SAM(1)                                                     SAM(1)

     NAME
          sam, B, sam.save, samterm - screen editor with structural
          regular expressions

     SYNOPSIS
          sam [ option ... ] [ files ]

          sam -r machine

          sam.save

          B [ -nnnn ] file ...

     DESCRIPTION
          Sam is a multi-file editor.  It modifies a local copy of an
          external file.  The copy is here called a file. The files
          are listed in a menu available through mouse button 3 or the
          n command.  Each file has an associated name, usually the
          name of the external file from which it was read, and a
          `modified' bit that indicates whether the editor's file
          agrees with the external file.  The external file is not
          read into the editor's file until it first becomes the cur-
          rent file-that to which editing commands apply-whereupon its
          menu entry is printed.  The options are

          -a         Autoindent.  In this mode, when a newline charac-
                     ter is typed in the terminal interface, samterm
                     copies leading white space on the current line to
                     the new line.
          -i         Indent with spaces.  In this mode, when a tab
                     character is typed in the terminal interface,
                     samterm will insert spaces until the next tab-
                     stop.  Backspace will delete spaces until the
                     previous tabstop or another character is encoun-
                     tered.
          -d         Do not `download' the terminal part of sam. Edit-
                     ing will be done with the command language only,
                     as in ed(1).
          -r machine Run the host part remotely on the specified
                     machine, the terminal part locally.
          -s path    Start the host part from the specified file on
                     the remote host.  Only meaningful with the -r
                     option.
          -t path    Start the terminal part from the specified file.
                     Useful for debugging.

        Regular expressions
          Regular expressions are as in regexp(6) with the addition of
          \n to represent newlines.  A regular expression may never
          contain a literal newline character.  The empty regular

     SAM(1)                                                     SAM(1)

          expression stands for the last complete expression encoun-
          tered.  A regular expression in sam matches the longest
          leftmost substring formally matched by the expression.
          Searching in the reverse direction is equivalent to search-
          ing backwards with the catenation operations reversed in the
          expression.

        Addresses
          An address identifies a substring in a file.  In the follow-
          ing, `character n' means the null string after the n-th
          character in the file, with 1 the first character in the
          file.  `Line n' means the n-th match, starting at the begin-
          ning of the file, of the regular expression `.*\n?'.  All
          files always have a current substring, called dot, that is
          the default address.

        Simple Addresses
          #n   The empty string after character n; #0 is the beginning
               of the file.
          n    Line n; 0 is the beginning of the file.
          /regexp/
          ?regexp?
               The substring that matches the regular expression,
               found by looking toward the end (/) or beginning (?)
               of the file, and if necessary continuing the search
               from the other end to the starting point of the search.
               The matched substring may straddle the starting point.
               When entering a pattern containing a literal question
               mark for a backward search, the question mark should be
               specified as a member of a class.

          0    The string before the first full line.  This is not
               necessarily the null string; see + and - below.

          $    The null string at the end of the file.

          .    Dot.

          '    The mark in the file (see the k command below).

          "regexp"
               Preceding a simple address (default .), refers to the
               address evaluated in the unique file whose menu line
               matches the regular expression.

        Compound Addresses
          In the following, a1 and a2 are addresses.

          a1+a2  The address a2 evaluated starting at the end of a1.
          a1-a2  The address a2 evaluated looking in the reverse
                 direction starting at the beginning of a1.
          a1,a2  The substring from the beginning of a1 to the end of

     SAM(1)                                                     SAM(1)

                 a2. If a1 is missing, 0 is substituted.  If a2 is
                 missing, $ is substituted.
          a1;a2  Like a1,a2, but with a2 evaluated at the end of, and
                 dot set to, a1.

          The operators + and - are high precedence, while , and ; are
          low precedence.

          In both + and - forms, if a2 is a line or character address
          with a missing number, the number defaults to 1.  If a1 is
          missing, `.'  is substituted.  If both a1 and a2 are present
          and distinguishable, + may be elided.  a2 may be a regular
          expression; if it is delimited by `?''s, the effect of the +
          or - is reversed.

          It is an error for a compound address to represent a mal-
          formed substring.  Some useful idioms: a1+- (a1-+) selects
          the line containing the end (beginning) of a1.  0/regexp/
          locates the first match of the expression in the file.  (The
          form 0;// sets dot unnecessarily.)  ./regexp/// finds the
          second following occurrence of the expression, and
          .,/regexp/ extends dot.

        Commands
          In the following, text demarcated by slashes represents text
          delimited by any printable character except alphanumerics.
          Any number of trailing delimiters may be elided, with multi-
          ple elisions then representing null strings, but the first
          delimiter must always be present.  In any delimited text,
          newline may not appear literally; \n may be typed for new-
          line; and \/ quotes the delimiter, here `/'.  Backslash is
          otherwise interpreted literally, except in s commands.

          Most commands may be prefixed by an address to indicate
          their range of operation.  Those that may not are marked
          with a `*' below.  If a command takes an address and none is
          supplied, dot is used.  The sole exception is the w command,
          which defaults to 0,$.  In the description, `range' is used
          to represent whatever address is supplied.  Many commands
          set the value of dot as a side effect.  If so, it is always
          set to the `result' of the change: the empty string for a
          deletion, the new text for an insertion, etc. (but see the s
          and e commands).

        Text commands
          a/text/
          or
          a
          lines of text
          .    Insert the text into the file after the range.  Set
               dot.

     SAM(1)                                                     SAM(1)

          c
          i    Same as a, but c replaces the text, while i inserts
               before the range.

          d    Delete the text in the range.  Set dot.

          s/regexp/text/
               Substitute text for the first match to the regular
               expression in the range.  Set dot to the modified
               range.  In text the character & stands for the string
               that matched the expression. Backslash behaves as usual
               unless followed by a digit: \d stands for the string
               that matched the subexpression begun by the d-th left
               parenthesis.  If s is followed immediately by a number
               n, as in s2/x/y/, the n-th match in the range is sub-
               stituted.  If the command is followed by a g, as in
               s/x/y/g, all matches in the range are substituted.

          m a1
          t a1 Move (m) or copy (t) the range to after a1. Set dot.

        Display commands
          p    Print the text in the range.  Set dot.
          =    Print the line address and character address of the
               range.
          =#   Print just the character address of the range.

        File commands
          * b file-list
               Set the current file to the first file named in the
               list that sam also has in its menu.  The list may be
               expressed <Plan 9 command in which case the file names
               are taken as words (in the shell sense) generated by
               the Plan 9 command.
          * B file-list
               Same as b, except that file names not in the menu are
               entered there, and all file names in the list are exam-
               ined.
          * n  Print a menu of files.  The format is:
               ' or blank indicating the file is modified or clean,
               - or +     indicating the file is unread or has been
                          read (in the terminal, * means more than one
                          window is open),
               . or blank indicating the current file,
               a blank,
               and the file name.
          * D file-list
               Delete the named files from the menu.  If no files are
               named, the current file is deleted.  It is an error to
               D a modified file, but a subsequent D will delete such
               a file.

     SAM(1)                                                     SAM(1)

        I/O Commands
          * e filename
               Replace the file by the contents of the named external
               file.  Set dot to the beginning of the file.
          r filename
               Replace the text in the range by the contents of the
               named external file.  Set dot.
          w filename
               Write the range (default 0,$) to the named external
               file.
          * f filename
               Set the file name and print the resulting menu entry.
          If the file name is absent from any of these, the current
          file name is used.  e always sets the file name; r and w do
          so if the file has no name.
          < Plan 9-command
               Replace the range by the standard output of the Plan 9
               command.
          > Plan 9-command
               Send the range to the standard input of the Plan 9 com-
               mand.
          ^ Plan 9-command
               Send the standard output of the Plan 9 command to the
               command window.
          | Plan 9-command
               Send the range to the standard input, and replace it by
               the standard output, of the Plan 9 command.
          _ Plan 9-command
               Send the range to the standard input, and send the
               standard output of the Plan 9 command to the command
               window.
          * ! Plan 9-command
               Run the Plan 9 command.
          * cd directory
               Change working directory.  If no directory is speci-
               fied, $home is used.

          In any of <, >, ^, _, | or !, if the Plan 9 command is omit-
          ted the last Plan 9 command (of any type) is substituted.
          If sam is downloaded (using the mouse and raster display,
          i.e. not using option -d), ! sets standard input to
          /dev/null, and otherwise unassigned output (stdout for ! and
          >, stderr for all) is placed in /tmp/sam.err and the first
          few lines are printed.

        Loops and Conditionals
          x/regexp/ command
               For each match of the regular expression in the range,
               run the command with dot set to the match.  Set dot to
               the last match.  If the regular expression and its
               slashes are omitted, `/.*\n/' is assumed.  Null string
               matches potentially occur before every character of the

     SAM(1)                                                     SAM(1)

               range and at the end of the range.
          y/regexp/ command
               Like x, but run the command for each substring that
               lies before, between, or after the matches that would
               be generated by x.  There is no default regular expres-
               sion.  Null substrings potentially occur before every
               character in the range.
          * X/regexp/ command
               For each file whose menu entry matches the regular
               expression, make that the current file and run the com-
               mand.  If the expression is omitted, the command is run
               in every file.
          * Y/regexp/ command
               Same as X, but for files that do not match the regular
               expression, and the expression is required.
          g/regexp/ command
          v/regexp/ command
               If the range contains (g) or does not contain (v) a
               match for the expression, set dot to the range and run
               the command.
          These may be nested arbitrarily deeply, but only one
          instance of either X or Y may appear in a single command.
          An empty command in an x or y defaults to p; an empty com-
          mand in X or Y defaults to f.  g and v do not have defaults.

        Miscellany
          k        Set the current file's mark to the range.  Does not
                   set dot.
          * q      Quit.  It is an error to quit with modified files,
                   but a second q will succeed.
          * u n    Undo the last n (default 1) top-level commands that
                   changed the contents or name of the current file,
                   and any other file whose most recent change was
                   simultaneous with the current file's change.  Suc-
                   cessive u's move further back in time.  The only
                   commands for which u is ineffective are cd, u, q, w
                   and D.  If n is negative, u `redoes,' undoing the
                   undo, going forwards in time again.
          (empty)  If the range is explicit, set dot to the range.  If
                   sam is downloaded, the resulting dot is selected on
                   the screen; otherwise it is printed.  If no address
                   is specified (the command is a newline) dot is
                   extended in either direction to line boundaries and
                   printed.  If dot is thereby unchanged, it is set to
                   .+1 and printed.

        Grouping and multiple changes
          Commands may be grouped by enclosing them in braces {}.
          Commands within the braces must appear on separate lines (no
          backslashes are required between commands).  Semantically,
          an opening brace is like a command: it takes an (optional)
          address and sets dot for each sub-command.  Commands within

     SAM(1)                                                     SAM(1)

          the braces are executed sequentially, but changes made by
          one command are not visible to other commands (see the next
          paragraph).  Braces may be nested arbitrarily.

          When a command makes a number of changes to a file, as in
          x/re/c/text/, the addresses of all changes to the file are
          computed in the original file.  If the changes are in
          sequence, they are applied to the file.  Successive inser-
          tions at the same address are catenated into a single inser-
          tion composed of the several insertions in the order
          applied.

        The terminal
          What follows refers to behavior of sam when downloaded, that
          is, when operating as a display editor on a raster display.
          This is the default behavior; invoking sam with the -d (no
          download) option provides access to the command language
          only.

          Each file may have zero or more windows open.  Each window
          is equivalent and is updated simultaneously with changes in
          other windows on the same file.  Each window has an indepen-
          dent value of dot, indicated by a highlighted substring on
          the display.  Dot may be in a region not within the window.
          There is usually a `current window', marked with a dark bor-
          der, to which typed text and editing commands apply.  Text
          may be typed and edited as in rio(1); also the escape key
          (ESC) selects (sets dot to) text typed since the last mouse
          button hit.

          Ctrl+b switches to the command window and moves to the end
          of the text.

          The button 3 menu controls window operations.  The top of
          the menu provides the following operators, each of which
          uses one or more rio-like cursors to prompt for selection of
          a window or sweeping of a rectangle.  `Sweeping' a null
          rectangle gets a large window, disjoint from the command
          window or the whole screen, depending on where the null
          rectangle is.

          new     Create a new, empty file.
          zerox   Create a copy of an existing window.
          resize  As in rio.
          close   Delete the window.  In the last window of a file,
                  close is equivalent to a D for the file.
          write   Equivalent to a w for the file.

          Below these operators is a list of available files, starting
          with ~~sam~~, the command window.  Selecting a file from the
          list makes the most recently used window on that file cur-
          rent, unless it is already current, in which case selections

     SAM(1)                                                     SAM(1)

          cycle through the open windows.  If no windows are open on
          the file, the user is prompted to open one.  Files other
          than ~~sam~~ are marked with one of the characters -+*
          according as zero, one, or more windows are open on the
          file.  A further mark `.'  appears on the file in the cur-
          rent window and a single quote, ', on a file modified since
          last write.

          The command window, created automatically when sam starts,
          is an ordinary window except that text typed to it is inter-
          preted as commands for the editor rather than passive text,
          and text printed by editor commands appears in it.  The
          behavior is like rio, with an `output point' that separates
          commands being typed from previous output.  Commands typed
          in the command window apply to the current open file-the
          file in the most recently current window.

        Manipulating text
          Button 1 changes selection, much like rio. Pointing to a
          non-current window with button 1 makes it current; within
          the current window, button 1 selects text, thus setting dot.
          Double-clicking selects text to the boundaries of words,
          lines, quoted strings or bracketed strings, depending on the
          text at the click.

          Button 2 provides a menu of editing commands:

          cut      Delete dot and save the deleted text in the snarf
                   buffer.
          paste    Replace the text in dot by the contents of the
                   snarf buffer.
          snarf    Save the text in dot in the snarf buffer.
          plumb    Send the text in the selection as a plumb message.
                   If the selection is empty, the white-space-
                   delimited block of text is sent as a plumb message
                   with a click attribute defining where the selection
                   lies (see plumb(6)).
          look     Search forward for the next occurrence of the lit-
                   eral text in dot.  If dot is the null string, the
                   text in the snarf buffer is used.  The snarf buffer
                   is unaffected.
          <rio>    Exchange snarf buffers with rio.
          /regexp  Search forward for the next match of the last regu-
                   lar expression typed in a command.  (Not in command
                   window.)
          send     Send the text in dot, or the snarf buffer if dot is
                   the null string, as if it were typed to the command
                   window.  Saves the sent text in the snarf buffer.
                   (Command window only.)

        External communication
          Sam listens to the edit plumb port.  If plumbing is not

     SAM(1)                                                     SAM(1)

          active, on invocation sam creates a named pipe /srv/sam.user
          which acts as an additional source of commands.  Characters
          written to the named pipe are treated as if they had been
          typed in the command window.

          B is a shell-level command that causes an instance of sam
          running on the same terminal to load the named files. B uses
          either plumbing or the named pipe, whichever service is
          available.  If plumbing is not enabled, the option allows a
          line number to be specified for the initial position to dis-
          play in the last named file (plumbing provides a more gen-
          eral mechanism for this ability).

        Abnormal termination
          If sam terminates other than by a q command (by hangup,
          deleting its window, etc.), modified files are saved in an
          executable file, $home/sam.save.  This program, when exe-
          cuted, asks whether to write each file back to a external
          file.  The answer `y' causes writing; anything else skips
          the file.

     FILES
          $home/sam.save
          $home/sam.err
          /sys/lib/samsave      the program called to unpack
                                $home/sam.save.

     SOURCE
          /sys/src/cmd/sam      source for sam itself
          /sys/src/cmd/samterm  source for the separate terminal part
          /rc/bin/B

     SEE ALSO
          ed(1), sed(1), grep(1), rio(1), regexp(6).

          Rob Pike, ``The text editor sam''.