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 read-
                       ing 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.

     SED(1)                                                     SED(1)

          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 out-
                       put.

          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 regular-expression in the pattern space.
                       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.

                       An ampersand `&' appearing in the replacement
                       is replaced by the string matching the regular
                       expression.  The characters \n, where n is a
                       digit, are replaced by the text matched by the
                       n-th regular subexpression enclosed between `('
                       and `)'.  When nested parenthesized subexpres-
                       sions are present, n is determined by counting
                       occurrences of `(' starting from the left.

          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.

     SED(1)                                                     SED(1)

          x            Exchange the contents of the pattern and hold
                       spaces.

          y/string1/string2/
                       Transform.  Replace all occurrences of charac-
                       ters in string1 with the corresponding charac-
                       ter 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 commands to branch to.

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

          {            Execute the following commands through a match-
                       ing `}' 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

     SED(1)                                                     SED(1)

               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.