This manual is for GNU ed (version 1.18, 4 February 2022).
Copyright © 1993, 1994, 2006-2022 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
GNU ed is a line-oriented text editor. It is used to create, display, modify and otherwise manipulate text files, both interactively and via shell scripts. A restricted version of ed, red, can only edit files in the current directory and cannot execute shell commands. Ed is the 'standard' text editor in the sense that it is the original editor for Unix, and thus widely available. For most purposes, however, it is superseded by full-screen editors such as GNU Emacs or GNU Moe.
GNU ed is based on the editor algorithm described in Brian W. Kernighan and P. J. Plauger's book "Software Tools in Pascal", Addison-Wesley, 1981.
If invoked with a file argument, then a copy of file is read into the editor's buffer. Changes are made to this copy and not directly to file itself. Upon quitting ed, any changes not explicitly saved with a 'w' command are lost. In interactive mode, a non-existing file is reported but does not alter the exit status.
Editing is done in two distinct modes: command and input. When first invoked, ed is in command mode. In this mode commands are read from the standard input and executed to manipulate the contents of the editor buffer. A typical command might look like:
which replaces all occurences of the string old with new.
When an input command, such as 'a' (append), 'i' (insert) or 'c' (change), is given, ed enters input mode. This is the primary means of adding text to a file. In this mode, no commands are available; instead, the standard input is written directly to the editor buffer. A line consists of the text up to and including a <newline> character. Input mode is terminated by entering a single period ('.') on a line.
All ed commands operate on whole lines or ranges of lines; e.g., the 'd' command deletes lines; the 'm' command moves lines, and so on. It is possible to modify only a portion of a line by means of replacement, as in the example above. However even here, the 's' command is applied to whole lines at a time.
In general, ed commands consist of zero or more line addresses, followed by a single character command and possibly additional parameters; i.e., commands have the structure:
The addresses indicate the line or range of lines to be affected by the command. If fewer addresses are given than the command accepts, then default addresses are supplied.
ed was created, along with the Unix operating system, by Ken Thompson and Dennis Ritchie. It is the refinement of its more complex, programmable predecessor, QED, to which Thompson and Ritchie had already added pattern matching capabilities (see Regular expressions).
For the purposes of this tutorial, a working knowledge of the Unix shell sh and the Unix file system is recommended, since ed is designed to interact closely with them. (See the bash manual for details about bash).
The principal difference between line editors and display editors is that display editors provide instant feedback to user commands, whereas line editors require sometimes lengthy input before any effects are seen. The advantage of instant feedback, of course, is that if a mistake is made, it can be corrected immediately, before more damage is done. Editing in ed requires more strategy and forethought; but if you are up to the task, it can be quite efficient.
Much of the ed command syntax is shared with other Unix utilities.
As with the shell, <RETURN> (the carriage-return key) enters a line of input. So when we speak of "entering" a command or some text in ed, <RETURN> is implied at the end of each line. Prior to typing <RETURN>, corrections to the line may be made by typing either <BACKSPACE> to erase characters backwards, or <CONTROL>-u (i.e., hold the CONTROL key and type u) to erase the whole line.
When ed first opens, it expects to be told what to do but doesn't prompt us like the shell. So let's begin by telling ed to do so with the <P> (prompt) command:
$ ed P *
By default, ed uses asterisk ('*') as command prompt to avoid confusion with the shell command prompt ('$').
We can run Unix shell (sh) commands from inside ed by prefixing them with <!> (exclamation mark, aka "bang"). For example:
*!date Mon Jun 26 10:08:41 PDT 2006 ! *!for s in hello world; do echo $s; done hello world ! *
So far, this is no different from running commands in the Unix shell. But let's say we want to edit the output of a command, or save it to a file. First we must capture the command output to a temporary location called a buffer where ed can access it. This is done with ed's <r> command (mnemonic: read):
*r !cal -m 137 *
Here ed is telling us that it has just read 137 characters into the editor buffer - i.e., the output of the cal command, which prints a simple ASCII calendar. To display the buffer contents we issue the <p> (print) command (not to be confused with the prompt command, which is uppercase!). To indicate the range of lines in the buffer that should be printed, we prefix the command with <,> (comma) which is shorthand for "the whole buffer":
*,p June 2006 Mo Tu We Th Fr Sa Su 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 *
Now let's write the buffer contents to a file named 'junk' with the <w> (write) command:
*w junk 137 *
Need we say? It's good practice to frequently write the buffer contents, since unwritten changes to the buffer will be lost when we exit ed.
The sample sessions below illustrate some basic concepts of line editing with ed. We begin by creating a file, 'sonnet', with some help from Shakespeare. As with the shell, all input to ed must be followed by a <newline> character. Commands beginning with '#' are taken as comments and ignored. Input mode lines that begin with '#' are just more input.
$ ed # The 'a' command is for appending text to the editor buffer. a No more be grieved at that which thou hast done. Roses have thorns, and filvers foutians mud. Clouds and eclipses stain both moon and sun, And loathsome canker lives in sweetest bud. . # Entering a single period on a line returns ed to command mode. # Now write the buffer to the file 'sonnet' and quit: w sonnet 183 # ed reports the number of characters written. q $ ls -l total 2 -rw-rw-r-- 1 alm 183 Nov 10 01:16 sonnet $
In the next example, some typos are corrected in the file 'sonnet'.
$ ed sonnet 183 # Begin by printing the buffer to the terminal with the 'p' command. # The ',' means "all lines". ,p No more be grieved at that which thou hast done. Roses have thorns, and filvers foutians mud. Clouds and eclipses stain both moon and sun, And loathsome canker lives in sweetest bud. # Select line 2 for editing. 2 Roses have thorns, and filvers foutians mud. # Use the substitute command, 's', to replace 'filvers' with 'silver', # and print the result. s/filvers/silver/p Roses have thorns, and silver foutians mud. # And correct the spelling of 'fountains'. s/utia/untai/p Roses have thorns, and silver fountains mud. w sonnet 183 q $
Since ed is line-oriented, we have to tell it which line, or range of lines we want to edit. In the example above, we do this by specifying the line's number, or sequence in the buffer. Alternatively, we could have specified a unique string in the line, e.g., '/filvers/', where the '/'s delimit the string in question. Subsequent commands affect only the selected line, a.k.a. the current line. Portions of that line are then replaced with the substitute command, whose syntax is 's/old/new/'.
Although ed accepts only one command per line, the print command 'p' is an exception, and may be appended to the end of most commands.
In the next example, a title is added to our sonnet.
$ ed sonnet 183 a Sonnet #50 . ,p No more be grieved at that which thou hast done. Roses have thorns, and silver fountains mud. Clouds and eclipses stain both moon and sun, And loathsome canker lives in sweetest bud. Sonnet #50 # The title got appended to the end; we should have used '0a' # to append "before the first line". # Move the title to its proper place. 5m0p Sonnet #50 # The title is now the first line, and the current address has been # set to the address of this line as well. ,p Sonnet #50 No more be grieved at that which thou hast done. Roses have thorns, and silver fountains mud. Clouds and eclipses stain both moon and sun, And loathsome canker lives in sweetest bud. wq sonnet 195 $
When ed opens a file, the current address is initially set to the address of the last line of that file. Similarly, the move command 'm' sets the current address to the address of the last line moved.
Related programs or routines are vi (1), sed (1), regex (3), sh (1). Relevant documents are:
Unix User's Manual Supplementary Documents: 12 -- 13
B. W. Kernighan and P. J. Plauger: "Software Tools in Pascal", Addison-Wesley, 1981.
The format for running ed is:
ed [options] [file] red [options] [file]
file specifies the name of a file to read. If file is prefixed with a bang (!), then it is interpreted as a shell command. In this case, what is read is the standard output of file executed via sh (1). To read a file whose name begins with a bang, prefix the name with a backslash (\). The default filename is set to file only if it is not prefixed with a bang.
ed supports the following options:
Exit status: 0 if no errors occurred; otherwise >0.
An address represents the number of a line in the buffer. ed maintains a current address which is typically supplied to commands as the default address when none is specified. When a file is first read, the current address is set to the address of the last line of the file. In general, the current address is set to the address of the last line affected by a command.
One exception to the rule that addresses represent line numbers is the address '0' (zero). This means "at the beginning of the buffer", and is valid wherever it makes sense.
An address range is two addresses separated either by a comma (',') or a semicolon (';'). In a semicolon-delimited range, the current address ('.') is set to the first address before the second address is calculated. This feature can be used to set the starting line for searches if the second address contains a regular expression. The value of the first address in a range cannot exceed the value of the second.
Addresses can be omitted on either side of the comma or semicolon separator. If only the first address is given in a range, then the second address is set to the given address. If only the second address is given, the resulting address pairs are '1,addr' and '.;addr' respectively. If a n-tuple of addresses is given where n > 2, then the corresponding range is determined by the last two addresses in the n-tuple. If only one address is expected, then the last address is used. It is an error to give any number of addresses to a command that requires zero addresses.
A line address is constructed as follows:
Addresses can be followed by one or more address offsets, optionally separated by whitespace. Offsets are constructed as follows:
It is not an error if an intermediate address value is negative or greater than the address of the last line in the buffer. It is an error if the final address value is negative or greater than the address of the last line in the buffer. It is an error if a search for a regular expression fails to find a matching line.
Regular expressions are patterns used in selecting text. For example, the ed command
prints all lines containing string. Regular expressions are also used by the 's' command for selecting old text to be replaced with new text.
In addition to specifying string literals, regular expressions can represent classes of strings. Strings thus represented are said to be matched by the corresponding regular expression. If it is possible for a regular expression to match several strings in a line, then the left-most match is the one selected. If the regular expression permits a variable number of matching characters, the longest sequence starting at that point is matched.
An empty regular expression is equivalent to the last regular expression processed. Therefore '/re/s//replacement/' replaces re with replacement.
As a GNU extension, a regular expression /re/ may be followed by the suffix 'I' which makes ed match re in a case-insensitive manner. Note that the suffix is evaluated when the regular expression is compiled, thus it is invalid to specify it together with the empty regular expression.
The following symbols are used in constructing regular expressions using POSIX basic regular expression syntax:
[:alnum:] [:cntrl:] [:lower:] [:space:] [:alpha:] [:digit:] [:print:] [:upper:] [:blank:] [:graph:] [:punct:] [:xdigit:]
If '-' appears as the first or last character of char-class, then it matches itself. All other characters in char-class match themselves.
Patterns in char-class of the form:
where col-elm is a collating element are interpreted according
to 'locale (5)'. See 'regex (7)' for an explanation of these
The following extensions to basic regular expression operators are preceded by a backslash '\' to distinguish them from traditional ed syntax. They may be unavailable depending on the particular regex implementation in your system.
All ed commands are single characters, though some require additional parameters. If a command's parameters extend over several lines, then each line except for the last must be terminated with a backslash ('\').
In general, at most one command is allowed per line. However, most commands accept a print suffix, which is any of 'p' (print), 'l' (list), or 'n' (enumerate), to print the last line affected by the command. It is not portable to give more than one print suffix, but ed allows any combination of non-repeated print suffixes and combines their effects. If any suffix letter is given, it must immediately follow the command.
The 'e', 'E', 'f', 'r', and 'w' commands take an optional file parameter, separated from the command letter by one or more whitespace characters.
An interrupt (typically <Control-C>) has the effect of aborting the current command and returning the editor to command mode.
ed recognizes the following commands. The commands are shown together with the default address or address range supplied if none is specified (in parenthesis).
If file is prefixed with a bang (!), then it is interpreted as a shell command whose output is to be read, (see shell escape command '!' below). In this case the default filename is unchanged.
A warning is printed if any changes have been made in the buffer since
the last 'w' command that wrote the entire buffer to a file.
The first command of command-list must appear on the same line as the
'g' command. The other commands of command-list must appear on
separate lines. All lines of a multi-line command-list except the last
line must be terminated with a backslash ('\'). Any commands are
allowed, except for 'g', 'G', 'v', and 'V'. The '.'
terminating the input mode of commands 'a', 'c', and 'i' can
be omitted if it would be the last line of command-list. By default, a
newline alone in command-list is equivalent to a 'p' command. If
ed is invoked with the command-line option '-G', then a
newline in command-list is equivalent to a '.+1p' command.
The format of command-list is the same as that of the 'g'
command. A newline alone acts as an empty command list. A single '&'
repeats the last non-empty command list.
If file is prefixed with a bang (!), then it is interpreted as a
shell command whose output is to be read, (see shell escape command
'!' below). In this case the default filename is unchanged.
If file is prefixed with a bang (!), then it is interpreted as a
shell command and the addressed lines are written to its standard input,
(see shell escape command '!' below). In this case the default
filename is unchanged. Writing the buffer to a shell command does not
prevent the warning to the user if an attempt is made to overwrite or
discard the buffer via the 'e' or 'q' commands.
The substitute command 's' replaces text in the addressed lines matching a regular expression re with replacement. By default, only the first match in each line is replaced. The syntax of the 's' command is:
The 's' command accepts any combination of the following optional suffixes:
It is an error if no substitutions are performed on any of the addressed lines. The current address is set to the address of the last line on which a substitution occurred. If a line is split, a substitution is considered to have occurred on each of the new lines. If no substitution is performed, the current address is unchanged. The last line modified is copied to the cut buffer.
re and replacement may be delimited by any character other than <space>, <newline> and the characters used by the form of the 's' command shown below. If the last delimiter is omitted, then the last line affected is printed as if the print suffix 'p' were specified. The last delimiter can't be omitted if the 's' command is part of a 'g' or 'v' command-list and is not the last command in the list, because the meaning of the following escaped newline would become ambiguous.
An unescaped '&' in replacement is replaced by the currently matched text. The character sequence '\m' where m is a number in the range [1,9], is replaced by the mth backreference expression of the matched text. If the corresponding backreference expression does not match, then the character sequence '\m' is replaced by the empty string. If replacement consists of a single '%', then replacement from the last substitution is used.
A line can be split by including a newline escaped with a backslash ('\') in replacement. Each backslash in replacement removes the special meaning (if any) of the following character.
ed can repeat the last substitution using the following alternative syntax for the 's' command:
This form of the 's' command accepts the suffixes 'g' and 'count' described above, and any combination of the suffixes 'p' and 'r'. The suffix 'g' toggles the global suffix of the last substitution and resets count to 1. The suffix 'p' toggles the print suffixes of the last substitution. The suffix 'r' causes the re of the last search to be used instead of the re of the last substitution (if the search happened after the substitution).
If the terminal hangs up, ed attempts to write the buffer to the file ed.hup or, if this fails, to $HOME/ed.hup.
ed processes file arguments for backslash escapes, i.e., in a filename, any character preceded by a backslash ('\') is interpreted literally. For example, 'ed 'hello\tworld'' will edit the file 'hellotworld'.
If a text (non-binary) file is not terminated by a newline character, then ed appends one on reading/writing it. In the case of a binary file, ed does not append a newline on reading/writing. A binary file is one containing at least one ASCII NUL character. If the last line has been modified, reading an empty file, for example /dev/null, prior to writing prevents appending a newline to a binary file.
In order to keep track of the text lines in the buffer, ed uses a doubly linked list of structures containing the position and size of each line. This results in a per line overhead of 2 'pointer's, 1 'long int', and 1 'int'. The maximum line length is INT_MAX - 1 bytes. The maximum number of lines is INT_MAX - 2 lines.
When an error occurs, if ed's input is from a regular file or here document, then it exits, otherwise it prints a '?' and returns to command mode. An explanation of the last error can be printed with the 'h' (help) command.
If the 'u' (undo) command occurs in a global command list, then the command list is executed only once.
Attempting to quit ed or edit another file before writing a modified buffer results in an error. If the command is entered a second time, it succeeds, but any changes to the buffer are lost.
There are probably bugs in ed. There are certainly errors and omissions in this manual. If you report them, they will get fixed. If you don't, no one will ever know about them and they will remain unfixed for all eternity, if not longer.
If you find a bug in ed, please send electronic mail to firstname.lastname@example.org. Include the version number, which you can find by running 'ed --version'.
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Copyright (C) year your name. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''.
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If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
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