The ed utility shall operate on a copy of the file it is editing;
changes made to the copy shall have no effect on the file until a
w (write) command is given. The copy of the text is called the
buffer.
Commands to ed have a simple and regular structure: zero, one, or
two addresses followed by a single-character command, possibly
followed by parameters to that command. These addresses specify
one or more lines in the buffer. Every command that requires
addresses has default addresses, so that the addresses very often
can be omitted. If the -p option is specified, the prompt string
shall be written to standard output before each command is read.
In general, only one command can appear on a line. Certain
commands allow text to be input. 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 shall be
recognized; all input is merely collected. Input mode is
terminated by entering a line consisting of two characters: a
<period> ('.') followed by a <newline>. This line is not
considered part of the input text.
Regular Expressions in ed
The ed utility shall support basic regular expressions, as
described in the Base Definitions volume of POSIX.1‐2017, Section
9.3, Basic Regular Expressions. Since regular expressions in ed
are always matched against single lines (excluding the
terminating <newline> characters), never against any larger
section of text, there is no way for a regular expression to
match a <newline>.
A null RE shall be equivalent to the last RE encountered.
Regular expressions are used in addresses to specify lines, and
in some commands (for example, the s substitute command) to
specify portions of a line to be substituted.
Addresses in ed
Addressing in ed relates to the current line. Generally, the
current line is the last line affected by a command. The current
line number is the address of the current line. If the edit
buffer is not empty, the initial value for the current line shall
be the last line in the edit buffer; otherwise, zero.
Addresses shall be constructed as follows:
1. The <period> character ('.') shall address the current line.
2. The <dollar-sign> character ('$') shall address the last line
of the edit buffer.
3. The positive decimal number n shall address the nth line of
the edit buffer.
4. The <apostrophe>-x character pair ("'x") shall address the
line marked with the mark name character x, which shall be a
lowercase letter from the portable character set. It shall be
an error if the character has not been set to mark a line or
if the line that was marked is not currently present in the
edit buffer.
5. A BRE enclosed by <slash> characters ('/') shall address the
first line found by searching forwards from the line
following the current line toward the end of the edit buffer
and stopping at the first line for which the line excluding
the terminating <newline> matches the BRE. The BRE consisting
of a null BRE delimited by a pair of <slash> characters shall
address the next line for which the line excluding the
terminating <newline> matches the last BRE encountered. In
addition, the second <slash> can be omitted at the end of a
command line. Within the BRE, a <backslash>-<slash> pair
("\/") shall represent a literal <slash> instead of the BRE
delimiter. If necessary, the search shall wrap around to the
beginning of the buffer and continue up to and including the
current line, so that the entire buffer is searched.
6. A BRE enclosed by <question-mark> characters ('?') shall
address the first line found by searching backwards from the
line preceding the current line toward the beginning of the
edit buffer and stopping at the first line for which the line
excluding the terminating <newline> matches the BRE. The BRE
consisting of a null BRE delimited by a pair of <question-
mark> characters ("??") shall address the previous line for
which the line excluding the terminating <newline> matches
the last BRE encountered. In addition, the second <question-
mark> can be omitted at the end of a command line. Within the
BRE, a <backslash>-<question-mark> pair ("\?") shall
represent a literal <question-mark> instead of the BRE
delimiter. If necessary, the search shall wrap around to the
end of the buffer and continue up to and including the
current line, so that the entire buffer is searched.
7. A <plus-sign> ('+') or <hyphen-minus> character ('-')
followed by a decimal number shall address the current line
plus or minus the number. A <plus-sign> or <hyphen-minus>
character not followed by a decimal number shall address the
current line plus or minus 1.
Addresses can be followed by zero or more address offsets,
optionally <blank>-separated. Address offsets are constructed as
follows:
* A <plus-sign> or <hyphen-minus> character followed by a
decimal number shall add or subtract, respectively, the
indicated number of lines to or from the address. A <plus-
sign> or <hyphen-minus> character not followed by a decimal
number shall add or subtract 1 to or from the address.
* A decimal number shall add the indicated number of lines to
the address.
It shall not be an error for an intermediate address value to be
less than zero or greater than the last line in the edit buffer.
It shall be an error for the final address value to be less than
zero or greater than the last line in the edit buffer. It shall
be an error if a search for a BRE fails to find a matching line.
Commands accept zero, one, or two addresses. If more than the
required number of addresses are provided to a command that
requires zero addresses, it shall be an error. Otherwise, if more
than the required number of addresses are provided to a command,
the addresses specified first shall be evaluated and then
discarded until the maximum number of valid addresses remain, for
the specified command.
Addresses shall be separated from each other by a <comma> (',')
or <semicolon> character (';'). In the case of a <semicolon>
separator, the current line ('.') shall be set to the first
address, and only then will the second address be calculated.
This feature can be used to determine the starting line for
forwards and backwards searches; see rules 5. and 6.
Addresses can be omitted on either side of the <comma> or
<semicolon> separator, in which case the resulting address pairs
shall be as follows:
┌──────────┬─────────────┐
│Specified │ Resulting │
├──────────┼─────────────┤
│, │ 1 , $ │
│, addr │ 1 , addr │
│addr , │ addr , addr │
│; │ . ; $ │
│; addr │ . ; addr │
│addr ; │ addr ; addr │
└──────────┴─────────────┘
Any <blank> characters included between addresses, address
separators, or address offsets shall be ignored.
Commands in ed
In the following list of ed commands, the default addresses are
shown in parentheses. The number of addresses shown in the
default shall be the number expected by the command. The
parentheses are not part of the address; they show that the given
addresses are the default.
It is generally invalid for more than one command to appear on a
line. However, any command (except e, E, f, q, Q, r, w, and !)
can be suffixed by the letter l, n, or p; in which case, except
for the l, n, and p commands, the command shall be executed and
then the new current line shall be written as described below
under the l, n, and p commands. When an l, n, or p suffix is used
with an l, n, or p command, the command shall write to standard
output as described below, but it is unspecified whether the
suffix writes the current line again in the requested format or
whether the suffix has no effect. For example, the pl command
(base p command with an l suffix) shall either write just the
current line or write it twice—once as specified for p and once
as specified for l. Also, the g, G, v, and V commands shall take
a command as a parameter.
Each address component can be preceded by zero or more <blank>
characters. The command letter can be preceded by zero or more
<blank> characters. If a suffix letter (l, n, or p) is given, the
application shall ensure that it immediately follows the command.
The e, E, f, r, and w commands shall take an optional file
parameter, separated from the command letter by one or more
<blank> characters.
If changes have been made in the buffer since the last w command
that wrote the entire buffer, ed shall warn the user if an
attempt is made to destroy the editor buffer via the e or q
commands. The ed utility shall write the string:
"?\n"
(followed by an explanatory message if help mode has been enabled
via the H command) to standard output and shall continue in
command mode with the current line number unchanged. If the e or
q command is repeated with no intervening command, it shall take
effect.
If a terminal disconnect (see the Base Definitions volume of
POSIX.1‐2017, Chapter 11, General Terminal Interface, Modem
Disconnect and Closing a Device Terminal), is detected:
* If accompanied by a SIGHUP signal, the ed utility shall
operate as described in the ASYNCHRONOUS EVENTS section for a
SIGHUP signal.
* If not accompanied by a SIGHUP signal, the ed utility shall
act as if an end-of-file had been detected on standard input.
If an end-of-file is detected on standard input:
* If the ed utility is in input mode, ed shall terminate input
mode and return to command mode. It is unspecified if any
partially entered lines (that is, input text without a
terminating <newline>) are discarded from the input text.
* If the ed utility is in command mode, it shall act as if a q
command had been entered.
If the closing delimiter of an RE or of a replacement string (for
example, '/') in a g, G, s, v, or V command would be the last
character before a <newline>, that delimiter can be omitted, in
which case the addressed line shall be written. For example, the
following pairs of commands are equivalent:
s/s1/s2 s/s1/s2/p
g/s1 g/s1/p
?s1 ?s1?
If an invalid command is entered, ed shall write the string:
"?\n"
(followed by an explanatory message if help mode has been enabled
via the H command) to standard output and shall continue in
command mode with the current line number unchanged.
Append Command
Synopsis:
(.)a
<text>
.
The a command shall read the given text and append it after the
addressed line; the current line number shall become the address
of the last inserted line or, if there were none, the addressed
line. Address 0 shall be valid for this command; it shall cause
the appended text to be placed at the beginning of the buffer.
Change Command
Synopsis:
(.,.)c
<text>
.
The c command shall delete the addressed lines, then accept input
text that replaces these lines; the current line shall be set to
the address of the last line input; or, if there were none, at
the line after the last line deleted; if the lines deleted were
originally at the end of the buffer, the current line number
shall be set to the address of the new last line; if no lines
remain in the buffer, the current line number shall be set to
zero. Address 0 shall be valid for this command; it shall be
interpreted as if address 1 were specified.
Delete Command
Synopsis:
(.,.)d
The d command shall delete the addressed lines from the buffer.
The address of the line after the last line deleted shall become
the current line number; if the lines deleted were originally at
the end of the buffer, the current line number shall be set to
the address of the new last line; if no lines remain in the
buffer, the current line number shall be set to zero.
Edit Command
Synopsis:
e [file]
The e command shall delete the entire contents of the buffer and
then read in the file named by the pathname file. The current
line number shall be set to the address of the last line of the
buffer. If no pathname is given, the currently remembered
pathname, if any, shall be used (see the f command). The number
of bytes read shall be written to standard output, unless the -s
option was specified, in the following format:
"%d\n", <number of bytes read>
The name file shall be remembered for possible use as a default
pathname in subsequent e, E, r, and w commands. If file is
replaced by '!', the rest of the line shall be taken to be a
shell command line whose output is to be read. Such a shell
command line shall not be remembered as the current file. All
marks shall be discarded upon the completion of a successful e
command. If the buffer has changed since the last time the entire
buffer was written, the user shall be warned, as described
previously.
Edit Without Checking Command
Synopsis:
E [file]
The E command shall possess all properties and restrictions of
the e command except that the editor shall not check to see
whether any changes have been made to the buffer since the last w
command.
Filename Command
Synopsis:
f [file]
If file is given, the f command shall change the currently
remembered pathname to file; whether the name is changed or not,
it shall then write the (possibly new) currently remembered
pathname to the standard output in the following format:
"%s\n", <pathname>
The current line number shall be unchanged.
Global Command
Synopsis:
(1,$)g/RE/command list
In the g command, the first step shall be to mark every line for
which the line excluding the terminating <newline> matches the
given RE. Then, going sequentially from the beginning of the file
to the end of the file, the given command list shall be executed
for each marked line, with the current line number set to the
address of that line. Any line modified by the command list shall
be unmarked. When the g command completes, the current line
number shall have the value assigned by the last command in the
command list. If there were no matching lines, the current line
number shall not be changed. A single command or the first of a
list of commands shall appear on the same line as the global
command. All lines of a multi-line list except the last line
shall be ended with a <backslash> preceding the terminating
<newline>; the a, i, and c commands and associated input are
permitted. The '.' terminating input mode can be omitted if it
would be the last line of the command list. An empty command list
shall be equivalent to the p command. The use of the g, G, v, V,
and ! commands in the command list produces undefined results.
Any character other than <space> or <newline> can be used instead
of a <slash> to delimit the RE. Within the RE, the RE delimiter
itself can be used as a literal character if it is preceded by a
<backslash>.
Interactive Global Command
Synopsis:
(1,$)G/RE/
In the G command, the first step shall be to mark every line for
which the line excluding the terminating <newline> matches the
given RE. Then, for every such line, that line shall be written,
the current line number shall be set to the address of that line,
and any one command (other than one of the a, c, i, g, G, v, and
V commands) shall be read and executed. A <newline> shall act as
a null command (causing no action to be taken on the current
line); an '&' shall cause the re-execution of the most recent
non-null command executed within the current invocation of G.
Note that the commands input as part of the execution of the G
command can address and affect any lines in the buffer. Any line
modified by the command shall be unmarked. The final value of the
current line number shall be the value set by the last command
successfully executed. (Note that the last command successfully
executed shall be the G command itself if a command fails or the
null command is specified.) If there were no matching lines, the
current line number shall not be changed. The G command can be
terminated by a SIGINT signal. Any character other than <space>
or <newline> can be used instead of a <slash> to delimit the RE
and the replacement. Within the RE, the RE delimiter itself can
be used as a literal character if it is preceded by a
<backslash>.
Help Command
Synopsis:
h
The h command shall write a short message to standard output that
explains the reason for the most recent '?' notification. The
current line number shall be unchanged.
Help-Mode Command
Synopsis:
H
The H command shall cause ed to enter a mode in which help
messages (see the h command) shall be written to standard output
for all subsequent '?' notifications. The H command alternately
shall turn this mode on and off; it is initially off. If the
help-mode is being turned on, the H command also explains the
previous '?' notification, if there was one. The current line
number shall be unchanged.
Insert Command
Synopsis:
(.)i
<text>
.
The i command shall insert the given text before the addressed
line; the current line is set to the last inserted line or, if
there was none, to the addressed line. This command differs from
the a command only in the placement of the input text. Address 0
shall be valid for this command; it shall be interpreted as if
address 1 were specified.
Join Command
Synopsis:
(.,.+1)j
The j command shall join contiguous lines by removing the
appropriate <newline> characters. If exactly one address is
given, this command shall do nothing. If lines are joined, the
current line number shall be set to the address of the joined
line; otherwise, the current line number shall be unchanged.
Mark Command
Synopsis:
(.)kx
The k command shall mark the addressed line with name x, which
the application shall ensure is a lowercase letter from the
portable character set. The address "'x" shall then refer to this
line; the current line number shall be unchanged.
List Command
Synopsis:
(.,.)l
The l command shall write to standard output the addressed lines
in a visually unambiguous form. The characters listed in the Base
Definitions volume of POSIX.1‐2017, Table 5-1, Escape Sequences
and Associated Actions ('\\', '\a', '\b', '\f', '\r', '\t', '\v')
shall be written as the corresponding escape sequence; the '\n'
in that table is not applicable. Non-printable characters not in
the table shall be written as one three-digit octal number (with
a preceding <backslash> character) for each byte in the character
(most significant byte first).
Long lines shall be folded, with the point of folding indicated
by <newline> preceded by a <backslash>; the length at which
folding occurs is unspecified, but should be appropriate for the
output device. The end of each line shall be marked with a '$',
and '$' characters within the text shall be written with a
preceding <backslash>. An l command can be appended to any other
command other than e, E, f, q, Q, r, w, or !. The current line
number shall be set to the address of the last line written.
Move Command
Synopsis:
(.,.)maddress
The m command shall reposition the addressed lines after the line
addressed by address. Address 0 shall be valid for address and
cause the addressed lines to be moved to the beginning of the
buffer. It shall be an error if address address falls within the
range of moved lines. The current line number shall be set to the
address of the last line moved.
Number Command
Synopsis:
(.,.)n
The n command shall write to standard output the addressed lines,
preceding each line by its line number and a <tab>; the current
line number shall be set to the address of the last line written.
The n command can be appended to any command other than e, E, f,
q, Q, r, w, or !.
Print Command
Synopsis:
(.,.)p
The p command shall write to standard output the addressed lines;
the current line number shall be set to the address of the last
line written. The p command can be appended to any command other
than e, E, f, q, Q, r, w, or !.
Prompt Command
Synopsis:
P
The P command shall cause ed to prompt with an <asterisk> ('*')
(or string, if -p is specified) for all subsequent commands. The
P command alternatively shall turn this mode on and off; it shall
be initially on if the -p option is specified; otherwise, off.
The current line number shall be unchanged.
Quit Command
Synopsis:
q
The q command shall cause ed to exit. If the buffer has changed
since the last time the entire buffer was written, the user shall
be warned, as described previously.
Quit Without Checking Command
Synopsis:
Q
The Q command shall cause ed to exit without checking whether
changes have been made in the buffer since the last w command.
Read Command
Synopsis:
($)r [file]
The r command shall read in the file named by the pathname file
and append it after the addressed line. If no file argument is
given, the currently remembered pathname, if any, shall be used
(see the e and f commands). The currently remembered pathname
shall not be changed unless there is no remembered pathname.
Address 0 shall be valid for r and shall cause the file to be
read at the beginning of the buffer. If the read is successful,
and -s was not specified, the number of bytes read shall be
written to standard output in the following format:
"%d\n", <number of bytes read>
The current line number shall be set to the address of the last
line read in. If file is replaced by '!', the rest of the line
shall be taken to be a shell command line whose output is to be
read. Such a shell command line shall not be remembered as the
current pathname.
Substitute Command
Synopsis:
(.,.)s/RE/replacement/flags
The s command shall search each addressed line for an occurrence
of the specified RE and replace either the first or all (non-
overlapped) matched strings with the replacement; see the
following description of the g suffix. It is an error if the
substitution fails on every addressed line. Any character other
than <space> or <newline> can be used instead of a <slash> to
delimit the RE and the replacement. Within the RE, the RE
delimiter itself can be used as a literal character if it is
preceded by a <backslash>. The current line shall be set to the
address of the last line on which a substitution occurred.
An <ampersand> ('&') appearing in the replacement shall be
replaced by the string matching the RE on the current line. The
special meaning of '&' in this context can be suppressed by
preceding it by <backslash>. As a more general feature, the
characters '\n', where n is a digit, shall be replaced by the
text matched by the corresponding back-reference expression. If
the corresponding back-reference expression does not match, then
the characters '\n' shall be replaced by the empty string. When
the character '%' is the only character in the replacement, the
replacement used in the most recent substitute command shall be
used as the replacement in the current substitute command; if
there was no previous substitute command, the use of '%' in this
manner shall be an error. The '%' shall lose its special meaning
when it is in a replacement string of more than one character or
is preceded by a <backslash>. For each <backslash> encountered
in scanning replacement from beginning to end, the following
character shall lose its special meaning (if any). It is
unspecified what special meaning is given to any character other
than <backslash>, '&', '%', or digits.
A line can be split by substituting a <newline> into it. The
application shall ensure it escapes the <newline> in the
replacement by preceding it by <backslash>. Such substitution
cannot be done as part of a g or v command list. The current
line number shall be set to the address of the last line on which
a substitution is performed. If no substitution is performed, the
current line number shall be unchanged. If a line is split, a
substitution shall be considered to have been performed on each
of the new lines for the purpose of determining the new current
line number. A substitution shall be considered to have been
performed even if the replacement string is identical to the
string that it replaces.
The application shall ensure that the value of flags is zero or
more of:
count Substitute for the countth occurrence only of the RE
found on each addressed line.
g Globally substitute for all non-overlapping instances of
the RE rather than just the first one. If both g and
count are specified, the results are unspecified.
l Write to standard output the final line in which a
substitution was made. The line shall be written in the
format specified for the l command.
n Write to standard output the final line in which a
substitution was made. The line shall be written in the
format specified for the n command.
p Write to standard output the final line in which a
substitution was made. The line shall be written in the
format specified for the p command.
Copy Command
Synopsis:
(.,.)taddress
The t command shall be equivalent to the m command, except that a
copy of the addressed lines shall be placed after address address
(which can be 0); the current line number shall be set to the
address of the last line added.
Undo Command
Synopsis:
u
The u command shall nullify the effect of the most recent command
that modified anything in the buffer, namely the most recent a,
c, d, g, i, j, m, r, s, t, u, v, G, or V command. All changes
made to the buffer by a g, G, v, or V global command shall be
undone as a single change; if no changes were made by the global
command (such as with g/RE/p), the u command shall have no
effect. The current line number shall be set to the value it had
immediately before the command being undone started.
Global Non-Matched Command
Synopsis:
(1,$)v/RE/command list
This command shall be equivalent to the global command g except
that the lines that are marked during the first step shall be
those for which the line excluding the terminating <newline> does
not match the RE.
Interactive Global Not-Matched Command
Synopsis:
(1,$)V/RE/
This command shall be equivalent to the interactive global
command G except that the lines that are marked during the first
step shall be those for which the line excluding the terminating
<newline> does not match the RE.
Write Command
Synopsis:
(1,$)w [file]
The w command shall write the addressed lines into the file named
by the pathname file. The command shall create the file, if it
does not exist, or shall replace the contents of the existing
file. The currently remembered pathname shall not be changed
unless there is no remembered pathname. If no pathname is given,
the currently remembered pathname, if any, shall be used (see the
e and f commands); the current line number shall be unchanged. If
the command is successful, the number of bytes written shall be
written to standard output, unless the -s option was specified,
in the following format:
"%d\n", <number of bytes written>
If file begins with '!', the rest of the line shall be taken to
be a shell command line whose standard input shall be the
addressed lines. Such a shell command line shall not be
remembered as the current pathname. This usage of the write
command with '!' shall not be considered as a ``last w command
that wrote the entire buffer'', as described previously; thus,
this alone shall not prevent the warning to the user if an
attempt is made to destroy the editor buffer via the e or q
commands.
Line Number Command
Synopsis:
($)=
The line number of the addressed line shall be written to
standard output in the following format:
"%d\n", <line number>
The current line number shall be unchanged by this command.
Shell Escape Command
Synopsis:
!command
The remainder of the line after the '!' shall be sent to the
command interpreter to be interpreted as a shell command line.
Within the text of that shell command line, the unescaped
character '%' shall be replaced with the remembered pathname; if
a '!' appears as the first character of the command, it shall be
replaced with the text of the previous shell command executed via
'!'. Thus, "!!" shall repeat the previous !command. If any
replacements of '%' or '!' are performed, the modified line
shall be written to the standard output before command is
executed. The ! command shall write:
"!\n"
to standard output upon completion, unless the -s option is
specified. The current line number shall be unchanged.
Null Command
Synopsis:
(.+1)
An address alone on a line shall cause the addressed line to be
written. A <newline> alone shall be equivalent to "+1p". The
current line number shall be set to the address of the written
line.
