11/3/71 ED (I)
NAME ed -- editor
SYNOPSIS ed [ name ]
DESCRIPTION ed is the standard text editor. ed is based on
QED [reference] but is fully if succinctly de-
scribed here. Differences between ed and QED are
also noted to simplify the transition to the less
powerful editor.
If the optional argument is given, ed simulates
an e command on the named file; that is to say,
the file is read into ed's buffer so that it can
be edited.
ed operates on a copy of any file it is editing;
changes made in the copy have no effect on the
file until an explicit write (w) command is
given. The copy of the text being edited resides
in a temporary file called the buffer. There is
only one buffer.
Commands to ed have a simple and regular struc-
ture: zero or more addresses followed by a single
character command, possibly followed by parame-
ters to the command. These addresses specify one
or more lines in the buffer. Every command which
requires addresses has default addresses, so that
the addresses can often be omitted.
In general only one command may appear on a line.
Certain commands allow the input of text. This
text is placed in the appropriate place in the
buffer. While ed is accepting text, it is said
to be in input mode. In this mode, no commands
are recognized; all input is merely collected.
Input mode is left by typing a period (.) alone
at the beginning of a line.
ed supports a limited form of regular expression
notation. A regular expression is an expression
which specifies a set of strings of characters.
A member of this set of strings is said to be
matched by the regular expression. The regular
expressions allowed by ed are constructed as fol-
lows:
1. An ordinary character (not one of those
discussed below) is a regular expression
and matches that character.
2. A circumflex (^) at the beginning of a reg-
ular expression matches the null character
at the beginning of a line.
3. A currency symbol ($) at the end of a regu-
lar expression matches the null character
at the end of a line.
4. A period (.) matches any character but a
new-line character.
5. A regular expression followed by an aster-
isk (*) matches any number of adjacent oc-
currences (including zero) of the regular
expression it follows.
6. A string of characters enclosed in square
brackets ([]) matches any character in the
string but no others. If, however, the
first character of the string is a circum-
flex (^) the regular expression matches any
character but new-line and the characters
in the string.
7. The concatenation of regular expressions is
a regular expression which matches the con-
catenation of the strings matched by the
components of the regular expression.
8. The null regular expression standing alone
is equivalent to the last regular expres-
sion encountered.
Regular expressions are used in addresses to
specify lines and in one command (s, see below)
to specify a portion of a line which is to be re-
placed.
If it is desired to use one of the regular ex-
pression metacharacters as an ordinary character,
that character may be preceded by "\". This also
applies to the character bounding the regular ex-
pression (often "/") and to "\" itself.
Addresses are constructed as follows. To under-
stand addressing in ed it is necessary to know
that at any time there is a current line. Gener-
ally speaking, the current line is the last line
affected by a command; however, the exact effect
on the current line by each command is discussed
under the description of the command.
1. The character "." addresses the current
line.
2. The character "$" addresses the last line
of the buffer.
3. A decimal number n addresses the nth line
of the buffer.
4. A regular expression enclosed in slashes
"/" addresses the first line found by
searching toward the end of the buffer and
stopping at the first line containing a
string matching the regular expression. If
necessary the search wraps around to the
beginning of the buffer.
5. A regular expression enclosed in queries
"?" addresses the first line found by
searching toward the beginning of the
buffer and stopping at the first line found
containing a string matching the regular
expression. If necessary the search wraps
around to the end of the buffer.
7. An address followed by a plus sign "+" or a
minus sign "-" followed by a decimal number
specifies that address plus (resp. minus)
the indicated number of lines. The plus
sign may be omitted.
Commands may require zero, one, or two addresses.
Commands which require no addresses regard the
presence of an address as an error. Commands
which require the presence of one address all as-
sume a default address (often ".") but if given
more than one address ignore any extra and use
the last given. Commands which require two ad-
dresses have defaults in the case of zero or one
address but use the last two if more than two are
given.
Addresses are separated from each other typically
by a comma (,). They may also be separated by a
semicolon (;). In this case the current line "."
is set to the the previous address before the
next address is interpreted. This feature is
used to control the starting line for forward and
backward searches ("/", "?").
In the following list of ed commands, the default
addresses are shown in parentheses. The paren-
theses are not part of the address, but are used
to show that the given addresses are the default.
As mentioned, it is generally illegal for more
than one command to appear on a line. However,
any command may be suffixed by "p" (for "print").
In that case, the current line is printed after
the command is complete.
In any two-address command, it is illegal for the
first address to lie after the second address.
(.)a
<text>
.
The append command reads the given text and
appends it after the addressed line. "."
is left on the last line input, if there
were any, otherwise at the addressed line.
Address "0" is legal for this command; text
is placed at the beginning of the buffer.
(NOTE: the default address differs from
that of QED.)
(.,.)c
<text>
.
The change command deletes the addressed
lines, then accepts input text which re-
places these lines. "." is left at the
last line input; if there were none, it is
left at the first line not changed.
(.,.)d
The delete command deletes the addressed
lines from the buffer. "." is left at the
first line not deleted
e filename
The edit command causes the entire contents
of the buffer to be deleted, and then the
named file to be read in. "." is set to
the last line of the buffer. The number of
characters read is typed.
(1,$)g/regular expression/command
In the global command, the first step is to
mark every line which matches the given
regular expression. Then for every such
line, the given command is executed with
"." set to that line. The repeated command
cannot be a, q, i, or c.
(.)i
<text>
.
This command inserts the given text before
the addressed line. "." is left at the
last line input; if there were none, at the
addressed line. This command differs from
the a command only in the placement of the
text.
(.,.)l
The list command prints the addressed lines
in an unambiguous way. Non-printing char-
acters are over-struck as follows:
char prints
bs \
tab >
ret <
SI I
SO O
All character preceded by a prefix (ESC)
character are printed over-struck with ^
without the prefix. Long lines are folded
with the sequence \newline.
(.,.)p
The print command prints the addressed
lines. "." is left at the last line
printed.
q
The quit command causes ed to exit. No au-
tomatic write of a file is done.
($)r filename
The read command reads in the given file
after the addressed line. If no file name
is given, the file last mentioned in e, r,
or w commands is read. Address "0" is le-
gal for r and causes the file to be read at
the beginning of the buffer. If the read
is successful, the number of characters
read is typed. "." is left at the last
line read in from the file.
(.,.)s/regular expression/replacement/
The substitute command searches each ad-
dressed line for an occurrence of the spec-
ified regular expression. On each line in
which a match is found, the first (and only
first, compare QED) matched string is re-
placed by the replacement specified, It is
an error for the substitution to fail on
all addressed lines. Any character other
than space or new-line may be used instead
of "/" to delimit the regular expression
and the replacement. "." is left at the
last line substituted.
The ampersand "&" appearing in the replace-
ment is replaced by the regular expression
that was matched. The special meaning of
"&" in this context may be suppressed by
preceding it by "\".
(1,$)w filename
The write command writes the addressed
lines onto the given file. If no file name
is given, the file last named in e, r, or w
commands is written. "." is unchanged. If
the command is successful, the number of
characters written is typed.
($)=
The line number of the addressed line is
typed. "." is unchanged by this command.
!UNIX command
The remainder of the line after the "!" is
sent to UNIX to be interpreted as a com-
mand. "." is unchanged.
<newline>
A blank line alone is equivalent to ".+1p";
it is useful for stepping through text.
Ed can edit at most 1500 lines and the maximum
size of a line is 256 characters. The differ-
ences between ed and QED are:
1. There is no "\f" character; input mode is
left by typing "." alone on a line.
2. There is only one buffer and hence no "\b"
stream directive.
3. The commands are limited to:
a c d e g i l p q r s w = !
where e is new.
4. The only special characters in regular ex-
pressions are:
* ^ $ [ .
which have the usual meanings. However,
"^" and "$" are only effective if they are
the first or last character respectively of
the regular expression. Otherwise suppres-
sion of special meaning is done by preced-
ing the character by "\", which is not oth-
erwise special.
5. In the substitute command, only the left-
most occurrence of the matched regular ex-
pression is substituted.
7. The a command has a different default ad-
dress.
FILES /tmp/etma, etmb, ... temporary
/etc/msh is used to implement the "!" command.
SEE ALSO --
DIAGNOSTICS "?" for any error
BUGS ed is used as the shell for the editing system.
it has the editing system UID built in and if in-
voked under this UID will give slightly different
responses. This is a little kludgy.
OWNER ken