The
utility is a line-oriented text editor.
It is used to create, display, modify and otherwise manipulate text
files.
When invoked as
red
the editor runs in
Qq restricted
mode, in which the only difference is that the editor restricts the
use of filenames which start with
`!'
(interpreted as shell commands by
)
or contain a
`/'
Note that editing outside of the current directory is only prohibited
if the user does not have write access to the current directory.
If a user has write access to the current directory, then symbolic
links can be created in the current directory, in which case
red
will not stop the user from editing the file that the symbolic link
points to.
If invoked with a
file
argument, then a copy of
file
is read into the editor's buffer.
Changes are made to this copy and not directly to
file
itself.
Upon quitting
,
any changes not explicitly saved with a
w
command are lost.
Editing is done in two distinct modes:
command
and
input
When first invoked,
is in command mode.
In this mode commands are read from the standard input and
executed to manipulate the contents of the editor buffer.
A typical command might look like:
,s / old
/ new/ g
which replaces all occurrences of the string
old
with
new
When an input command, such as
a
(append),
i
(insert) or
c
(change), is given,
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.
Lines consist of text up to and
including a
newline
character.
Input mode is terminated by
entering a single period
(.
)
on a line.
All
commands operate on whole lines or ranges of lines; e.g.,
the
d
command deletes lines; the
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
s
command is applied to whole lines at a time.
In general,
commands consist of zero or more line addresses, followed by a single
character command and possibly additional parameters; i.e.,
commands have the structure:
[address [, address
]
]
command [parameters
]
The address(es) indicate the line or range of lines to be affected by the
command.
If fewer addresses are given than the command accepts, then
default addresses are supplied.
OPTIONS
The following options are available:
-s
Suppress diagnostics.
This should be used if
's
standard input is from a script.
-x
Prompt for an encryption key to be used in subsequent reads and writes
(see the
x
command).
-p string
Specify a command prompt.
This may be toggled on and off with the
P
command.
file
Specify the name of a file to read.
If
file
is prefixed with a
bang (!), then it is interpreted as a shell command.
In this case,
what is read is
the standard output of
file
executed via
sh(1).
To read a file whose name begins with a bang, prefix the
name with a backslash (\).
The default filename is set to
file
only if it is not prefixed with a bang.
LINE ADDRESSING
An address represents the number of a line in the buffer.
The
utility maintains a
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.,
+-
and
^
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
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 second.
If only one address is given in a range, then
the second address is set to the given address.
If an
n -tuple
of addresses is given where
n > 2
then the corresponding range is determined by the last two addresses in
the
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:
.
The current line (address) in the buffer.
$
The last line in the buffer.
n
The
n th,
line in the buffer
where
n
is a number in the range
[0,$]
- or
The previous line.
This is equivalent to
-1
and may be repeated with cumulative effect.
-n or ^n
The
n th
previous line, where
n
is a non-negative number.
+
The next line.
This is equivalent to
+1
and may be repeated with cumulative effect.
+n
The
n th
next line, where
n
is a non-negative number.
, or
The first through last lines in the buffer.
This is equivalent to
the address range
1,$
;
The current through last lines in the buffer.
This is equivalent to
the address range
.,$
/re/
The next line containing the regular expression
re
The search wraps to the beginning of the buffer and continues down to the
current line, if necessary.
// repeats the last search.
?re?
The
previous line containing the regular expression
re
The search wraps to the end of the buffer and continues up to the
current line, if necessary.
?? repeats the last search.
'lc
The
line previously marked by a
k
(mark) command, where
lc
is a lower case letter.
REGULAR EXPRESSIONS
Regular expressions are patterns used in selecting text.
For example, the command:
g / string
/
prints all lines containing
string
Regular expressions are also
used by the
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:
c
Any character
c
not listed below, including
`{'
,
`}'
,
`('
,
`)'
,
`<'
and
`>'
,
matches itself.
\ c
Any backslash-escaped character
c
except for
`{'
,
`}'
,
`('
,
`)'
,
`<'
and
`>'
,
matches itself.
.
Match any single character.
[char-class]
Match any single character in
char-class
To include a
`]'
in
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.
The following literal expressions can also be used in
char-class
to specify sets of characters:
[:alnum:] Ta [:cntrl:] Ta [:lower:] Ta [:space:]
[:alpha:] Ta [:digit:] Ta [:print:] Ta [:upper:]
[:blank:] Ta [:graph:] Ta [:punct:] Ta [:xdigit:]
If
`-'
appears as the first or last
character of
char-class
then it matches itself.
All other characters in
char-class
match themselves.
Patterns in
char-class
of the form:
[. col-elm .
]
or,
[= col-elm =
]
where
col-elm
is a
collating element
are interpreted according to the current locale settings
(not currently supported).
See
regex(3)
and
re_format7
for an explanation of these constructs.
[^char-class]
Match any single character, other than newline, not in
char-classChar-class
is defined
as above.
^
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.
$
If
$
is the last character of a regular expression, it
anchors the regular expression to the end of a line.
Otherwise, it matches itself.
\
Anchor the single character regular expression or subexpression
immediately following it to the beginning of a word.
(This may not be available)
\
Anchor the single character regular expression or subexpression
immediately following it to the end of a word.
(This may not be available)
\ (re\)
Define a subexpression
re
Subexpressions may be nested.
A subsequent backreference of the form
\ n
where
n
is a number in the range [1,9], expands to the text matched by the
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.
*
Match the single character regular expression or subexpression
immediately preceding it zero or more times.
If
*
is the first
character of a regular expression or subexpression, then it matches
itself.
The
*
operator sometimes yields unexpected results.
For example, the regular expression
`b*'
matches the beginning of
the string
`abbb'
(as opposed to the substring
`bbb'
) ,
since a null match
is the only left-most match.
\{n,m\} or \{n,\} or \{n\}
Match the single character regular expression or subexpression
immediately preceding it at least
n
and at most
m
times.
If
m
is omitted, then it matches at least
n
times.
If the comma is also omitted, then it matches exactly
n
times.
Additional regular expression operators may be defined depending on the
particular
regex(3)
implementation.
COMMANDS
All
commands are single characters, though some require additional parameters.
If a command's parameters extend over several lines, then
each line except for the last
must be terminated with a backslash (\).
In general, at most one command is allowed per line.
However, most commands accept a print suffix, which is any of
p
(print),
l
(list),
or
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.
The
utility
recognizes the following commands.
The commands are shown together with
the default address or address range supplied if none is
specified (in parenthesis).
(.)a
Append text to the buffer after the addressed line.
Text is entered in input mode.
The current address is set to last line entered.
(.,.)c
Change 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.
(.,.)d
Delete 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.
e file
Edit
file
and sets the default filename.
If
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.
e !command
Edit the standard output of
!command
(see
!command
below).
The default filename is unchanged.
Any lines in the buffer are deleted before the output of
command
is read.
The current address is set to the last line read.
E file
Edit
file
unconditionally.
This is similar to the
e
command,
except that unwritten changes are discarded without warning.
The current address is set to the last line read.
f file
Set the default filename to
file
If
file
is not specified, then the default unescaped filename is printed.
(1,$)g/re/command-list
Apply
command-list
to each of the addressed lines matching a regular expression
re
The current address is set to the
line currently matched before
command-list
is executed.
At the end of the
g
command, the current address is set to the last line affected by
command-list
Each command in
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
gGv
and
V
A newline alone in
command-list
is equivalent to a
p
command.
(1,$)G/re/
Interactively edit the addressed lines matching a regular expression
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
G
command, the current address
is set to the last line affected by (the last)
command-list
The format of
command-list
is the same as that of the
g
command.
A newline alone acts as a null command list.
A single
`&'
repeats the last non-null command list.
H
Toggle 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.
h
Print an explanation of the last error.
(.)i
Insert text in the buffer before the current line.
Text is entered in input mode.
The current address is set to the last line entered.
(.,.+1)j
Join 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.
(.)klc
Mark a line with a lower case letter
lc
The line can then be addressed as
'lc
(i.e., a single quote followed by
lc
in subsequent commands.
The mark is not cleared until the line is
deleted or otherwise modified.
(.,.)l
Print the addressed lines unambiguously.
If a single line fills for than one screen (as might be the case
when viewing a binary file, for instance), a
``--More--
''
prompt is printed on the last line.
The
utility waits until the RETURN key is pressed
before displaying the next screen.
The current address is set to the last line
printed.
(.,.)m(.)
Move lines in the buffer.
The addressed lines are moved to after the
right-hand destination address, which may be the address
0
(zero).
The current address is set to the
last line moved.
(.,.)n
Print the addressed lines along with
their line numbers.
The current address is set to the last line
printed.
(.,.)p
Print the addressed lines.
The current address is set to the last line
printed.
P
Toggle the command prompt on and off.
Unless a prompt was specified by with command-line option
-p string
the command prompt is by default turned off.
q
Quit
.
Q
Quit
unconditionally.
This is similar to the
q
command,
except that unwritten changes are discarded without warning.
($)r file
Read
file
to after the addressed line.
If
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
file
Otherwise, the default filename is unchanged.
The current address is set to the last line read.
($)r !command
Read
to after the addressed line
the standard output of
!command
(see the
!command
below).
The default filename is unchanged.
The current address is set to the last line read.
(.,.)s/re/replacement/
(.,.)s/re/replacement/g
(.,.)s/re/replacement/n
Replace text in the addressed lines
matching a regular expression
re
with
replacement
By default, only the first match in each line is replaced.
If the
g
(global) suffix is given, then every match to be replaced.
The
n
suffix, where
n
is a positive number, causes only the
n th
match to be replaced.
It is an error if no substitutions are performed on any of the addressed
lines.
The current address is set the last line affected.
and
replacement
may be delimited by any character other than space and newline
(see the
s
command below).
If one or two of the last delimiters is omitted, then the last line
affected is printed as though the print suffix
p
were specified.
An unescaped
`&'
in
replacement
is replaced by the currently matched text.
The character sequence
\m
where
m
is a number in the range [1,9], is replaced by the
m th
backreference expression of the matched text.
If
replacement
consists of a single
`%'
,
then
replacement
from the last substitution is used.
Newlines may be embedded in
replacement
if they are escaped with a backslash (\).
(.,.)s
Repeat the last substitution.
This form of the
s
command accepts a count suffix
n
or any combination of the characters
rg
and
p
If a count suffix
n
is given, then only the
n th
match is replaced.
The
r
suffix causes
the regular expression of the last search to be used instead of the
that of the last substitution.
The
g
suffix toggles the global suffix of the last substitution.
The
p
suffix toggles the print suffix of the last substitution
The current address is set to the last line affected.
(.,.)t(.)
Copy (i.e., transfer) the addressed lines to after the right-hand
destination address, which may be the address
0
(zero).
The current address is set to the last line
copied.
u
Undo the last command and restores the current address
to what it was before the command.
The global commands
gGv
and
V
are treated as a single command by undo.
u
is its own inverse.
(1,$)v/re/command-list
Apply
command-list
to each of the addressed lines not matching a regular expression
re
This is similar to the
g
command.
(1,$)V/re/
Interactively edit the addressed lines not matching a regular expression
re
This is similar to the
G
command.
(1,$)w Ar file
Write the addressed lines to
file
Any previous contents of
file
is lost without warning.
If there is no default filename, then the default filename is set to
file
otherwise it is unchanged.
If no filename is specified, then the default
filename is used.
The current address is unchanged.
(1,$)wq Ar file
Write the addressed lines to
file
and then executes a
q
command.
(1,$)w Ar !command
Write the addressed lines to the standard input of
!command
(see the
!command
below).
The default filename and current address are unchanged.
(1,$)W Ar file
Append the addressed lines to the end of
file
This is similar to the
w
command, expect that the previous contents of file is not clobbered.
The current address is unchanged.
x
Prompt 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.
Pf (.+1)z n
Scroll
n
lines at a time starting at addressed line.
If
n
is not specified, then the current window size is used.
The current address is set to the last line printed.
!command
Execute
command
via
sh(1).
If the first character of
command
is
`!'
,
then it is replaced by text of the
previous
!command
The
utility does not process
command
for backslash (\) escapes.
However, an unescaped
%
is replaced by the default filename.
When the shell returns from execution, a
`!'
is printed to the standard output.
The current line is unchanged.
($)=
Print the line number of the addressed line.
(.+1)newline
Print the addressed line, and sets the current address to
that line.
FILES
/tmp/ed.*
buffer file
ed.hup
the file to which
attempts to write the buffer if the terminal hangs up
DIAGNOSTICS
When an error occurs,
prints a
`?'
and either returns to command mode
or exits if its input is from a script.
An explanation of the last error can be
printed with the
h
(help) command.
Since the
g
(global) command masks any errors from failed searches and substitutions,
it can be used to perform conditional operations in scripts; e.g.,
g / old
/ s// new/
replaces any occurrences of
old
with
new
If the
u
(undo) command occurs in a global command list, then
the command list is executed only once.
If diagnostics are not disabled, attempting to quit
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 the buffer are lost.
B. W. Kernighan
P. J. Plauger
Software Tools in Pascal
Addison-Wesley
1981
LIMITATIONS
The
utility processes
file
arguments for backslash escapes, i.e., in a filename,
any characters preceded by a backslash (\) are
interpreted literally.
If a text (non-binary) file is not terminated by a newline character,
then
appends one on reading/writing it.
In the case of a binary file,
does not append a newline on reading/writing.
per line overhead: 4 ints
HISTORY
An
command appeared in
Version 1 AT&T UNIX.
BUGS
The
utility does not recognize multibyte characters.
