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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
−a Autoindent. In this mode, when a newline character is typed
in the terminal interface, samterm copies leading white space
on the current line to the new line.
−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 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(7) with the addition of \n
to represent newlines. A regular expression may never contain
a literal newline character. 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 .*\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?
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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.
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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"
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Preceding a simple address (default .), refers to the address
evaluated in the unique file whose menu line matches the regular
expression.
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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 ?’s, 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 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/
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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.
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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
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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.
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* B file-list
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Same as b, except that file names not in the menu are entered
there, and all file names in the list are examined.
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* n Print a menu of files. The format is:
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' or blankindicating 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 blankindicating the current file,
a blank,
and the file name.
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* D file-list
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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.
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I/O Commands
* e filename
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Replace the file by the contents of the named external file. Set
dot to the beginning of the file.
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r filename
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Replace the text in the range by the contents of the named external
file. Set dot.
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w filename
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Write the range (default 0,$) to the named external file.
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* f filename
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Set the file name and print the resulting menu entry.
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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
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Replace the range by the standard output of the Plan 9 command.
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> Plan 9-command
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Send the range to the standard input of the Plan 9 command.
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| Plan 9-command
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Send the range to the standard input, and replace it by the standard
output, of the Plan 9 command.
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* ! Plan 9-command
* cd directory
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Change working directory. If no directory is specified, $HOME
is used.
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In any of <, >, | or !, if the Plan 9 command is omitted 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
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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 range and at the end of the range.
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y/regexp/ command
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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 expression. Null substrings potentially
occur before every character in the range.
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* X/regexp/ command
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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.
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* Y/regexp/ command
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Same as X, but for files that do not match the regular expression,
and the expression is required.
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g/regexp/ command
v/regexp/ command
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If the range contains (g) or does not contain (v) a match for
the expression, set dot to the range and run the command.
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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. If n is negative,
u ‘redoes,’
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undoing the undo, going forwards in time again.
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(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 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 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. 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.
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 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. 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(7)).
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.
<rio> Exchange snarf buffers with rio.
/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.)
Simulated buttons
For systems without a three-button mouse, the keyboard modifier
keys can be used to modify the effect of the main mouse button.
On Unix systems, the Control key changes the main button to button
2, and the Alt key changes it to button 3. On Mac systems, the
Option key changes the main button to button 2, and the Command
key changes it to
button 3. Also on Mac systems, the usual keyboard shortcuts Command-C,
-V, and -X invoke copy, paste, and cut, as in other programs.
External communication
Sam listens to the edit plumb port. If plumbing is not 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 display in the last named file (plumbing
provides a more general
mechanism for this ability).
E is a shell-level command that can be used as $EDITOR in a Unix
environment. It runs B on file and then does not exit until file
is changed, which is taken as a signal that file is done being
edited.
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 executed, asks whether to write
each file back to a external file. The answer y causes writing;
anything else skips the file.
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