NAME
ed - edit text
SYNOPSIS
ed [-p string][-s][file]
DESCRIPTION
The ed utility is a line-oriented text editor that uses two modes:
command mode and input mode. In command mode the input characters shall
be interpreted as commands, and in input mode they shall be interpreted
as text. See the EXTENDED DESCRIPTION section.
OPTIONS
The ed utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
-p string
Use string as the prompt string when in command mode. By
default, there shall be no prompt string.
-s Suppress the writing of byte counts by e, E, r, and w commands
and of the ’!’ prompt after a !command.
OPERANDS
The following operand shall be supported:
file If the file argument is given, ed shall simulate an e command on
the file named by the pathname, file, before accepting commands
from the standard input. If the file operand is ’-’ , the
results are unspecified.
STDIN
The standard input shall be a text file consisting of commands, as
described in the EXTENDED DESCRIPTION section.
INPUT FILES
The input files shall be text files.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of ed:
HOME Determine the pathname of the user’s home directory.
LANG Provide a default value for the internationalization variables
that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables
used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all
the other internationalization variables.
LC_COLLATE
Determine the locale for the behavior of ranges, equivalence
classes, and multi-character collating elements within regular
expressions.
LC_CTYPE
Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input files)
and the behavior of character classes within regular
expressions.
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error
and informative messages written to standard output.
NLSPATH
Determine the location of message catalogs for the processing of
LC_MESSAGES .
ASYNCHRONOUS EVENTS
The ed utility shall take the standard action for all signals (see the
ASYNCHRONOUS EVENTS section in Utility Description Defaults ) with the
following exceptions:
SIGINT The ed utility shall interrupt its current activity, write the
string "?\n" to standard output, and return to command mode (see
the EXTENDED DESCRIPTION section).
SIGHUP If the buffer is not empty and has changed since the last write,
the ed utility shall attempt to write a copy of the buffer in a
file. First, the file named ed.hup in the current directory
shall be used; if that fails, the file named ed.hup in the
directory named by the HOME environment variable shall be used.
In any case, the ed utility shall exit without returning to
command mode.
SIGQUIT
The ed utility shall ignore this event.
STDOUT
Various editing commands and the prompting feature (see -p) write to
standard output, as described in the EXTENDED DESCRIPTION section.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
The output files shall be text files whose formats are dependent on the
editing commands given.
EXTENDED DESCRIPTION
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 IEEE Std 1003.1-2001, Section 9.3, Basic
Regular Expressions. Since regular expressions in ed are always matched
against single lines (excluding the terminating <newline>s), 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 character ( ’-’ ) followed by a
decimal number shall address the current line plus or minus the
number. A plus-sign or hyphen 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 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 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>s 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>s. The
command letter can be preceded by zero or more <blank>s. 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>s.
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 is detected:
* If the buffer is not empty and has changed since the last write, the
ed utility shall attempt to write a copy of the buffer to a file
named ed.hup in the current directory. If this write fails, ed shall
attempt to write a copy of the buffer to a filename ed.hup in the
directory named by the HOME environment variable. If both these
attempts fail, ed shall exit without saving the buffer.
* The ed utility shall not write the file to the currently remembered
pathname or return to command mode, and shall terminate with a non-
zero exit status.
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>s. 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 IEEE Std 1003.1-2001, 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). If the size of a byte on the system is greater than nine
bits, the format used for non-printable characters is implementation-
defined.
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. 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 ’&’ , ’\’ , ’%’ , 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.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion without any file or command errors.
>0 An error occurred.
CONSEQUENCES OF ERRORS
When an error in the input script is encountered, or when an error is
detected that is a consequence of the data (not) present in the file or
due to an external condition such as a read or write error:
* If the standard input is a terminal device file, all input shall be
flushed, and a new command read.
* If the standard input is a regular file, ed shall terminate with a
non-zero exit status.
The following sections are informative.
APPLICATION USAGE
Because of the extremely terse nature of the default error messages,
the prudent script writer begins the ed input commands with an H
command, so that if any errors do occur at least some clue as to the
cause is made available.
In previous versions, an obsolescent - option was described. This is
no longer specified. Applications should use the -s option. Using - as
a file operand now produces unspecified results. This allows
implementations to continue to support the former required behavior.
EXAMPLES
None.
RATIONALE
The initial description of this utility was adapted from the SVID. It
contains some features not found in Version 7 or BSD-derived systems.
Some of the differences between the POSIX and BSD ed utilities include,
but need not be limited to:
* The BSD - option does not suppress the ’!’ prompt after a ! command.
* BSD does not support the special meanings of the ’%’ and ’!’
characters within a ! command.
* BSD does not support the addresses ’;’ and ’,’ .
* BSD allows the command/suffix pairs pp, ll, and so on, which are
unspecified in this volume of IEEE Std 1003.1-2001.
* BSD does not support the ’!’ character part of the e, r, or w
commands.
* A failed g command in BSD sets the line number to the last line
searched if there are no matches.
* BSD does not default the command list to the p command.
* BSD does not support the G, h, H, n, or V commands.
* On BSD, if there is no inserted text, the insert command changes the
current line to the referenced line -1; that is, the line before the
specified line.
* On BSD, the join command with only a single address changes the
current line to that address.
* BSD does not support the P command; moreover, in BSD it is
synonymous with the p command.
* BSD does not support the undo of the commands j, m, r, s, or t.
* The Version 7 ed command W, and the BSD ed commands W, wq, and z are
not present in this volume of IEEE Std 1003.1-2001.
The -s option was added to allow the functionality of the now withdrawn
- option in a manner compatible with the Utility Syntax Guidelines.
In early proposals there was a limit, {ED_FILE_MAX}, that described the
historical limitations of some ed utilities in their handling of large
files; some of these have had problems with files larger than 100000
bytes. It was this limitation that prompted much of the desire to
include a split command in this volume of IEEE Std 1003.1-2001. Since
this limit was removed, this volume of IEEE Std 1003.1-2001 requires
that implementations document the file size limits imposed by ed in the
conformance document. The limit {ED_LINE_MAX} was also removed;
therefore, the global limit {LINE_MAX} is used for input and output
lines.
The manner in which the l command writes non-printable characters was
changed to avoid the historical backspace-overstrike method. On video
display terminals, the overstrike is ambiguous because most terminals
simply replace overstruck characters, making the l format not useful
for its intended purpose of unambiguously understanding the content of
the line. The historical backslash escapes were also ambiguous. (The
string "a\0011" could represent a line containing those six characters
or a line containing the three characters ’a’ , a byte with a binary
value of 1, and a 1.) In the format required here, a backslash
appearing in the line is written as "\\" so that the output is truly
unambiguous. The method of marking the ends of lines was adopted from
the ex editor and is required for any line ending in <space>s; the ’$’
is placed on all lines so that a real ’$’ at the end of a line cannot
be misinterpreted.
Systems with bytes too large to fit into three octal digits must devise
other means of displaying non-printable characters. Consideration was
given to requiring that the number of octal digits be large enough to
hold a byte, but this seemed to be too confusing for applications on
the vast majority of systems where three digits are adequate. It would
be theoretically possible for the application to use the getconf
utility to find out the CHAR_BIT value and deal with such an algorithm;
however, there is really no portable way that an application can use
the octal values of the bytes across various coded character sets, so
the additional specification was not worthwhile.
The description of how a NUL is written was removed. The NUL character
cannot be in text files, and this volume of IEEE Std 1003.1-2001 should
not dictate behavior in the case of undefined, erroneous input.
Unlike some of the other editing utilities, the filenames accepted by
the E, e, R, and r commands are not patterns.
Early proposals stated that the -p option worked only when standard
input was associated with a terminal device. This has been changed to
conform to historical implementations, thereby allowing applications to
interpose themselves between a user and the ed utility.
The form of the substitute command that uses the n suffix was limited
in some historical documentation (where this was described incorrectly
as "backreferencing"). This limit has been omitted because there is no
reason why an editor processing lines of {LINE_MAX} length should have
this restriction. The command s/x/X/2047 should be able to substitute
the 2047th occurrence of ’x’ on a line.
The use of printing commands with printing suffixes (such as pn, lp,
and so on) was made unspecified because BSD-based systems allow this,
whereas System V does not.
Some BSD-based systems exit immediately upon receipt of end-of-file if
all of the lines in the file have been deleted. Since this volume of
IEEE Std 1003.1-2001 refers to the q command in this instance, such
behavior is not allowed.
Some historical implementations returned exit status zero even if
command errors had occurred; this is not allowed by this volume of
IEEE Std 1003.1-2001.
Some historical implementations contained a bug that allowed a single
period to be entered in input mode as <backslash> <period> <newline>.
This is not allowed by ed because there is no description of escaping
any of the characters in input mode; backslashes are entered into the
buffer exactly as typed. The typical method of entering a single period
has been to precede it with another character and then use the
substitute command to delete that character.
It is difficult under some modes of some versions of historical
operating system terminal drivers to distinguish between an end-of-file
condition and terminal disconnect. IEEE Std 1003.1-2001 does not
require implementations to distinguish between the two situations,
which permits historical implementations of the ed utility on
historical platforms to conform. Implementations are encouraged to
distinguish between the two, if possible, and take appropriate action
on terminal disconnect.
Historically, ed accepted a zero address for the a and r commands in
order to insert text at the start of the edit buffer. When the buffer
was empty the command .= returned zero. IEEE Std 1003.1-2001 requires
conformance to historical practice.
For consistency with the a and r commands and better user
functionality, the i and c commands must also accept an address of 0,
in which case 0i is treated as 1i and likewise for the c command.
All of the following are valid addresses:
+++ Three lines after the current line.
/pattern/-
One line before the next occurrence of pattern.
-2 Two lines before the current line.
3 ---- 2
Line one (note the intermediate negative address).
1 2 3 Line six.
Any number of addresses can be provided to commands taking addresses;
for example, "1,2,3,4,5p" prints lines 4 and 5, because two is the
greatest valid number of addresses accepted by the print command. This,
in combination with the semicolon delimiter, permits users to create
commands based on ordered patterns in the file. For example, the
command "3;/foo/;+2p" will display the first line after line 3 that
contains the pattern foo, plus the next two lines. Note that the
address "3;" must still be evaluated before being discarded, because
the search origin for the "/foo/" command depends on this.
Historically, ed disallowed address chains, as discussed above,
consisting solely of comma or semicolon separators; for example, ",,,"
or ";;;" were considered an error. For consistency of address
specification, this restriction is removed. The following table lists
some of the address forms now possible:
Address Addr1 Addr2 Status Comment
7, 7 7 Historical
7,5, 5 5 Historical
7,5,9 5 9 Historical
7,9 7 9 Historical
7,+ 7 8 Historical
, 1 $ Historical
,7 1 7 Extension
,, $ $ Extension
,; $ $ Extension
7; 7 7 Historical
7;5; 5 5 Historical
7;5;9 5 9 Historical
7;5,9 5 9 Historical
7;$;4 $ 4 Historical Valid, but erroneous.
7;9 7 9 Historical
7;+ 7 8 Historical
; . $ Historical
;7 . 7 Extension
;; $ $ Extension
;, $ $ Extension
Historically, values could be added to addresses by including them
after one or more <blank>s; for example, "3 - 5p" wrote the seventh
line of the file, and "/foo/ 5" was the same as "5 /foo/" . However,
only absolute values could be added; for example, "5 /foo/" was an
error. IEEE Std 1003.1-2001 requires conformance to historical
practice.
Historically, ed accepted the ’^’ character as an address, in which
case it was identical to the hyphen character. IEEE Std 1003.1-2001
does not require or prohibit this behavior.
FUTURE DIRECTIONS
None.
SEE ALSO
Utility Description Defaults , ex , sed , sh , vi
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .