awk.shar

c programming pearls answer

-Jun 2, 1999:
-	added function stdinit() to run to initialize files[] array,
-	in case stdin, etc., are not constants; some compilers care.
-
-May 10, 1999:
-	replaced the ERROR ... FATAL, etc., macros with functions
-	based on vprintf, to avoid problems caused by overrunning
-	fixed-size errbuf array.  thanks to ralph corderoy for the
-	impetus, and for pointing out a string termination bug in
-	qstring as well.
-
-Apr 21, 1999:
-	fixed bug that caused occasional core dumps with commandline
-	variable with value ending in \.  (thanks to nelson beebe for
-	the test case.)
-
-Apr 16, 1999:
-	with code kindly provided by Bruce Lilly, awk now parses 
-	/=/ and similar constructs more sensibly in more places.
-	Bruce also provided some helpful test cases.
-
-Apr 5, 1999:
-	changed true/false to True/False in run.c to make it
-	easier to compile with C++.  Added some casts on malloc
-	and realloc to be honest about casts; ditto.  changed
-	ltype int to long in struct rrow to reduce some 64-bit
-	complaints; other changes scattered throughout for the
-	same purpose.  thanks to Nelson Beebe for these portability
-	improvements.
-
-	removed some horrible pointer-int casting in b.c and elsewhere
-	by adding ptoi and itonp to localize the casts, which are
-	all benign.  fixed one incipient bug that showed up on sgi
-	in 64-bit mode.
-
-	reset lineno for new source file; include filename in error
-	message.  also fixed line number error in continuation lines.
-	(thanks to Nelson Beebe for both of these.)
-
-Mar 24, 1999:
-	Nelson Beebe notes that irix 5.3 yacc dies with a bogus
-	error; use a newer version or switch to bison, since sgi
-	is unlikely to fix it.
-
-Mar 5, 1999:
-	changed isnumber to is_number to avoid the problem caused by
-	versions of ctype.h that include the name isnumber.
-
-	distribution now includes a script for building on a Mac,
-	thanks to Dan Allen.
-
-Feb 20, 1999:
-	fixed memory leaks in run.c (call) and tran.c (setfval).
-	thanks to Stephen Nutt for finding these and providing the fixes.
-
-Jan 13, 1999:
-	replaced srand argument by (unsigned int) in run.c;
-	avoids problem on Mac and potentially on Unix & Windows.
-	thanks to Dan Allen.
-
-	added a few (int) casts to silence useless compiler warnings.
-	e.g., errorflag= in run.c jump().
-
-	added proctab.c to the bundle outout; one less thing
-	to have to compile out of the box.
-
-	added calls to _popen and _pclose to the win95 stub for
-	pipes (thanks to Steve Adams for this helpful suggestion).
-	seems to work, though properties are not well understood
-	by me, and it appears that under some circumstances the
-	pipe output is truncated.  Be careful.
-
-Oct 19, 1998:
-	fixed a couple of bugs in getrec: could fail to update $0
-	after a getline var; because inputFS wasn't initialized, 
-	could split $0 on every character, a misleading diversion.
-
-	fixed caching bug in makedfa: LRU was actually removing
-	least often used.
-
-	thanks to ross ridge for finding these, and for providing
-	great bug reports.
-
-May 12, 1998:
-	fixed potential bug in readrec: might fail to update record
-	pointer after growing.  thanks to dan levy for spotting this
-	and suggesting the fix.
-
-Mar 12, 1998:
-	added -V to print version number and die.
-
-Feb 11, 1998:
-	subtle silent bug in lex.c: if the program ended with a number
-	longer than 1 digit, part of the input would be pushed back and
-	parsed again because token buffer wasn't terminated right.
-	example:  awk 'length($0) > 10'.  blush.  at least i found it
-	myself.
-
-Aug 31, 1997:
-	s/adelete/awkdelete/: SGI uses this in malloc.h.
-	thanks to nelson beebe for pointing this one out.
-
-Aug 21, 1997:
-	fixed some bugs in sub and gsub when replacement includes \\.
-	this is a dark, horrible corner, but at least now i believe that
-	the behavior is the same as gawk and the intended posix standard.
-	thanks to arnold robbins for advice here.
-
-Aug 9, 1997:
-	somewhat regretfully, replaced the ancient lex-based lexical
-	analyzer with one written in C.  it's longer, generates less code,
-	and more portable; the old one depended too much on mysterious
-	properties of lex that were not preserved in other environments.
-	in theory these recognize the same language.
-
-	now using strtod to test whether a string is a number, instead of
-	the convoluted original function.  should be more portable and
-	reliable if strtod is implemented right.
-
-	removed now-pointless optimization in makefile that tries to avoid
-	recompilation when awkgram.y is changed but symbols are not.
-
-	removed most fixed-size arrays, though a handful remain, some
-	of which are unchecked.  you have been warned.
-
-Aug 4, 1997:
-	with some trepidation, replaced the ancient code that managed
-	fields and $0 in fixed-size arrays with arrays that grow on
-	demand.  there is still some tension between trying to make this
-	run fast and making it clean; not sure it's right yet.
-
-	the ill-conceived -mr and -mf arguments are now useful only
-	for debugging.  previous dynamic string code removed.
-
-	numerous other minor cleanups along the way.
-
-Jul 30, 1997:
-	using code provided by dan levy (to whom profuse thanks), replaced
-	fixed-size arrays and awkward kludges by a fairly uniform mechanism
-	to grow arrays as needed for printf, sub, gsub, etc.
-
-Jul 23, 1997:
-	falling off the end of a function returns "" and 0, not 0.
-	thanks to arnold robbins.
-
-Jun 17, 1997:
-	replaced several fixed-size arrays by dynamically-created ones
-	in run.c; added overflow tests to some previously unchecked cases.
-	getline, toupper, tolower.
-
-	getline code is still broken in that recursive calls may wind
-	up using the same space.  [fixed later]
-
-	increased RECSIZE to 8192 to push problems further over the horizon.
-
-	added \r to \n as input line separator for programs, not data.
-	damn CRLFs.
-
-	modified format() to permit explicit printf("%c", 0) to include
-	a null byte in output.  thanks to ken stailey for the fix.
-
-	added a "-safe" argument that disables file output (print >,
-	print >>), process creation (cmd|getline, print |, system), and
-	access to the environment (ENVIRON).  this is a first approximation
-	to a "safe" version of awk, but don't rely on it too much.  thanks
-	to joan feigenbaum and matt blaze for the inspiration long ago.
-
-Jul 8, 1996:
-	fixed long-standing bug in sub, gsub(/a/, "\\\\&"); thanks to
-	ralph corderoy.
-
-Jun 29, 1996:
-	fixed awful bug in new field splitting; didn't get all the places
-	where input was done.
-
-Jun 28, 1996:
-	changed field-splitting to conform to posix definition: fields are
-	split using the value of FS at the time of input; it used to be
-	the value when the field or NF was first referred to, a much less
-	predictable definition.  thanks to arnold robbins for encouragement
-	to do the right thing.
-
-May 28, 1996:
-	fixed appalling but apparently unimportant bug in parsing octal
-	numbers in reg exprs.
-
-	explicit hex in reg exprs now limited to 2 chars: \xa, \xaa.
-
-May 27, 1996:
-	cleaned up some declarations so gcc -Wall is now almost silent.
-
-	makefile now includes backup copies of ytab.c and lexyy.c in case
-	one makes before looking; it also avoids recreating lexyy.c unless
-	really needed.
-
-	s/aprintf/awkprint, s/asprintf/awksprintf/ to avoid some name clashes
-	with unwisely-written header files.
-
-	thanks to jeffrey friedl for several of these.
-
-May 26, 1996:
-	an attempt to rationalize the (unsigned) char issue.  almost all
-	instances of unsigned char have been removed; the handful of places
-	in b.c where chars are used as table indices have been hand-crafted.
-	added some latin-1 tests to the regression, but i'm not confident;
-	none of my compilers seem to care much.  thanks to nelson beebe for
-	pointing out some others that do care.
-
-May 2, 1996:
-	removed all register declarations.
-
-	enhanced split(), as in gawk, etc:  split(s, a, "") splits s into
-	a[1]...a[length(s)] with each character a single element.
-
-	made the same changes for field-splitting if FS is "".
-
-	added nextfile, as in gawk: causes immediate advance to next
-	input file. (thanks to arnold robbins for inspiration and code).
-
-	small fixes to regexpr code:  can now handle []], [[], and
-	variants;  [] is now a syntax error, rather than matching 
-	everything;  [z-a] is now empty, not z.  far from complete
-	or correct, however.  (thanks to jeffrey friedl for pointing out
-	some awful behaviors.)
-
-Apr 29, 1996:
-	replaced uchar by uschar everywhere; apparently some compilers
-	usurp this name and this causes conflicts.
-
-	fixed call to time in run.c (bltin); arg is time_t *.
-
-	replaced horrible pointer/long punning in b.c by a legitimate
-	union.  should be safer on 64-bit machines and cleaner everywhere.
-	(thanks to nelson beebe for pointing out some of these problems.)
-
-	replaced nested comments by #if 0...#endif in run.c, lib.c.
-
-	removed getsval, setsval, execute macros from run.c and lib.c.
-	machines are 100x faster than they were when these macros were
-	first used.
-
-	revised filenames: awk.g.y => awkgram.y, awk.lx.l => awklex.l,
-	y.tab.[ch] => ytab.[ch], lex.yy.c => lexyy.c, all in the aid of
-	portability to nameless systems.
-
-	"make bundle" now includes yacc and lex output files for recipients
-	who don't have yacc or lex.
-
-Aug 15, 1995:
-	initialized Cells in setsymtab more carefully; some fields
-	were not set.  (thanks to purify, all of whose complaints i
-	think i now understand.)
-
-	fixed at least one error in gsub that looked at -1-th element
-	of an array when substituting for a null match (e.g., $).
-
-	delete arrayname is now legal; it clears the elements but leaves
-	the array, which may not be the right behavior.
-
-	modified makefile: my current make can't cope with the test used
-	to avoid unnecessary yacc invocations.
-
-Jul 17, 1995:
-	added dynamically growing strings to awk.lx.l and b.c
-	to permit regular expressions to be much bigger.
-	the state arrays can still overflow.
-
-Aug 24, 1994:
-	detect duplicate arguments in function definitions (mdm).
-
-May 11, 1994:
-	trivial fix to printf to limit string size in sub().
-
-Apr 22, 1994:
-	fixed yet another subtle self-assignment problem:
-	$1 = $2; $1 = $1 clobbered $1.
-
-	Regression tests now use private echo, to avoid quoting problems.
-
-Feb 2, 1994:
-	changed error() to print line number as %d, not %g.
-
-Jul 23, 1993:
-	cosmetic changes: increased sizes of some arrays,
-	reworded some error messages.
-
-	added CONVFMT as in posix (just replaced OFMT in getsval)
-
-	FILENAME is now "" until the first thing that causes a file
-	to be opened.
-
-Nov 28, 1992:
-	deleted yyunput and yyoutput from proto.h;
-	different versions of lex give these different declarations.
-
-May 31, 1992:
-	added -mr N and -mf N options: more record and fields.
-	these really ought to adjust automatically.
-
-	cleaned up some error messages; "out of space" now means
-	malloc returned NULL in all cases.
-
-	changed rehash so that if it runs out, it just returns;
-	things will continue to run slow, but maybe a bit longer.
-
-Apr 24, 1992:
-	remove redundant close of stdin when using -f -.
-
-	got rid of core dump with -d; awk -d just prints date.
-
-Apr 12, 1992:
-	added explicit check for /dev/std(in,out,err) in redirection.
-	unlike gawk, no /dev/fd/n yet.
-
-	added (file/pipe) builtin.  hard to test satisfactorily.
-	not posix.
-
-Feb 20, 1992:
-	recompile after abortive changes;  should be unchanged.
-
-Dec 2, 1991:
-	die-casting time:  converted to ansi C, installed that.
-
-Nov 30, 1991:
-	fixed storage leak in freefa, failing to recover [N]CCL.
-	thanks to Bill Jones ([e-mail])
-
-Nov 19, 1991:
-	use RAND_MAX instead of literal in builtin().
-
-Nov 12, 1991:
-	cranked up some fixed-size arrays in b.c, and added a test for
-	overflow in penter.  thanks to mark larsen.
-
-Sep 24, 1991:
-	increased buffer in gsub.  a very crude fix to a general problem.
-	and again on Sep 26.
-
-Aug 18, 1991:
-	enforce variable name syntax for commandline variables: has to
-	start with letter or _.
-
-Jul 27, 1991:
-	allow newline after ; in for statements.
-
-Jul 21, 1991:
-	fixed so that in self-assignment like $1=$1, side effects
-	like recomputing $0 take place.  (this is getting subtle.)
-
-Jun 30, 1991:
-	better test for detecting too-long output record.
-
-Jun 2, 1991:
-	better defense against very long printf strings.
-	made break and continue illegal outside of loops.
-
-May 13, 1991:
-	removed extra arg on gettemp, tempfree.  minor error message rewording.
-
-May 6, 1991:
-	fixed silly bug in hex parsing in hexstr().
-	removed an apparently unnecessary test in isnumber().
-	warn about weird printf conversions.
-	fixed unchecked array overwrite in relex().
-
-	changed for (i in array) to access elements in sorted order.