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ED(P)			   POSIX Programmer's Manual			 ED(P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       ed - edit text

SYNOPSIS
       ed [-p string][-s][file]

DESCRIPTION
       The ed utility is a line-oriented text editor that uses two modes: com‐
       mand 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	 Vari‐
	      ables  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  expres‐
	      sions.

       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 com‐
	      mand 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 col‐
       lected. 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  cur‐
	   rent	 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	delim‐
	   iter.  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 stop‐
	   ping at the first line for which the line excluding the terminating
	   <newline>  matches the BRE. The BRE consisting of a null BRE delim‐
	   ited 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 deci‐
	   mal 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 sepa‐
       rator, 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  suf‐
       fixed 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  com‐
       mand  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  com‐
       mand 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 exam‐
       ple,  '/'  )  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 num‐
       ber 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  cur‐
       rent  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 num‐
       ber 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 path‐
       name 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	 path‐
       name  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 com‐
       mand. 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 delim‐
       iter 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-exe‐
       cution 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 success‐
       fully executed. (Note that the last command successfully executed shall
       be the G command itself if a command fails or the null command is spec‐
       ified.)	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 subse‐
       quent '?' 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	 char‐
       acter  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 Defini‐
       tions 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,  pre‐
       ceding  each line by its line number and a <tab>; the current line num‐
       ber 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	 writ‐
       ten.  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  replace‐
       ment from beginning to end, the following character shall lose its spe‐
       cial 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 applica‐
       tion shall ensure it escapes the <newline> in the replacement  by  pre‐
       ceding 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 substitu‐
       tion is performed, the current line number shall be  unchanged.	 If  a
       line  is	 split,	 a  substitution shall be considered to have been per‐
       formed 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	speci‐
	      fied, 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  cur‐
       rently  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  num‐
       ber 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	 path‐
       name.  This usage of the write command with '!' shall not be considered
       as a "last w command that wrote the entire buffer", as described previ‐
       ously; 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 out‐
       put 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	 writ‐
       ten.  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 com‐
       mand, 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 implemen‐
       tations 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 '!'	 char‐
	  acters 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 com‐
	  mands.

	* 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 cur‐
	  rent line to that address.

	* BSD does not support the P command; moreover, in BSD it  is  synony‐
	  mous 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;	there‐
       fore, 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 appear‐
       ing in the line is written as "\\" so that the output  is  truly	 unam‐
       biguous.	 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 util‐
       ity 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 com‐
       mand 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  substi‐
       tute command to delete that character.

       It is difficult under some modes of some versions of historical operat‐
       ing system terminal drivers to distinguish between an end-of-file  con‐
       dition  and  terminal disconnect. IEEE Std 1003.1-2001 does not require
       implementations to distinguish between the two situations,  which  per‐
       mits  historical	 implementations of the ed utility on historical plat‐
       forms  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 functional‐
       ity, 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 com‐
       mand "3;/foo/;+2p" will display the first line after line 3  that  con‐
       tains  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, con‐
       sisting solely of comma or semicolon separators; for example, ",,,"  or
       ";;;"  were  considered an error. For consistency of address specifica‐
       tion, 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 prac‐
       tice.

       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 .

IEEE/The Open Group		     2003				 ED(P)
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