SAM(1)

NAME
sam - screen editor with structural regular expressions

SYNOPSIS
sam [-d] [-S] [-t terminal] file ...
sam -r machine [-s file] [-t terminal] file ...
sam.save
B [-r machine] 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 file to which editing commands apply – whereupon its menu entry is printed. The options are

-d  Do not download the terminal part of. Editing will be done with the command language only, as in ed(1).

-S  Do not attempt to lock the socket used by B. This instance of sam will not be controllable by other commands.

-r machine
    Run the host part remotely on the specified machine, the terminal part locally; or (in the case of the B command) commands to be sent to an instance of sam associated with machine.

-s file
    Start the host part from the indicated file on the remote host.

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

  Text Files
sam can only edit text files, encoded using the encoding specified in the LC_ALL, LC_CTYPE, or LANG environment variables ( see locale(7)). sam supports any encoding supported by the underlying operating system.

Editing files that do not contain valid text in the current encoding (including binary files) will result in a warning and such files generally neither load nor display correctly. The standard iconv(1) utility can be used to convert among various text encodings, and may be useful in converting files to the current encoding for editing.

  Regular expressions
Regular expressions are more-or-less as they are in regex(7), 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 this and the positive form above 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 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 search 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?. ( 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”
    ( A regular expression in double quotes.) 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 evaulated starting at the end of a1.

a1-a2
    The address a2 evaluated looking the reverse direction starting at the beginning of a1.

a1,a2
    The substring from the beinning 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 subtituted. If both a1 and a2 are present and distinguishable, + may be elided. a2 may be a regular expression; if it is delimited by ?"" characters, 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///
    find the second following occurence 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 with 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 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/
    Insert the text into the file after the range. Set dot.

    May also be written as

         a
         lines
         of
         text
         .

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

d   Delete the text in 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 g, as in s/x/y/g, all matches in the range are substituted.

m a1
    Move the range to after a1. Set dot.

t a1
    Copy the range to after a1. Set dot.

  Display commands

P   Print the current file name.

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 name
    Set the current file to the first window on file name, if sam has such a file in its menu. If no such file is present, name is compared against the basename(3) of each menu file, and the first match is made current. Finally, if no such file is present, the first menu file that contains name as a substring is selected. The name may be expressed <shell-command in which case the file names are taken as words (in the shell sense) generated by the shell command and no fuzzy matching is performed.

* B file-list
    Same as b, except that filenames 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 filename.

* 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 delete 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 argument is absent from any of these, the current file name is used. e always sets the file name, r and w will 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 /dev/null, and otherwise unassigned output ( stdout for! and >, stderr for all) is placed in ${HOME}/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 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 commands move further back in time. The only commands for which u is ineffective are cd, u, q, w, and D.

empty
    “The empty string as a command.” 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 the line boundaries and printed. If dot is thereby unchanged, i is set to .+1 and printed.

  Grouping and multiple changes
Commands may be grouped by enclosing them in curly braces. Commands within the braces must appear on separate lines (no backslashes are required between commands) “ as those familiar with other editors might expect ”. Semantically, the opening brance 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 the 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 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.

zerox
    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.

Button 1 changes the 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 (or button 3 combined with the shift key) 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 occurence 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 system-wide text selection. The exchange of a large amount of selected text is truncated to the size of the editor'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.)

The cut and paste operations can also be accessed combinations of mouse buttons, without using the menu. After making a selection with button 1, pressing button 2 with button 1 still pressed will perform a cut operation. Pressing button 3 with button 1 still pressed will perform a paste operation. Performing both of these operations (pressing buttons 2 and then 3 with button 1 still pressed) is the equivalent of the snarf operation. These button combinations are referred to as “chords.”

A scroll wheel, if present, can be used to scroll a file up and down.

Various editing functions are also available via the keyboard. The notation C-x below means “hold the Control key while pressing x” where x is another key.

Key Sequence | Action
C-K | Jump to/from the command window
C-E/X/D/S | Collapse and move selection up/down/right/left
C-W/U | Delete previous word/to beginning of line
C-Backspace | Delete previous word
C-Y | Cut selection
C-C | Snarf selection
C-V | Paste selection
C-Q | Exchange selection
C-Tab | Insert a tab (even when tab expansion is enabled)
Escape | Highlight recently typed text

Note that the key bindings, mouse chords, and scroll wheel configuration can be modified at runtime ( see samrc(5) and Runtime configuration below) and thus may vary depending upon your configuration.

  Runtime configuration
The terminal can be configured at runtime using environment variables ( see below) or by writing a samrc file in your home directory ( see samrc(5)). The terminal's keybindings, mouse chords, tab handling, colors, and fonts may be set at runtime using these methods.

  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 an external file. The answer y causes writing; anything else skips the file. Note that is a shell script, passed directly to sh(1). A modicum of caution should therefore be taken before blindly executing it, especially if one of the files being edited was itself a shell script.

If a machine crash prevents the creation of a file, all changes are lost. If an editing session is difficult to replicate, writing changed files often is recommended.

  Remote execution
sam allows the host and terminal parts of the editor to run on diffrent machines, in a process called “downloading.” This process can be suppressed with the -d option, which then runs only the host part in the manner of ed(1).

Running the host part on another machine is accomplished using the -r option, which is used to specify a remote machine name suitable for passing to the remote shell command specified in the RSH environment variable.

The only component of sam that needs to be on the remote machine is sam, or whatever command specified as the argument to the -s option. Users may also like to have the B command present on the remote system; invoking this command on the remote system will ( if sam was invoked with its default remote host command, i.e. sam) open files in the local terminal. This allows users to run the terminal part of sam locally while controlling it via a remote shell connection.

  Controlling running instances of
B is a shell command that causes a downloaded instance of sam to load the named files. The -r option causes the instance of sam connected to machine to load the named files; the default is the most-recently started local instance.

B may also be called on a remote machine, causing the downloaded instance of sam connected to that machine to load the named files.

ENVIRONMENT
The following environment variables affect the operation of sam:

LC_CTYPE

LC_ALL

LANG
    These variables are consulted to determine the encoding used for text files. Note that the encoding must agree between the host and terminal parts of sam or else communication breaks down.

    For example, when using ssh(1) as the remote shell mechanism, adding

            AcceptEnv LC_CTYPE

    to ssh_config(5) will allow the local character encoding specification to be exported to the remote system. If the host and terminal systems do not support identical character encoding, editing will have undefined results.

FOREGROUND
    Sets the foreground color used by sam to draw its terminal. Common English color names can be used ( see rgb(5)), or exact colors can be specified as #rrggbb, where rr, gg, and bb are hexadecimal digits describing the red, green, and blue components of the color, respectively. By default, this is the string “black.” This can also be set using the foreground directive in samrc(5).

BORDER
    As FOREGROUND, but describing the color used to draw borders. This can also be set using the border directive in samrc(5).

BACKGROUND
    A colon-separated sequence of color descriptions as in FOREGROUND, but describing the background color. By default, this is the string “white.” If multiple colors are specified, sam will cycle through this list when opening new files. Note that the command text will use the first color specified.

    This can also be set using the background directive in samrc(5).

FONT
    A string representing a fc-match(1) compatible font pattern. The font described by this pattern will be used to render text in the terminal. By default, this is the string “monospace.” This can also be set using the font directive in samrc(5).

RSH The name of a command to be used to connect to a remote machine when sam is invoked with the -r option. It will be passed arguments of the form:

            -R REMOTE:LOCAL MACHINE COMMAND

    where REMOTE is the name of the remote UNIX domain socket for remote control, LOCAL is the name of the local UNIX domain socket for remote control, MACHINE is the hostname to connect to, and COMMAND is the command ( e.g. sam) to execute on that machine.

    Note that this works out-of-the-box with recent versions of ssh(1). Any additional arguments should be passed to the command on the remote machine. By default, this is the string “ssh.”

SAMRC
    If set, provides the name of the samrc(5) file to read at startup. By default, this is ${HOME}/.samrc.

SAMSOCKETPATH
    Names a directory in which sam remote control sockets should be placed. By default, the contents of HOME are used.

SAMSOCKETNAME
    Gives a full path name for a sam remote control socket; this will be used in preference to any file in the SAMSOCKETPATH directory.

RSAMSOCKETPATH
    Names a directory in which sam remote control sockets should be placed on remote systems.

TABS
    A number between 1 and 12, indicating the width of a tab character. This number is treated as a multiplier of the width of the '0' character. The default is 8.

    If the number specified for TABS is negative, the absolute value of that number is used and automatic tab expansion is enabled. Tab behavior can also be controlled using the tabs and expandtabs directives in samrc(5).

SHELL
    Specifies the full path of the shell to use for executing external commands.

FILES

${HOME}/.samrc
    Provides runtime configuration of key bindings, mouse chords, colors, fonts, and tabs.

${HOME}/sam.save
    Created if sam terminates abnormally. Executing this file will prompt the user to restore the files that were being edited at the time of termination.

${HOME}/sam.err
    Stores output of shell commands executed by.

SEE ALSO
ed(1) samrc(5)

BUGS

The only human language in which colors may be specified is English.

The only human language in which output is generated is English.

There is no support for right-to-left text, ligatures, composed characters, or any other complex text rendering.

There is no support for font fallback: characters that do not exist in the configured font will display as unknown characters.