.TH ED 1 386BSD
.SH NAME
ed \- text editor
.SH SYNOPSIS
ed [-] [-sx] [-p string] [file]
.SH DESCRIPTION
.B ed
is a line-oriented text editor.
It is used to create, display, modify and otherwise manipulate text
files.

If invoked with the
.I file
argument, then a copy of
.I file
is read into the editor's buffer.
Changes are made to this copy and not directly to
.I file
itself.
Upon quitting
.BR ed ,
any changes not explicitly saved  with a
.I `w'
command are lost.

Editing is done in two distinct modes:
.I command 
and 
.IR input .
When first invoked,
.B ed
is in command mode.
In this mode editing commands are read from the standard input and 
executed to manipulate the contents of the editor buffer.
A typical command might look like:
.sp
.RS
,s/\fIold\fR/\fInew\fR/gp
.RE
.sp
which replaces all occurences of the string
.I old
with
.IR new .

When an input command, such as
.I `a'
(append),
.I `i'
(insert) or
.I `c'
(change), is given,
.B ed
enters input mode.  This is the primary means
of adding text to a file.  
In this mode, no commands are available;
instead, the standard input is written 
directly to the editor buffer.  Input mode is terminated by
entering a single period  (\fI.\fR) on a line.

All
.B ed
commands operate on whole lines or ranges of lines; e.g.,
the
.I `d'
command deletes lines; the
.I `m'
command moves lines, and so on.
It is possible to modify only a portion of a line by means of replacement,
as in the example above.  However even here, the
.I `s'
command is applied to whole lines at a time.

In general,
.B ed
commands consist of zero or more line addresses, followed by a single
character command and possibly additional parameters; i.e.,
commands have the structure:
.sp
.RS
.I [address [,address]]command[parameters]
.RE
.sp
The address(es) indicate the line(s) to be affected by the command.
If fewer addresses are given than the command accepts, then default
addresses are supplied.

.SS OPTIONS
.TP 8
-s
Suppresses diagnostics. This should be used if
.BR ed 's
standard input is from a script.

.TP 8
-x
Prompts for an encryption key to be used in subsequent reads and writes
(see the
.I `x'
command).

.TP 8
.RI \-p \ string
Specifies a command prompt.  This may be toggled on and off with the
.I `P'
command.

.TP 8
name
Specifies the name of a file to read.  If 
.I name 
is prefixed with a
bang (!), then it is interpreted as a shell command.  In this case,
what is read is
the standard output of 
.I name 
executed via
.IR sh (1).
To read a file whose name begins with a bang, prefix the
name with a backslash (\\).

.SS LINE ADDRESSING
An address represents the number of line in the buffer.  
.B ed
maintains a 
.I current address 
which is
typically supplied to commands as the default address when none is specified.
When a file is first read,  the current address is set to the last line
of the file.  In general, the current address is set to the last line
affected by a command.

A line address is
constructed from one of the bases in the list below, optionally followed
by a numeric offset.  The offset may include any combination
of digits, operators (i.e., 
.IR + ,
.I -
and
.IR ^ )
and whitespace.
Addresses are read from left to right, and their values are computed
relative to the current address.

One exception to the rule that addresses represent line numbers is the
address 
.I `0'
(zero).
This means "before the first line,"
and is legal wherever it makes sense.

An address range is two addresses separated either by a comma or
semi-colon. The value of the first address in a range cannot exceed the
value of the the second.  If an 
.IR n- tuple 
of addresses is given where
.I n > 2,
then the corresponding range is determined by the last two addresses
in the 
.IR n- tuple.
If only one address is expected, then the last
address is used.

Each address in a comma-delimited range is interpreted relative to the
current address.  In a semi-colon-delimited range, the first address is
used to set the current address, and the second address is interpreted
relative to the first.

The following address symbols are recognized.

.TP 8
\fR.\fR
The current line (address) in the buffer.

.TP 8
$
The last line in the buffer.

.TP 8
n
The
.IR n th,
line in the buffer
where 
.I n
is a number in the range
.I [0,$].

.TP 8
- or ^
The previous line.
This is equivalent to 
.I -1
and may be repeated with cumulative effect.

.TP 8
-\fIn\fR or ^\fIn\fR
The
.IR n th
previous line, where 
.I n
is a non-negative number.

.TP 8
+
The
next line.
This is equivalent to 
.I +1
and may be repeated with cumulative effect.

.TP 8
+\fIn\fR or whitespace\fIn\fR
The
.IR n th
next line, where 
.I n
is a non-negative number.
.I whitespace
followed by a number 
.I n
is interpreted as 
.IR +n .

.TP 8
, \fRor\fB %
The first through last lines in the buffer.  This is equivalent to
the address range
.I 1,$.

.TP 8
;
The
current through last lines in the buffer.  This is equivalent to
the address range
.I .,$.

.TP 8
.RI / re/
The
next line containing the regular expression
.IR re .
The search wraps to the beginning of the buffer and continues down to the
current line, if necessary.
// repeats the last search.

.TP 8
.RI ? re?
The
previous line containing the regular expression
.IR re .
The search wraps to the end of the buffer and continues up to the
current line, if necessary.
?? repeats the last search.

.TP 8
.RI \' lc
The
line previously marked by a
.I `k'
(mark) command, where 
.I lc
is a lower case letter.

.SS REGULAR EXPRESSIONS
Regular expressions are patterns used in selecting text.
For example, the 
.B ed
command
.sp
.RS
g/\fIstring\fR/
.RE
.sp
prints all lines containing 
.IR string .
Regular expressions are also
used by the 
.I `s'
command for selecting old text to be replaced with new.

In addition to a specifying string literals, regular expressions can 
represent
classes of strings.  Strings thus represented are said to be matched
by the corresponding regular expression.  
If it is possible for a regular expression
to match several strings in a line, then the left-most longest match is
the one selected.

The following symbols are used in constructing regular expressions:

.TP 8
c
Any character 
.I c
not listed below, including `{', '}', `(', `)', `<' and `>',
matches itself.

.TP 8
\fR\\\fIc\fR
Any backslash-escaped character 
.IR c ,
except for `{', '}', `(', `)', `<' and `>',
matches itself. 

.TP 8
\fR.\fR
Matches any single character.

.TP 8
.I [char-class]
Matches any single character in 
.IR char-class .
To include a  `]'
in
.IR char-class ,
it must be the first character.
A range of characters may be specified by separating the end characters
of the range with a `-', e.g., `a-z' specifies the lower case characters.
If `-' appears as the first or last
character of 
.IR char-class , 
then it matches itself.
All other characters in
.I char-class
match themselves.

.TP 8
[^\fIchar-class\fR]
Matches any single character, other than newline, not in
.IR char-class .
.IR char-class
is defined 
as above.

.TP 8
^
If `^' is the first character of a regular expression, then it
anchors the regular expression to the beginning of a line.
Otherwise, it matches itself.

.TP 8
$
If `$' is the last character of a regular expression, it
anchors the regular expression to the end of a line.
Otherwise, it matches itself.

.TP 8
\fR\\<\fR
Anchors the single character regular expression or subexpression 
immediately following it to the beginning of a word. 
(This may not be available)

.TP 8
\fR\\>\fR
Anchors the single character regular expression or subexpression 
immediately following it to the end of a word. 
(This may not be available)

.TP 8
\fR\\(\fIre\fR\\)\fR
Defines a subexpression
.IR re .
Subexpressions may be nested. 
A subsequent backreference of the form \fI`\\n'\fR, where
.I n
is a number in the range [1,9], expands to the text matched by the
.IR n th
subexpression.   
For example, the regular expression `\\(.*\\)\\1' matches any string
consisting of identical adjacent substrings.
Subexpressions are ordered relative to
their left delimiter.

.TP 8
*
Matches the single character regular expression or subexpression
immediately preceding it zero or more times.

.TP 8
\fR\\{\fIn,m\fR\\}\fR or \fR\\{\fIn,\fR\\}\fR or \fR\\{\fIn\fR\\}\fR
Matches the single character regular expression or subexpression
immediately preceding it at least
.I n
and at most
.I m
times.
If
.I m
is omitted, then it matches at least 
.I n 
times.
If the comma is also omitted, then it matches exactly 
.I n 
times.

.SS COMMANDS
All
.B ed
commands are single characters, though some require additonal parameters.
If a command's paramters extend over several lines, then
each line except for the last
must end in a backslash (\\).

In general, at most one command is allowed per line.
However, most commands accept a print suffix, which is any of
.I `p'
(print),
.I `l'
(list) ,
or
.I `n'
(enumerate),
to print the last line affected by the command.

An interrupt (typically ^C) has the effect of aborting the current command
and returning the editor to command mode.

.B ed
recognizes the following commands.  The commands are shown together with
the default address or address range supplied if none is
specified (in parenthesis). 

.TP 8
(.)a
Appends text to the buffer after the addressed line.
Text is entered in input mode.
The current address is set to last line entered.

.TP 8
(.,.)c
Changes lines in the buffer.  The addressed lines are deleted
from the buffer, and text is appended in their place.
Text is entered in input mode.
The current address is set to last line entered.

.TP 8
(.,.)d
Deletes the addressed lines from the buffer.
If there is a line after the deleted range, then the current address is set 
to this line. Otherwise the current address is set to the line
before the deleted range.

.TP 8
.RI e \ file
Edits
.IR file ,
and sets the default filename.
If
.I file 
is not specified, then the  default filename is used.
Any lines in the buffer are deleted before
the new file is read.
The current address is set to the last line read.

.TP 8
.RI e \ !command
Edits the standard output of
.I command 
executed via
.IR sh (1).
The default filename is unchanged.
Any lines in the buffer are deleted before the output of
.I command
is read.
The current address is set to the last line read.

.TP 8
.RI E \ name
Edits
.I name
unconditionally.  
This is similar to the
.I e
command,
except that unwritten changes are discarded without warning.
The current address is set to the last line read.

.TP 8
.RI f \ name
Sets the default filename to 
.IR name .
If 
.I name
is not specified, then the default unescaped filename is printed.
If 
.I name 
is  prefixed with a bang (!), then 
it is executed as a command via 
.IR sh (1),
in subsequent reads and writes.

.TP 8
.RI (1,$)g /re/command-list
Applies
.I command-list
to each of the addressed lines matching a regular expression
.IR re .
The current address is set to the
line currently matched before
.I command-list
is executed.
At the end of the
.I `g'
command, the current address is set to the last line affected by
.IR command-list .

Each command in 
.I command-list
must be on a separate line,
and every line except for the last must be terminated by a backslash
(\\).
Any commands are allowed, except for
.IR `g' ,
.IR `G' ,
.IR `v' ,
and
.IR `V' .

.TP 8
.RI (1,$)G /re/
Interactively edits the addressed lines matching a regular expression
.IR re.
For each matching line,
the line is printed,
the current address is set,
and the user is prompted to enter a command list.
At the end of the
.I `G'
command, the current address
is set to the last line affected by the command
list.

The format of the command list is the same as that of the
.I `g'
command.  A newline alone acts as a null command list. 
A single `&' repeats the last non-null command list.

.TP 8
H
Toggles the printing of error explanations.
By default, explanations are not printed.
It is recommended that ed scripts begin with this command to
aid in debugging.

.TP 8
h
Prints an explanation of the last error.

.TP 8
(.)i
Inserts text in the buffer before the current line.
Text is entered in input mode.
The current address is set to the last line entered.

.TP 8
(.,.+1)j
Joins the addressed lines.  The addressed lines are
deleted from the buffer and replaced by a single
line containing their joined text.
The current address is set to the resultant line.

.TP 8
.RI (.)k lc
Marks a line with a lower case letter
.IR lc .  
The  line can then be addressed as
.I `'lc'
(i.e., a single quote followed by
.I lc
) in subsequent commands.  The mark is not cleared until the line is
deleted or otherwise modified.

.TP 8
(.,.)l
Prints the addressed lines unambiguously. 
The current address is set to the last line
printed.  

.TP 8
(.,.)m(.)
Moves lines in the buffer.  The addressed lines are moved to after the
right-hand destination address, which may be the address
.IR `0'
(zero).
The current address is set to the
last line moved.

.TP 8
(.,.)n
Prints the addressed lines along with
their line numbers.  The current address is set to the last line
printed.

.TP 8
(.,.)p
Prints the addressed lines. The current address is set to the last line
printed.  

.TP 8
P
Toggles the command prompt on and off.
Unless a prompt was specified by with command-line option
\fI-p string\fR, the command prompt is by default turned off.

.TP 8
q
Quits ed.  

.TP 8
Q
Quits ed unconditionally.
This is similar to the
.I q
command,
except that unwritten changes are discarded without warning.

.TP 8
.RI ($)r \ file
Reads
.I file
to after the addressed line.  If 
.I file
is not specified, then the default
filename is used.  If there was no default filename prior to the command,
then the default filename is set to
.IR file .
Otherwise, the default filename is unchanged.  
The current address is set to the last line read.

.TP 8
.RI ($)r \ !command
Reads the standard output of
.I command
executed via
.IR sh (1)
to after the addressed line.
The default filename is unchanged.
The current address is set to the last line read.

.TP 8
.RI (.,.)s /re/replacement/[gn]
Replaces text in the addressed lines 
matching a regular expression
.I re
with 
.IR replacement .
By default, only the first match in each line is replaced.
The 
.I `g'
(global) suffix causes every match to be replaced.
The
.I `n'
suffix, where
.I n
is a postive number, causes only the
.IR n th
match to be replaced.
The current address is set the last line affected.

An unescaped `&' in
.I replacement
is replaced by the currently matched text.
The character sequence
\fI`\\m'\fR,
where
.I m
is a number in the range [1,9], is replaced by the
.IR m th
backreference expression of the matched text.
If 
.I replacement
consists of a single `%', then
.I replacement 
from the last substitution is used.
Newlines may be included in 
.I replacement
if they are escaped with a backslash (\\).

.I re
and 
.I replacement
may be delimited by any character other than space and newline.
If one or two of the last delimiters is omitted, then the affected lines
are printed as though the print suffix
.I `p' 
were specified.

.TP 8
.RI (.,.)s [rgp]*
Repeats the last substitution.
This form of the
.I `s'
command may be suffixed with
any combination of the characters
.IR `r' ,
.IR `g' ,
and
.IR `p' .
The 
.I `r'
suffix causes
the regular expression of the last search to be used instead of the
that of the last substitution.
The
.I `g'
suffix toggles the global suffix of the last substitution.
The
.I `p'
suffix toggles the print suffix of the last substitution
The current address is set to the last line affected.

.TP 8
(.,.)t(.)
Copies (i.e., transfers) the addressed lines to after the right-hand
destination address, which may be the address
.IR `0'
(zero).
The current address is set to the last line
copied.

.TP 8
u
Undoes the last command.  
The global commands 
.IR `g' ,
.IR `G' ,
.IR `v' ,
and
.IR `V' .
are treated as a single command by undo.
.I `u'
is its own inverse.

.TP 8
.RI (1,$)v /pat/command-list
Applies
.I command-list
to each of the addressed lines not matching a regular expression
.IR re .
This is similar to the
.I `g'
command.

.TP 8
.RI (1,$)V /re/
Interactively edits the addressed lines not matching a regular expression
.IR re.
This is similar to the
.I `G'
command.

.TP 8
.RI (1,$)w \ file
Writes the addressed lines to
.IR file .
Any previous contents of
.I file
is lost without warning.
If there is no default filename, then the default filename is set to
.IR file,
otherwise it is unchanged.  If no filename is specified, then the default
filename is used.
The current address is unchanged.

.TP 8
.RI (1,$)wq \ file
Writes the addressed lines to
.IR file ,
and then executes a
.I `q'
command.

.TP 8
.RI (1,$)w \ !command
Writes the addressed lines to the standard input of
.I command
executed via
.IR sh (1).
The default filename and current address are unchanged.

.TP 8
.RI (1,$)W \ file
Appends the addressed lines to the end of
.IR file .
This is similar to the
.I `w'
command, expect that the previous contents of file is not clobbered.
The current address is unchanged.

.TP 8
x
Prompts for an encryption key which is used in subsequent reads and
writes.  If a newline alone is entered as the key, then encryption is
turned off.  Otherwise, echoing is disabled while a key is read.
Encryption/decryption is done using the bdes(1) algorithm.

.TP 8
.RI (.+1)z n
Scrolls
.I n
lines at a time starting at addressed line.  If
.I n
is not specified, then the current window size is used.
The current address is set to the last line printed.

.TP 8
!command
Runs 
.I command
via
.IR sh (1).
If the first character of
.I command 
is `!', then it is replaced by text of the
previous
.IR !command .
.B ed
does not process
.I command
for backslash (\\) escapes.
However, an unescaped
.I `%'
is replaced by the default file name.
When the shell returns from execution, a `!'
is printed to the standard output.
The current line is unchanged.

.TP 8
($)=
Prints the line number of the addressed line.

.TP 8
(.+1)newline
Prints the addressed line, and sets the current address to
that line.

.SH FILES
.TP 20
/tmp/ed.*
Buffer file
.TP 20
\fR./ed.hup\fR, $HOME/ed.hup
First and second files to which 
.B ed
attempts to write the  buffer if the terminal hangs up.

.SH SEE ALSO

.IR vi (1),
.IR sed (1),
.IR regex (3),
.IR bdes (1),
.IR sh (1).

USD:12-13

B. W. Kernighan and P. J. Plauger,
.I Software Tools in Pascal ,
Addison-Wesley, 1981.

.SH LIMITATIONS
.B ed
processes
.I file
arguments for backslash escapes, i.e.,  in a filename,
any characters preceded by a backslash (\\) are
interpreted literally.

When reading a file into the editor buffer, ASCII NUL characters are
discarded, and long lines are split by insertion of a newline.
If the file is not terminated by a newline, then one is appended.
.B ed
prints a diagnostic indicating any modifications.

maximum line length: 4096 chars

per line overhead: 4 ints

.SH DIAGNOSTICS
When an error occurs,
.B ed
prints a `?' and returns to command mode.
An explanation of the last error can be 
printed with the 
.I `h'
command.

Attempting to quit
.B ed
or edit another file before writing a modified buffer
results in an error.
If the command is entered a second time, it succeeds,
but any changes to buffer are lost.