SAM(1)

NAME
sam - 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 current file—that to which editing commands apply—whereupon its menu entry is printed. The options are

-d  Do not download the terminal part of sam. Editing 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 file
    Start the host part from the indicated file on the remote host. Only meaningful with the -r option.

-t path
    Start the terminal part from the indicated file. Useful for debugging.

The standard X11 -geom toolkit option can be used to select the desired window geometry.

  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 elements of regular expressions are:

.   Match any character except newline.

\n  Match newline.

\x  For any character except n match the character (here x).

[abc]
    Match any character in the square brackets. \n may be mentioned.

[^abc]
    Match any character not in the square brackets, but never a newline. Both these forms accept a range of ASCII characters indicated by a dash, as in a-z.

^   Match the null string immediately after a newline.

$   Match the null string immediately before a newline.

Any other character except newline matches itself.

In the following, r1 and r2 are regular expressions.

(r1)
    Match what r1 matches.

r1|r2
    Match what r1 or what r2 matches.

r1* Match zero or more adjacent matches of r1.

r1+ Match one or more adjacent matches of r1.

r1? Match zero or one matches of r1.

The operators *, + and ? are highest precedence, then catenation, then | is lowest. The empty regular expression stands for the last complete expression encountered. A regular expression in sam matches the longest leftmost substring formally matched by the expression. Searching in the reverse direction is equivalent to searching backwards with the catenation operations reversed in the expression.

  Addresses
An address identifies a substring in a file. In the following, `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 beginning of the file, of the regular expression (The peculiar properties of a last line without a newline are temporarily undefined.) 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.

/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 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 the effect of the + or - is reversed.

It is an error for a compound address to represent a malformed 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 ASCII character except alphanumerics. Any number of trailing delimiters may be elided, with multiple 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 newline; 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.

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 substituted. 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 the range to after a1 (m), or copy it (t). 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 <shell command in which case the file names are taken as words (in the shell sense) generated by the shell 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 examined.

* 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.

  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.

< shell-command
    Replace the range by the standard output of the shell command.

> shell-command
    Sends the range to the standard input of the shell command.

| shell-command
    Send the range to the standard input, and replace it by the standard output, of the shell command.

* ! shell-command
    Run the shell command.

* cd directory
    Change working directory. If no directory is specified, $HOME is used.

In any of <, >, | or !, if the shell command is omitted the last shell command (of any type) is substituted. If sam is downloaded, ! sets standard input to and otherwise unassigned output (stdout for ! and >, stderr for all) is placed in 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, is assumed. Null string matches potentially occur before every character of the 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 behavior. 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 command. 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 command 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. Successive u's move further back in time. The only commands for which u is ineffective are cd, u, q, w and D.

(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 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 insertions at the same address are catenated into a single insertion 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 bitmap 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 independent 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 border, to which typed text and editing commands apply. The escape key (ESC) selects (sets dot to) text typed since the last mouse button hit.

The button 3 menu controls window operations. The top of the menu provides the following operators, each of which uses one or more cursors to prompt for selection of a window or sweeping of a rectangle.

new Create a new, empty file: Depress button 3 where one corner of the new rectangle should appear (box cursor), and move the mouse while holding down button 3 to the diagonally opposite corner. `Sweeping' a null rectangle gets a large window, disjoint from the command window or the whole sam window, depending on where the null rectangle is.

xerox
    Create a copy of an existing window. After selecting the window to copy with button 1, sweep out the window for the copy.

reshape
    Change the size and location of a window. First click button 3 in the window to be changed (gunsight cursor). Then sweep out a window as for the new menu selection.

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 current, unless it is already current, in which case selections 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 current 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 interpreted as commands for the editor rather than passive text, and text printed by editor commands appears in it. There is 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
Typed characters replace the current selection (dot) in the current window. Backspace deletes the previous character. Escape selects (sets dot to) everything typed since the last mouse hit.

Button 1 changes selection. 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.

look
    Search forward for the next occurrence of the literal text in dot. If dot is the null string, the text in the snarf buffer is used. The snarf buffer is unaffected.

<exch>
    Exchange the snarf buffer with the current selection in another X11 window. The exchange of a large amount of selected text is truncated to the size of Sam's internal snarf buffer (currently 4K) without warning.

/regexp
    Search forward for the next match of the last regular 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.)

  X11 resources
Various attributes of sam can be set by giving values to X11 resources for the class Sam. There are various ways to do this; one is to have a file called Sam in your home directory, with entries in it like:

    Sam*width: 500
    Sam*height: 600
    Sam*font: fixed
    Sam*scrollForwardR: true

In addition to the usual X11 toolkit resources, the scrollForwardR resource says where the right button (button 3) scrolls forward or backward in the file.

  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, This program, when executed, asks whether to write each file back to a external file. The answer causes writing; anything else skips the file. If a machine crash prevents the creation of a file, all changes are lost. If an editing session is difficult to replicate, you should write your changed files often.

B is a shell-level command that causes an instance of sam running on the same terminal to load the named files. The option allows a line number to be specified for the initial position to display in the last named file.

FILES
<system-dependent dirctory>/samsave the program called to unpack $home/sam.save.

SEE ALSO
ed(1), regexp(6)

BUGS

When a sam window is resized, the command window may have the wrong size.