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NAME
sam, B, E, sam.save, samterm, samsave - screen editor with structural regular expressions
SYNOPSIS
sam [ option ... ] [ files ]
sam -r machine
sam.save
B file[:line] ...
E 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
-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 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 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 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 (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 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.
< 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 command.
| 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
Run the Plan 9 command.
* cd directory
Change working directory. If no directory is specified, $home is used.
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
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 regular expression. 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. 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 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.)
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 causes writing; anything else skips the file.
FILES
$HOME/sam.save
$HOME/sam.err
/bin/samsave
the program called to unpack $HOME/sam.save.
SOURCE
/src/cmd/sam
source for sam itself
/src/cmd/samterm
source for the separate terminal part
/bin/B
/bin/E
SEE ALSO
ed(1), sed(1), grep(1), rio(1), regexp(7).
Rob Pike, ``The text editor sam''.
SAM(1plan9)