last line of the buffer for us.

     We can also use ``$'' in combinations like
   $-1,$p
which  prints  the last two lines of the buffer.  This helps
when we want to see how far we got in typing.

EExxeerrcciissee 33::

     As before, create some text using  the  append  command
and  experiment  with the ``p'' command.  You will find, for
example, that you can't print line 0 or a  line  beyond  the
end  of  the  buffer, and that attempts to print a buffer in
reverse order by saying
   3,1p
don't work.

TThhee ccuurrrreenntt lliinnee -- ````DDoott'''' oorr ````..''''

     Suppose our buffer still  contains  the  six  lines  as
above, that we have just typed
   1,3p
and _e_d has printed the three lines for us.  Try typing just
   p    (no line numbers).
This will print









                             -7-


   to come to the aid of their party.
which  is  the  third line of the buffer.  In fact it is the
last (most recent) line that we  have  done  anything  with.
(We  just  printed  it!)   We  can repeat this ``p'' command
without line numbers, and it will continue to print line  3.

     The  reason  is  that _e_d maintains a record of the last
line that we did anything to (in this case, line 3, which we
just  printed) so that it can be used instead of an explicit
line number.  This most recent line is referred  to  by  the
shorthand symbol
   ..    (pronounced ``dot'').
Dot is a line number in the same way that ``$'' is; it means
exactly ``the current line'', or loosely, ``the line we most
recently  did something to.''  We can use it in several ways
- one possibility is to say
   ..,$p
This will print all the lines from (including)  the  current
line  to the end of the buffer.  In our case these are lines
3 through 6.

     Some commands change the value of dot, while others  do
not.   The  print command sets dot to the number of the last
line printed; by our last command, we  would  have  ``..''  =
``$'' = 6.

     Dot  is most useful when used in combinations like this
one:
   ..+1  (or equivalently, ..+1p)
This means ``print the next line'' and gives us a handy  way
to step slowly through a buffer.  We can also say
   ..-1  (or ..-1p )
which  means  ``print  the  line  _b_e_f_o_r_e the current line.''
This enables us to go backwards if we wish.  Another  useful
one is something like
   ..-3,..-1p
which prints the previous three lines.

     Don't forget that all of these change the value of dot.
You can find out what dot is at any time by typing
   ..=
_E_d will respond by printing the value of dot.

     Let's summarize some things about the ``p'' command and
dot.   Essentially  ``p'' can be preceded by 0, 1, or 2 line
numbers.  If there is no line number given,  it  prints  the
``current  line'', the line that dot refers to.  If there is
one line number given (with or without the letter ``p''), it
prints  that  line  (and dot is set there); and if there are
two line numbers, it prints all the lines in that range (and
sets dot to the last line printed.)  If two line numbers are
specified the first can't be bigger  than  the  second  (see
Exercise 2.)










                             -8-


     Typing a single newline will cause printing of the next
line - it's equivalent to ``..+1p''.   Try  it.   Try  typing
``^'' - it's equivalent to ``..-1p''.

DDeelleettiinngg lliinneess:: tthhee ````dd'''' ccoommmmaanndd

     Suppose  we want to get rid of the three extra lines in
the buffer.  This is done by the _d_e_l_e_t_e command
   d
Except that ``d'' deletes lines instead  of  printing  them,
its  action  is  similar  to that of ``p''.  The lines to be
deleted are specified for ``d''  exactly  as  they  are  for
``p'':
   _s_t_a_r_t_i_n_g _l_i_n_e_, _e_n_d_i_n_g _l_i_n_e d
Thus the command
   4,$d
deletes  lines 4 through the end.  There are now three lines
left, as we can check by using
   1,$p
And notice that ``$'' now is line 3!  Dot is set to the next
line  after  the  last  line  deleted,  unless the last line
deleted is the last line in the buffer.  In that  case,  dot
is set to ``$''.

EExxeerrcciissee 44::

     Experiment  with ``a'', ``e'', ``r'', ``w'', ``p'', and
``d'' until you are sure that you know  what  they  do,  and
until  you  understand  how dot, ``$'', and line numbers are
used.

     If you are adventurous, try  using  line  numbers  with
``a'',  ``r'',  and ``w'' as well.  You will find that ``a''
will append lines _a_f_t_e_r the line  number  that  you  specify
(rather  than  after  dot); that ``r'' reads a file in _a_f_t_e_r
the line number you specify (not necessarily at the  end  of
the buffer); and that ``w'' will write out exactly the lines
you specify, not necessarily the whole buffer.  These varia-
tions  are  sometimes  handy.  For instance you can insert a
file at the beginning of a buffer by saying
   0r filename
and you can enter lines at the beginning of  the  buffer  by
saying
   0a
   ...li
   ..
Notice that ``..w'' is _v_e_r_y different from
   ..
   w

MMooddiiffyyiinngg tteexxtt:: tthhee SSuubbssttiittuuttee ccoommmmaanndd ````ss''''

     We  are  now  ready to try one of the most important of
all commands - the substitute command









                             -9-


   s
This is the command that is used to change individual  words
or  letters  within a line or group of lines.  It is what we
use, for example, for correcting spelling mistakes and  typ-
ing errors.

     Suppose that by a typing error, line 1 says
   Now is th time
-  the ``e'' has been left off ``the''.  We can use ``s'' to
fix this up as follows:
   1s/th/the/
This says: ``in line 1, substitute for the  characters  `th'
the  characters  `the'.''   To verify that it works (_e_d will
not print the result automatically) we say
   p
and get
   Now is the time
which is what we wanted.  Notice that dot must have been set
to  the  line  where  the substitution took place, since the
``p'' command printed that line.  Dot is always set this way
with the ``s'' command.

     The general way to use the substitute command is
   _s_t_a_r_t_i_n_g_-_l_i_n_e_, _e_n_d_i_n_g_-_l_i_n_e s/_c_h_a_n_g_e _t_h_i_s/_t_o _t_h_i_s/
Whatever  string  of characters is between the first pair of
slashes is replaced by whatever is between the second  pair,
in  _a_l_l  the  lines  between  starting line and ending line.
Only the first occurrence on each line is changed,  however.
If you want to change _e_v_e_r_y occurrence, see Exercise 5.  The
rules for line numbers are the  same  as  those  for  ``p'',
except that dot is set to the last line changed.  (But there
is a trap for the unwary: if no substitution took place, dot
is _n_o_t changed.  This causes an error ``?'' as a warning.)

     Thus we can say
   1,$s/speling/spelling/
and  correct  the first spelling mistake on each line in the
text.  (This is useful for people who  are  consistent  mis-
spellers!)

     If no line numbers are given, the ``s'' command assumes
we mean ``make the substitution on line dot'', so it changes
things  only  on  the  current line.  This leads to the very
common sequence
   s/something/something else/p
which makes some correction on the current  line,  and  then
prints  it, to make sure it worked out right.  If it didn't,
we can try again.  (Notice that we put a  print  command  on
the same line as the substitute.  With few exceptions, ``p''
can follow any command; no  other  multi-command  lines  are
legal.)

     It's also legal to say
   s/ . . . //









                            -10-


which means ``change the first string of characters to _n_o_t_h_-
_i_n_g'', i.e., remove them.  This is useful for deleting extra
words  in  a line or removing extra letters from words.  For
instance, if we had
   Nowxx is the time
we can say
   s/xx//p
to get
   Now is the time
Notice that ``//''  here  means  ``no  characters'',  not  a
blank.  There _i_s a difference!  (See below for another mean-
ing of ``//''.)

EExxeerrcciissee 55::

     Experiment with the substitute command.  See what  hap-
pens  if you substitute for some word on a line with several
occurrences of that word.  For example, do this:
   a
   the other side of the coin
   ..
   s/the/on the/p
You will get
   on the other side of the coin
A substitute command changes only the  first  occurrence  of
the  first string.  You can change all occurrences by adding
a ``g'' (for ``global'') to the ``s'' command, like this:
   s/ . . . / . . . /gp
Try other characters instead of slashes to delimit  the  two
sets  of  characters  in the ``s'' command - anything should
work except blanks or tabs.

     (If you get funny results using any of the characters
   ^    ..    $    [    *    \
read the section on ``Special Characters''.)

CCoonntteexxtt sseeaarrcchhiinngg -- ````// .. .. .. //''''

     With the substitute command mastered, we can move on to
another highly important idea of _e_d - context searching.

     Suppose  we  have  our  original three line text in the
buffer:
   Now is the time
   for all good men
   to come to the aid of their party.
Suppose we want to find the line that contains ``their''  so
we  can  change it to ``the''.  Now with only three lines in
the buffer, it's pretty easy to keep track of what line  the
word  ``their''  is on.  But if the buffer contained several
hundred lines, and we'd been making  changes,  deleting  and
rearranging lines, and so on, we would no longer really know
what this line number would be.  Context searching is simply
a  method of specifying the desired line, regardless of what









                            -11-


its number is, by specifying some context on it.

     The way we say ``search for a line that  contains  this
particular string of characters'' is to type
   /_s_t_r_i_n_g _o_f _c_h_a_r_a_c_t_e_r_s _w_e _w_a_n_t _t_o _f_i_n_d/
For example, the _e_d line
   /their/
is  a context search which is sufficient to find the desired
line - it will locate the next occurrence of the  characters
between  slashes (``their'').  It also sets dot to that line
and prints the line for verification:
   to come to the aid of their party.
``Next occurrence'' means that _e_d  starts  looking  for  the
string  at  line ``..+1'', searches to the end of the buffer,
then continues at line 1 and searches to  line  dot.   (That
is,  the search ``wraps around'' from ``$'' to 1.)  It scans
all the lines in  the  buffer  until  it  either  finds  the
desired line or gets back to dot again.  If the given string
of characters can't be found in any line, _e_d types the error
message
   ?
Otherwise it prints the line it found.

     We  can  do  both the search for the desired line _a_n_d a
substitution all at once, like this:
   /their/s/their/the/p
which will yield
   to come to the aid of the party.
There were three parts to that last command: context  search
for the desired line, make the substitution, print the line.

     The expression ``/their/'' is a context search  expres-
sion.   In  their  simplest form, all context search expres-
sions are like this - a string of characters  surrounded  by
slashes.   Context  searches  are  interchangeable with line
numbers, so they can be used by themselves to find and print
a  desired  line, or as line numbers for some other command,
like ``s''.  We used them both ways in the examples above.

     Suppose the buffer contains the three familiar lines
   Now is the time
   for all good men
   to come to the aid of their party.
Then the _e_d line numbers
   /Now/+1
   /good/
   /party/-1
are all context search expressions, and they  all  refer  to
the  same  line  (line  2).   To make a change in line 2, we
could say
   /Now/+1s/good/bad/
or
   /good/s/good/bad/
or









                            -12-


   /party/-1s/good/bad/
The choice is dictated only by convenience.  We could  print
all three lines by, for instance
   /Now/,/party/p
or
   /Now/,/Now/+2p
or  by any number of similar combinations.  The first one of
these might be better if we don't know how  many  lines  are
involved.  (Of course, if there were only three lines in the
buffer, we'd use
   1,$p
but not if there were several hundred.)

     The basic rule is: a context search expression  is  _t_h_e
_s_a_m_e  _a_s  a  line  number, so it can be used wherever a line
number is needed.

EExxeerrcciissee 66::

     Experiment with context searching.  Try a body of  text
with  several  occurrences of the same string of characters,
and scan through it using the same context search.

     Try using context searches as line numbers for the sub-
stitute,  print and delete commands.  (They can also be used
with ``r'', ``w'', and ``a''.)

     Try  context  searching  using  ``?text?''  instead  of
``/text/''.  This scans lines in the buffer in reverse order
rather than normal.  This is sometimes useful if you go  too
far  while  looking  for some string of characters - it's an
easy way to back up.

     (If you get funny results with any of the characters
   ^    ..    $    [    *    \
read the section on ``Special Characters''.)

     _E_d provides a shorthand for repeating a context  search
for the same string.  For example, the _e_d line number
   /string/
will  find the next occurrence of ``string''.  It often hap-
pens that this is not the desired line, so the  search  must
be repeated.  This can be done by typing merely
   //
This  shorthand  stands for ``the most recently used context
search expression.''  It can  also  be  used  as  the  first
string of the substitute command, as in
   /string1/s//string2/
which  will  find  the  next  occurrence  of ``string1'' and
replace it by ``string2''.  This can save a lot  of  typing.
Similarly
   ??
means ``scan backwards for the same expression.''










                            -13-


CChhaannggee aanndd IInnsseerrtt -- ````cc'''' aanndd ````ii''''

     This section discusses the _c_h_a_n_g_e command
   c
which  is  used  to change or replace a group of one or more
lines, and the _i_n_s_e_r_t command
   i
which is used for inserting a group of one or more lines.

     ``Change'', written as
   c
is used to replace a number of lines with  different  lines,
which  are typed in at the terminal.  For example, to change
lines ``..+1'' through ``$'' to something else, type
    .+1,$c
    . . . _t_y_p_e _t_h_e _l_i_n_e_s _o_f _t_e_x_t _y_o_u _w_a_n_t _h_e_r_e . . .
    ..
The lines you type between the ``c'' command and  the  ``..''
will take the place of the original lines between start line
and end line.  This is most useful in replacing  a  line  or
several lines which have errors in them.

     If  only  one  line  is specified in the ``c'' command,
then just that line is replaced.  (You can type in  as  many
replacement  lines as you like.)  Notice the use of ``..'' to
end the input - this works just like the ``..'' in the append
command and must appear by itself on a new line.  If no line
number is given, line dot is replaced.  The value of dot  is
set to the last line you typed in.

     ``Insert'' is similar to append - for instance
   /string/i
   ...li
   ..
will  insert  the  given text _b_e_f_o_r_e the next line that con-
tains ``string''.  The  text  between  ``i''  and  ``..''  is
_i_n_s_e_r_t_e_d  _b_e_f_o_r_e  the  specified line.  If no line number is
specified dot  is  used.   Dot  is  set  to  the  last  line
inserted.

EExxeerrcciissee 77::

     ``Change''  is rather like a combination of delete fol-
lowed by insert.  Experiment to verify that
   _s_t_a_r_t_, _e_n_d d
   i
    _. _. _. _t_e_x_t _. _. _.
   ..
is almost the same as
   _s_t_a_r_t_, _e_n_d c
    _. _. _. _t_e_x_t _. _. _.
   ..
These are not _p_r_e_c_i_s_e_l_y the same if line ``$'' gets deleted.
Check this out.  What is dot?









                            -14-


     Experiment  with  ``a'' and ``i'', to see that they are
similar, but not the same.  You will observe that
   _l_i_n_e_-_n_u_m_b_e_r a
   ...li
   ..
appends _a_f_t_e_r the given line, while
   _l_i_n_e_-_n_u_m_b_e_r i
   ...li
   ..
inserts _b_e_f_o_r_e it.  Observe that if no line number is given,
``i''  inserts  before  line  dot, while ``a'' appends after
line dot.

MMoovviinngg tteexxtt aarroouunndd:: tthhee ````mm'''' ccoommmmaanndd

     The move command ``m'' is used for cutting and  pasting
-  it  lets  you  move  a  group  of lines from one place to
another in the buffer.  Suppose we want  to  put  the  first
three  lines  of the buffer at the end instead.  We could do
it by saying:
   1,3w temp
   $r temp
   1,3d
(Do you see why?)  but we can do it a lot  easier  with  the
``m'' command:
   1,3m$
The general case is
   _s_t_a_r_t _l_i_n_e_, _e_n_d _l_i_n_e m _a_f_t_e_r _t_h_i_s _l_i_n_e
Notice  that  there  is  a  third line to be specified - the
place where the moved stuff gets put.  Of course  the  lines
to be moved can be specified by context searches; if we had
   First paragraph
   ..end of first paragraph.
   Second paragraph
   ..end of second paragraph.
we could reverse the two paragraphs like this:
   /Second/,/second/m/First/-1
Notice  the ``-1'' - the moved text goes _a_f_t_e_r the line men-
tioned.  Dot gets set to the last line moved.

TThhee gglloobbaall ccoommmmaannddss ````gg'''' aanndd ````vv''''

     The _g_l_o_b_a_l command ``g'' is used to execute one or more
_e_d commands on all those lines in the buffer that match some
specified string.  For example
   g/peling/p
prints all lines that contain ``peling''.  More usefully,
   g/peling/s//pelling/gp
makes the substitution everywhere on the line,  then  prints
each corrected line.  Compare this to
   1,$s/peling/pelling/gp
which only prints the last line substituted.  Another subtle
difference is that the ``g'' command does not give  a  ``?''
if ``peling'' is not found where the ``s'' command will.









                            -15-


     There  may  be several commands (including ``a'', ``c''
``i'' ``r'', ``w'', but not ``g''); in that case, every line
except the last must end with a backslash ``\'':
   g/xxx/..-1s/abc/def/\
   ..+2s/ghi/jkl/\
   ..-2,..p
makes  changes  in the lines before and after each line that
contains ``xxx'', then prints all three lines.

     The ``v'' command is the same as ``g'', except that the
commands  are executed on every line that does _n_o_t match the
string following ``v'':
   v/ /d
deletes every line that does not contain a blank.

SSppeecciiaall CChhaarraacctteerrss

     You may have noticed that things just don't work  right
when  you used some characters like ``.'', ``*'', ``$'', and
others in context searches and the substitute command.   The
reason  is  rather  complex,  although  the  cure is simple.
Basically, _e_d treats these characters as special, with  spe-
cial  meanings.   For  instance,  _i_n _a _c_o_n_t_e_x_t _s_e_a_r_c_h _o_r _t_h_e
_f_i_r_s_t _s_t_r_i_n_g _o_f _t_h_e _s_u_b_s_t_i_t_u_t_e _c_o_m_m_a_n_d _o_n_l_y_, ..  means  ``any
character,'' not a period, so
   /x..y/
means  ``a  line  with  an  x, _a_n_y _c_h_a_r_a_c_t_e_r_, and a y,'' _n_o_t
just ``a line with an x, a period, and a  y.''~  A  complete
list of the special characters that can cause trouble is the
following:
   ^    ..    $    [    *    \
_W_a_r_n_i_n_g_: The backslash character \ is special  to  _e_d_.   For
safety's  sake, avoid it where possible.  If you have to use
one of the special characters in a substitute  command,  you
can  turn  off its magic meaning temporarily by preceding it
with the backslash.  Thus
   s/\\\..\*/backslash dot star/
will change ``\..*'' into ``backslash dot star''.

     Here is a hurried synopsis of the other special charac-
ters.  First, the circumflex `` ^ '' signifies the beginning
of a line.  Thus
   /^string/
finds ``string'' only if it is at the beginning of  a  line:
it will find
   string
but not
   the string...
The  dollar-sign  ``$''  is just the opposite of the circum-
flex; it means the end of a line:
   /string$/
will only find an occurrence of ``string'' that  is  at  the
end of some line.  This implies, of course, that
   /^string$/









                            -16-


will find only a line that contains just ``string'', and
   /^..$/
finds a line containing exactly one character.

     The  character  ``..'',  as  we mentioned above, matches
anything;
   /x..y/
matches any of
   x+y
   x-y
   x y
   x..y
This is useful in conjunction with ``*'', which is a repeti-
tion  character;  ``a*''  is a shorthand for ``any number of
a's,'' so ``..*'' matches any number of anythings.   This  is
used like this:
   s/..*/stuff/
which changes an entire line, or
   s/..*,//
which deletes all characters in the line up to and including
the last comma.  (Since ``..*'' finds  the  longest  possible
match, this goes up to the last comma.)

     ``['' is used with ``]'' to form ``character classes'';
for example,
   /[1234567890]/
matches any single digit _ any one of the characters  inside
the braces will cause a match.

     Finally,  the ``&'' is another shorthand character - it
is used only on the right-hand part of a substitute  command
where  it  means  ``whatever  was  matched  on the left-hand
side''.  It is used to save  typing.   Suppose  the  current
line contained
   Now is the time
and  we  wanted to put parentheses around it.  We could just
retype the line, but this is tedious.  Or we could say
   s/^/(/
   s/$/)/
using our knowledge of ``^'' and ``$''.  But the easiest way
uses the ``&'':
   s/..*/(&)/
This  says  ``match the whole line, and replace it by itself
surrounded by parens.''~ The ``&'' can be used several times
in a line; consider using
   s/..*/&?  &!!/
to produce
   Now is the time?  Now is the time!!

     We  don't  have  to match the whole line, of course: if
the buffer contains
   the end of the world
we could type
   /world/s//& is at hand/









                            -17-


to produce
   the end of the world is at hand
Observe this expression carefully, for it illustrates how to
take advantage of _e_d to save typing.  The string ``/world/''
found the desired line; the shorthand ``//'' found the  same
word  in  the  line;  and  the ``&'' saved us from typing it
again.

     The ``&''  is  a  special  character  only  within  the
replacement text of a substitute command, and has no special
meaning elsewhere.  We can turn off the special  meaning  of
``&'' by preceding it with a ``\'':
   s/ampersand/\&/
will  convert the word ``ampersand'' into the literal symbol
``&'' in the current line.



SSuummmmaarryy ooff CCoommmmaannddss aanndd LLiinnee NNuummbbeerrss

     The general form of _e_d commands is  the  command  name,
perhaps  preceded  by  one  or two line numbers, and, in the
case of _e_, _r and _w_, followed by a file name.  Only one  com-
mand  is  allowed  per  line, but a _p command may follow any
other command (except for _e_, _r_, _w and _q_)_.

_a _(_a_p_p_e_n_d_) Add lines to the buffer (at line  dot,  unless  a
different  line  is  specified).  Appending  continues until
``..''  is typed on a new line.  Dot is set to the last  line
appended.
_c  _(_c_h_a_n_g_e_) Change the specified lines to the new text which
follows.  The new lines are terminated by a  ``..''.   If  no
lines  are  specified, replace line dot.  Dot is set to last
line changed.
_d _(_d_e_l_e_t_e_) Delete the lines specified.  If none  are  speci-
fied,  delete  line  dot.  Dot is set to the first undeleted
line, unless ``$'' is deleted, in which case dot is  set  to
``$''.
_e _(_e_d_i_t_) Edit new file.  Any previous contents of the buffer
are thrown away, so issue a _w beforehand if you want to save
them.
_f _(_f_i_l_e_) Print remembered filename.  If a name follows _f the
remembered name will be set to it.
_g _(_g_l_o_b_a_l_) _g_/_-_-_-_/_c_o_m_m_a_n_d_s will execute the commands on those
lines  that contain ``---'', which can be any context search
expression.
_i _(_i_n_s_e_r_t_) Insert lines before specified line (or dot) until
a  ``..''  is  typed  on a new line.  Dot is set to last line
inserted.
_m _(_m_o_v_e_) Move lines specified to after the line named  after
_m_.  Dot is set to the last line moved.
_p  _(_p_r_i_n_t_)  Print specified lines.  If none specified, print
line dot.  A single line number is equivalent to ``line-num-
ber p''.  A single newline prints ``..+1'', the next line.









                            -18-


_q _(_q_u_i_t_) Exit from ed.  Wipes out all text in buffer!!
_r  _(_r_e_a_d_)  Read  a file into buffer (at end unless specified
elsewhere.) Dot set to last line read.
_s _(_s_u_b_s_t_i_t_u_t_e_) _s_/_s_t_r_i_n_g_1_/_s_t_r_i_n_g_2_/ will substitute the  char-
acters of `string2' for `string1' in specified lines.  If no
line is specified, make substitution in line  dot.   Dot  is
set  to  last line in which a substitution took place, which
means that  if  no  substitution  took  place,  dot  is  not
changed.   _s changes only the first occurrence of string1 on
a line; to change all of them, type a ``g'' after the  final
slash.
_v  _(_e_x_c_l_u_d_e_)  _v_/_-_-_-_/_c_o_m_m_a_n_d_s  executes ``commands'' on those
lines that _d_o _n_o_t contain ``---''.
_w _(_w_r_i_t_e_) Write out buffer onto a file.  Dot is not changed.
_P_r_i_n_t  _v_a_l_u_e  _o_f  _d_o_t_.  (``='' by itself prints the value of
``$''.)
_! _(_t_e_m_p_o_r_a_r_y _e_s_c_a_p_e_)
   Execute this line as a UNIX command.
_/_-_-_-_-_-_/ Context search.  Search for next line which contains
this  string  of  characters.  Print it.  Dot is set to line
where string found.  Search starts at ``..+1'', wraps  around
from ``$'' to 1, and continues to dot, if necessary.
_?_-_-_-_-_-_?   Context search in reverse direction.  Start search
at ``..-1'', scan to 1, wrap around to ``$''.




































