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 inputmode. 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.
RegularExpressionsined
The ed utility shall support basic regular expressions, as described in the Base Definitions volume of
POSIX.1‐2017, Section9.3, BasicRegularExpressions. 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.
Addressesined
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.
Commandsined
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 helpmode 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, Chapter11, GeneralTerminalInterface, 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 helpmode has been enabled via the H command) to standard output
and shall continue in command mode with the current line number unchanged.
AppendCommandSynopsis:
(.)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.
ChangeCommandSynopsis:
(.,.)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.
DeleteCommandSynopsis:
(.,.)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.
EditCommandSynopsis:
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", <numberofbytesread>
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.
EditWithoutCheckingCommandSynopsis:
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.
FilenameCommandSynopsis:
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.
GlobalCommandSynopsis:
(1,$)g/RE/commandlist
In the g command, the first step shall be to mark every line for which the line excluding the terminating
<newline> matches the given RE. Then, going sequentially from the beginning of the file to the end of the
file, the given commandlist shall be executed for each marked line, with the current line number set to
the address of that line. Any line modified by the commandlist shall be unmarked. When the g command
completes, the current line number shall have the value assigned by the last command in the commandlist.
If there were no matching lines, the current line number shall not be changed. A single command or the
first of a list of commands shall appear on the same line as the global command. All lines of a multi-
line list except the last line shall be ended with a <backslash> preceding the terminating <newline>; the
a, i, and c commands and associated input are permitted. The '.' terminating input mode can be omitted
if it would be the last line of the commandlist. An empty commandlist shall be equivalent to the p
command. The use of the g, G, v, V, and ! commands in the commandlist produces undefined results. Any
character other than <space> or <newline> can be used instead of a <slash> to delimit the RE. Within the
RE, the RE delimiter itself can be used as a literal character if it is preceded by a <backslash>.
InteractiveGlobalCommandSynopsis:
(1,$)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>.
HelpCommandSynopsis:
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-ModeCommandSynopsis:
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.
InsertCommandSynopsis:
(.)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.
JoinCommandSynopsis:
(.,.+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.
MarkCommandSynopsis:
(.)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.
ListCommandSynopsis:
(.,.)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, Table5-1, EscapeSequencesandAssociatedActions ('\\', '\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.
MoveCommandSynopsis:
(.,.)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.
NumberCommandSynopsis:
(.,.)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 !.
PrintCommandSynopsis:
(.,.)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 !.
PromptCommandSynopsis:
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.
QuitCommandSynopsis:
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.
QuitWithoutCheckingCommandSynopsis:
Q
The Q command shall cause ed to exit without checking whether changes have been made in the buffer since
the last w command.
ReadCommandSynopsis:
($)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", <numberofbytesread>
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.
SubstituteCommandSynopsis:
(.,.)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 vcommandlist. 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.
CopyCommandSynopsis:
(.,.)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.
UndoCommandSynopsis:
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.
GlobalNon-MatchedCommandSynopsis:
(1,$)v/RE/commandlist
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.
InteractiveGlobalNot-MatchedCommandSynopsis:
(1,$)V/RE/
This command shall be equivalent to the interactive global command G except that the lines that are
marked during the first step shall be those for which the line excluding the terminating <newline> does
not match the RE.
WriteCommandSynopsis:
(1,$)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", <numberofbyteswritten>
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.
LineNumberCommandSynopsis:
($)=
The line number of the addressed line shall be written to standard output in the following format:
"%d\n", <linenumber>
The current line number shall be unchanged by this command.
ShellEscapeCommandSynopsis:
!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.
NullCommandSynopsis:
(.+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.
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