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SED(1)									SED(1)

NAME
       sed - stream editor

SYNOPSIS
       sed [ -n ] [ -g ] [ -e script ] [ -f sfile ] [ file ...	]

DESCRIPTION
       Sed  copies  the	 named	files (standard input default) to the standard
       output, edited according to a script of commands.  The -f option causes
       the  script  to be taken from file sfile; these options accumulate.  If
       there is just one -e option and no -f's, the option -e may be  omitted.
       The  -n	option	suppresses the default output; -g causes all substitu‐
       tions to be global, as if suffixed g.

       A script consists of editing commands, one per line, of	the  following
       form:

	      [address [, address] ] function [argument ...] [;]

       In  normal  operation sed cyclically copies a line of input into a pat‐
       tern space (unless there is something left after a command), applies in
       sequence all commands whose addresses select that pattern space, and at
       the end of the script copies the pattern space to the  standard	output
       (except under -n) and deletes the pattern space.

       An  address  is either a decimal number that counts input lines cumula‐
       tively across files, a that addresses the last line of input, or a con‐
       text address, /regular-expression/, in the style of regexp(6), with the
       added convention that matches a newline embedded in the pattern space.

       A command line with no addresses selects every pattern space.

       A command line with one address selects each pattern space that matches
       the address.

       A  command line with two addresses selects the inclusive range from the
       first pattern space that matches the first  address  through  the  next
       pattern	space  that  matches  the second.  (If the second address is a
       number less than or equal to the line number first selected,  only  one
       line  is	 selected.)  Thereafter the process is repeated, looking again
       for the first address.

       Editing commands can be applied to non-selected pattern spaces  by  use
       of the negation function (below).

       An  argument  denoted  text  consists of one or more lines, all but the
       last of which end with to hide the newline.  Backslashes	 in  text  are
       treated	like  backslashes in the replacement string of an command, and
       may be used to protect initial blanks and tabs  against	the  stripping
       that is done on every script line.

       An  argument denoted rfile or wfile must terminate the command line and
       must be preceded by exactly one blank.  Each wfile  is  created	before
       processing begins.  There can be at most 120 distinct wfile arguments.

       a\
       text	 Append.   Place  text	on  the output before reading the next
		 input line.

       b label	 Branch to the : command  bearing  the	label.	 If  label  is
		 empty, branch to the end of the script.

       c\
       text	 Change.  Delete the pattern space.  With 0 or 1 address or at
		 the end of a 2-address	 range,	 place	text  on  the  output.
		 Start the next cycle.

       d	 Delete the pattern space.  Start the next cycle.

       D	 Delete	 the  initial segment of the pattern space through the
		 first newline.	 Start the next cycle.

       g	 Replace the contents of the pattern space by the contents  of
		 the hold space.

       G	 Append the contents of the hold space to the pattern space.

       h	 Replace the contents of the hold space by the contents of the
		 pattern space.

       H	 Append the contents of the pattern space to the hold space.

       i\
       text	 Insert.  Place text on the standard output.

       n	 Copy the pattern space to the standard output.	  Replace  the
		 pattern space with the next line of input.

       N	 Append	 the  next  line of input to the pattern space with an
		 embedded newline.  (The current line number changes.)

       p	 Print.	 Copy the pattern space to the standard output.

       P	 Copy the initial segment of the  pattern  space  through  the
		 first newline to the standard output.

       q	 Quit.	 Branch	 to the end of the script.  Do not start a new
		 cycle.

       r rfile	 Read the contents of rfile.  Place them on the output	before
		 reading the next input line.

       s/regular-expression/replacement/flags
		 Substitute  the replacement string for instances of the regu‐
		 lar-expression in the pattern space, as per  regsub  in  reg‐
		 exp(2).   Any	character  may be used instead of For a fuller
		 description see regexp(6).  Flags is zero or more of

		 g	Global.	 Substitute for all non-overlapping  instances
			of  the	 regular expression rather than just the first
			one.

		 p	Print the pattern space if a replacement was made.

		 w wfile
			Write.	 Append	 the  pattern  space  to  wfile	 if  a
			replacement was made.

       t label	 Test.	Branch to the command bearing the label if any substi‐
		 tutions have been made since the most recent  reading	of  an
		 input line or execution of a If label is empty, branch to the
		 end of the script.

       w wfile	 Write.	 Append the pattern space to wfile.

       x	 Exchange the contents of the pattern and hold spaces.

       y/string1/string2/
		 Transform.  Replace all occurrences of characters in  string1
		 with  the corresponding character in string2.	The lengths of
		 string1 and string2 must be equal.

       !function Don't.	 Apply the function (or group, if function is only  to
		 lines not selected by the address(es).

       #	 Comment.  Ignore the rest of the line.

       : label	 This  command does nothing; it bears a label for b and t com‐
		 mands to branch to.

       =	 Place the current line number on the  standard	 output	 as  a
		 line.

       {	 Execute  the  following commands through a matching only when
		 the pattern space is selected.

		 An empty command is ignored.

EXAMPLES
       sed 10q file
	      Print the first 10 lines of the file.

       sed '/^$/d'
	      Delete empty lines from standard input.

       sed 's/UNIX/& system/g'
	      Replace every instance of by

       sed 's/ *$//   drop trailing blanks
       /^$/d	      drop empty lines
       s/  */\	      replace blanks by newlines
       /g
       /^$/d' chapter*
	      Print the files chapter1, chapter2, etc. one word to a line.

       nroff -ms manuscript | sed '
       ${
	    /^$/p     if last line of file is empty, print it
       }
       //N	      if current line is empty, append next line
       /^\n$/D'	      if two lines are empty, delete the first
	      Delete all but one of each group of empty lines from a formatted
	      manuscript.

SOURCE
       /sys/src/cmd/sed.c

SEE ALSO
       ed(1), grep(1), awk(1), lex(1), sam(1), regexp(6)
       L.  E.  McMahon,	 `SED  — A Non-interactive Text Editor', Unix Research
       System Programmer's Manual, Volume 2.

BUGS
       If input is from a pipe, buffering may consume characters beyond a line
       on which a command is executed.

									SED(1)
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