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 substitutions
          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 pattern space (unless there is something left after a
          `D' 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 cumulatively across files, a `$' that addresses the
          last line of input, or a context address,
          /regular-expression/, in the style of regexp(6), with the
          added convention that `\n' 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 sec-
          ond.  (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).

     SED(1)                                                     SED(1)

          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 `s' 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 com-
          mand 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 pat-
                    tern space.

          h         Replace the contents of the hold space by the con-
                    tents 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 num-
                    ber changes.)

     SED(1)                                                     SED(1)

          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 out-
                    put before reading the next input line.

          s/regular-expression/replacement/flags
                    Substitute the replacement string for instances of
                    the regular-expression in the pattern space, as
                    per regsub in regexp(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 substitutions have been made since the most
                    recent reading of an input line or execution of a
                    `t'.  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.

     SED(1)                                                     SED(1)

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

          =         Place the current line number on the standard out-
                    put 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 `UNIX' by `UNIX system'.

          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 `q' command is executed.