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SDB(1)			    General Commands Manual			SDB(1)

NAME
       sdb - SNOBOL4 debugger

SYNOPSIS
       sdb [ options ...  ] program.sno

DESCRIPTION
       sdb  is a debugger for snobol4(1) programs, in the mold (clawning fone)
       of gdb(1), The GNU debugger.  sdb(1) uses readline(3) for command  line
       editing/history when available.

   Commands:
       break LABEL_OR_STATEMENT_NUMBER
	 Set a breakpoint.

       bt
	 Display call stack backtrace.

       commands	BREAKPOINT_NUMBER
	 Add sdb commands to execute (ie; print	& continue) to a breakpoint.

       condition BREAKPOINT_NUMBER EXPR
	 If EXPR is supplied, it is used as a predicate	to make	the breakpoint
	 conditional.

       continue	EMPTY_OR_COUNT
	 Continue from breakpoint.  The	 optional  count  specifies  how  many
	 times to continue past	this breakpoint	(sets "ignore" count).

       delete BREAKPOINT_NUMBER_OR_EMPTY
	 Delete	a single breakpoint, or	all breakpoints.

       disable BREAKPOINT_NUMBER_OR_EMPTY
	 Temporarily disable a breakpoint, or all breakpoints.

       enable BREAKPOINT_NUMBER_OR_EMPTY
	 Reenable a breakpoint,	or all breakpoints.

       finish
	 Resume	 debugging after current function returns.  Will display func-
	 tion return type and value, if	any.

       help
	 Display help.

       ignore BREAKPOINT_NUMBER	COUNT
	 Set breakpoint	ignore count.

       info
	 Display list of breakpoints and their status.

       list EMPTY_OR_STATEMENT_NUMBER
	 Display source	code.

       next EMPTY_OR_COUNT
	 Single	step execution,	skipping over function calls.

       print EXPRESSION
	 Evaluate expression and print result.	Can be used to call functions,
	 or set	variables.

       quit
	 Exit debugger.

       step EMPTY_OR_COUNT
	 Single	step.

       watch VARIABLE
	 Set watchpoint	on a variable (break when value	changes).

       what
	 Display the datatype of variable contents (or expression).

       where
	 An alias for bt.

       A blank line repeats the	previous command.

       Non-ambiguous abbreviations of commands can be used (ie;	"s", "n").

       The  GNU	 Readline  library (when available) will be used for sdb input
       for command editing and history.

       The keyboard interrupt character	(eg; Control C)	will  stop  a  running
       program and return control to the sdb(1)	command	prompt.

       If  your	program	calls the SDB()	function, it will act as a breakpoint.
       You can check whether sdb(1) is loaded with the FUNCTION	predicate, ie;

		      FUNCTION('SDB') SDB()

SEE ALSO
       snobol4(1), gdb(1), readline(3),	snobol4readline(3)

AUTHOR
       Philip L. Budne

       Inspired	by Fred	Weigel's DDT.SNO and SITBOL's SNODDT.

NOTA BENE
       sdb(1) uses a wide variety  of  system  facilities  and	will  interact
       poorly with any programs	that use any number of features, including:

       o      Altering listing settings	with directive/control lines.

       o      Altering &STLIMIT, &ERRLIMIT, or &TRACE.

       o      Calling SETEXIT()

BUGS
       If  you try to put a breakpoint on a label or line with no code or goto
       fields, the breakpoint will never be triggered.

       You cannot put a	breakpoint on the END label  (however  control	always
       returns to sdb when the END label is reached).

       There is	no "run" command; you cannot restart the program without quit-
       ting and	losing breakpoint settings.

       Interrupt character trapping is in it's infancy,	and only occurs	at the
       start of	a each statement executed.

       The  interrupt  character  is  silently ignored when at the sdb command
       prompt.

       sdb does	not read an init file (ie; .sdbinit).

SNOBOL				   Sep 2013				SDB(1)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | AUTHOR | NOTA BENE | BUGS

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