\"      @(#)e2  6.1 (Berkeley) 5/22/86
\"
SH
Writing text out as a file \- the Write command ``w''
PP
It's likely that you'll want to save your text for later use.
To write out the contents of the buffer onto a file,
use the
ul
write
command
P1
w
P2
followed by the filename you want to write on.
This will copy the buffer's contents
onto the specified file
(destroying any previous information on the file).
To save
the text on a file named
UL junk ,
for example, type
P1
w junk
P2
Leave a space between
UL w
and the file name.
ul
Ed
will respond by printing
the number of characters it wrote out.
In this case,
ul
ed
would respond with
P1
68
P2
(Remember that blanks and the return 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 you can go on adding
lines to it.
This is an important point.
ul
Ed
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
UL 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.)
SH
Leaving ed \- the Quit command ``q''
PP
To terminate a session with
IT ed ,
save the text you're working on
by writing it onto a file using the
UL w
command,
and then type the command
P1
q
P2
which
stands for
IT quit .
The system will respond with
the prompt character
UL $ "" (
or
UL % ).
At
this point your buffer vanishes, with all its text,
which is why you want to write it out before quitting.\(dg
FS
\(dg Actually,
IT ed
will print
UL ?
if you try to quit without writing.
At that point, write if you want;
if not, another
UL q
will get you out regardless.
FE
SH
Exercise 1:
PP
Enter
ul
ed
and
create some text using
P1
a
\&. . . text . . .
\&\fB.\fR
P2
Write it out using
UL w .
Then leave
ul
ed
with the
UL q
command, and print the file,
to see that everything worked.
(To print a file, say
P1
pr filename
P2
or
P1
cat filename
P2
in response to
the prompt character.
Try both.)
SH
Reading text from a file \- the Edit command ``e''
PP
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
UL w
command in a previous session.
The
ul
edit
command
UL e
fetches the entire contents of a file into the buffer.
So if you had saved the three lines
``Now is the time'', etc.,
with a
UL w
command in an earlier session,
the
ul
ed
command
P1
e junk
P2
would fetch the entire contents of the file
UL junk
into the buffer, and respond
P1
68
P2
which is the number of characters in
UL junk .
ul
If anything was already in the buffer, it is deleted first.
PP
If you use the
UL e
command to read a file into the buffer,
then you need not use a file name after a subsequent
UL w
command;
ul
ed
remembers the last file name used in an
UL e
command,
and
UL w
will write on this file.
Thus a good way to operate is
P1
ed
e file
[editing session]
w
q
P2
This way, you can simply say
UL w
from time to time,
and be secure in the knowledge that
if you got the file name right at the beginning,
you are writing into the proper file each time.
PP
You can find out at any time what file name
ul
ed
is remembering by typing the
ul
file
command
UL f .
In this example,
if you typed
P1
f
P2
ul
ed
would reply
P1
junk
P2
SH
Reading text from a file \- the Read command ``r''
PP
Sometimes you want to read a file into the buffer
without destroying anything that is already there.
This is done by the
ul
read
command
UL r .
The command
P1
r junk
P2
will read the file
UL junk
into the buffer;
it adds it
to the end of whatever is already in the buffer.
So if you do a read after
an edit:
P1
e junk
r junk
P2
the buffer will contain
ul
two
copies of the text (six lines).
P1
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.
P2
Like the
UL w
and
UL e
commands,
UL r
prints
the
number of characters read in, after the reading operation is complete.
PP
Generally speaking,
UL r
is much less used than
UL e .
SH
Exercise 2:
PP
Experiment with the
UL e
command \-
try reading and printing various files.
You may get an error
UL ?name ,
where
UL name
is the name of a file;
this means that the file doesn't exist,
typically because you spelled the file name wrong,
or perhaps that you are not allowed to read or write it.
Try alternately reading and appending to see that they work
similarly.
Verify that
P1
ed filename
P2
is exactly equivalent to
P1
ed
e filename
P2
What does
P1
f filename
P2
do?
SH
Printing the contents of the buffer \- the Print command ``p''
PP
To
ul
print
or list the contents of the buffer (or parts
of it) on the terminal, use the print command
P1
p
P2
The way this is done is as follows.
Specify the lines where
you want printing to begin and where you want it to end,
separated by a comma, and
followed by the letter
UL p .
Thus to print the first two lines of the buffer, for
example, (that is, lines 1 through 2) say
P1
1,2p    (starting line=1, ending line=2 p)
P2
ul
Ed
will respond with
P1
Now is the time
for all good men
P2
PP
Suppose you want to print
ul
all
the lines in the buffer.
You could use
UL 1,3p
as above if you knew there were exactly
3 lines in the buffer.
But in general, you don't
know how many there are, so what do you use for the ending
line number?
ul
Ed
provides a shorthand symbol for ``line number of
last line in buffer'' \- the dollar sign
UL $ .
Use it this
way:
P1
1,$p
P2
This will print
ul
all
the lines in the buffer (line 1 to last line.)
If you want to stop the printing before it is finished,
push the
UC DEL
or Delete key;
ul
ed
will type
P1
?
P2
and wait for the next command.
PP
To print the
ul
last
line of the buffer, you could use
P1
$,$p
P2
but
ul
ed
lets you abbreviate this to
P1
$p
P2
You can print any single line by typing the line
number followed by a
UL p .
Thus
P1
1p
P2
produces the response
P1
Now is the time
P2
which is the first line of the buffer.
PP
In fact,
ul
ed
lets you abbreviate even further:
you can print any single line by typing
ul
just
the line number \- no need to type the letter
UL p .
So if you say
P1
$
P2
ul
ed
will print the last line of the buffer.
PP
You can also use
UL $
in combinations like
P1
$\-1,$p
P2
which prints the last two lines of the buffer.
This helps when you want to see how far you got in typing.
SH
Exercise 3:
PP
As before, create some text using the
UL a
command and
experiment with the
UL 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
P1
3,1p
P2
don't work.

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