0. NAME	ag		Anthony's Grep1. SYNOPSIS	ag <pattern> [file...]2. DESCRIPTIONThe AG utility shall search input files, selecting lines matching apattern.  An input line shall be selected if the pattern, treated as asubset of Extended Regular Expressions as described by POSIX.2Standard section 2.8.4, matches any part of the line; a null patternshall match every line.  Each selected input line shall be written tothe standard output.Regular expression matching shall be based on text lines, which areseparated by a <newline> character.  A regular expression cannotcontain a <newline> and there is no way for a pattern to match a<newline> found in the input.3. OPTIONSNone.4. OPERANDSpattern         Specify one pattern to be used during the search for		input.  See Extended Regular Exprssions below on what		constitutes a valid pattern.file            A pathname of a file to be searched for the pattern.		If no file operands are specified or the file operand		is dash (-), the standard input shall be used.5. EXTERNINAL INFLUENCES5.1. STANDARD INPUTThe standard input shall be used only if no file operands arespecifed.  See Input Files.5.2. INPUT FILESThe input files shall be text files.5.3. ENVIRONMENT VARIABLESNo environment variables are used.5.4. ASYNCHRONOUS EVENTSDefault.6. EXTERNAL EFFECTS6.1. STANDARD OUTPUTFor each selected input line from a file, a single output line shallbe written:	"%s:%s\n", file, lineStandard input will have the filename dash (-).6.2. STANDARD ERRORStandard error is used for diagnostic messages only.6.3. OUTPUT FILESNone.7. EXTENDED DESCRIPTION7.1. EXTENDED REGULAR EXPRESSIONS7.1.1. MATCHING A SINGLE CHARACTERAn ERE ordinary character, a special character preceded by abackslash, or a period shall match a single character.  A bracketexpression shall match a single character.  An ERE matching a singlecharacter enclosed in parentheses shall match the same as the EREwithout parentheses would have matched.7.1.1.1. ERE ORDINARY CHARACTERSAn oridinary character is an ERE that matches itself.  An ordinarycharacter is any character in the supported character set, except forthe ERE special characters listed in 7.1.1.2.  The interpretation ofan ordinary character preceded by a backslash (\) is the ordinarycharacter.7.1.1.2. ERE SPECIAL CHARACTERSAn ERE special character has special properties in certain contexts.Outside of those contexts, or when preceded by a backslash, such acharacter shall be an ERE that matches the special character itself.The extended regular expression special characters and the contexts inwhich they have their special meaning are:	. [ \ (         The period, left-bracket, backslash, and left-			parenthesis are special except when used in a			bracket expression.  Outside a bracket			expression, a left-parenthesis immediately			followed by a right-parenthesis will be			treated as a null expression.	)               The right-parenthesis is special when matched			with a preceding left-parenthesis, both			outside of a bracket expression.	* ?             The asterisk and question-mark are special			except when used in a bracket expression.			Results are undefined if this character			appears first in an ERE, or immediately			following a vertial-line, circumflex, or			left-parenthesis.	|               The vertical-line is special except when used			in a bracket expression.  A vertical-line			appearing first or last in an ERE or			immediately following a vertical-line or			left-parenthesis, or preceding a			right-parenthesis, produces a null expression.	^               The circumflex shall be special when used as			an anchor or, as the first character of a			bracket expression.	$               The dollar-sign shall be special when used as			an anchor.7.1.1.3 PERIODS IN EREA period (.), when used outside of a bracket expression, is an EREthat shall match any character in the supported character set exceptNUL.7.1.2. ERE BRACKET EXPRESSIONA bracket expression (an expression enclosed in square brackets, []),is an ERE that matches a single character contained in the nonemptyset of characters represented by the bracket expression.The following rules and definitions apply to bracket expressions:   1)   A bracket expression is either a matching list expression	or a nonmatching list expression.  It consists of one or more	characters and/or range expressions.  The right-bracket (])	shall lose its special meaning and represent itself in a	bracket expression if it occurs first in the list [after an	initial circumflex (^), if any].  Otherwise, it shall	terminate the bracket expression.  The special characters	period (.), asterisk (*), left-bracket ([), and backslash (\)	shall lose their special meaning within a bracket expression.   2)   A matching list expression specifies a list that shall match	any one of the expressions represented in the list.  The first	character of the list shall not be the circumflex.  For	example,  [abc]  is an ERE that matches any of a, b, or c.   3)   A nonmatching list expression begins with a circumflex (^),	and specifies a list that shall match any character except for	the expressions represented in the list after the leading	circumflex.  For example,  [^abc]  is an ERE that matches any	character except a, b, or c.  The circumflex shall have this	special meaning only when it occurs first in the list,	immediately following the left-bracket.   4)   A range expression represents the set of characters that	fall between two elements in the current collation sequence,	inclusive.  It shall be expressed as the starting point and	the ending point separated by a hyphen (-).	In the following, all examples assume the collation sequence	specified for the POSIX Locale (a.k.a ASCII Character Set),	unless another collation sequence is sepecifically defined	by the hardware.	The starting range point and the ending range point shall be a	collating element (character).  The ending range point shall	collate higher than the starting range point; otherwise the	expression shall be treated as invalid.	The interpretation of a range expression where the ending	range point is the starting range point of a subsequent range	expression is undefined.	The hyphen character shall be treated as itself if it occurs	first (after an initial ^, if any) or last in the list, or as	an ending range point in a range expression.  As examples, the	expressions  [-ac]  and  [ac-] are equivalent and match any of	the characters a, c, or -; the expressions  [^-ac]  and [^ac-]	are equivalent and match ant character except a, c, -; the	expression  [%--]  matches any of the characters between % and	- inclusive;  the expression  [--@]  matches any of the	characters between - and @ inclusive; and the expression	[a--@] is invalid, because the letter a follows the symbol -	in the POSIX Locale.7.1.3. ERE MATCHING MULTIPLE CHARACTERSThe following rules shall be used to construct EREs matching multiplecharacters from EREs matching a single character:   1)   A concatenation of EREs shall match the concatenation of the	character sequences matched by each component of the ERE.  A	concatenation of EREs enclosed in parentheses shall match	whatever the concatenation without parentheses matches.  For	example, both the ERE cd and the ERE (cd) are matched by the	third and forth character of the string abcdefabcdef.   2)   When an ERE matching a single character, or a concatention of	EREs enclosed in parentheses is followed by the special	character asterisk (*), together with that asterisk it shall	match what zero or more consecutive occurences of the ERE	would match.  For example, the ERE b*c matches the first	character in the string cabbbcde, and the ERE b*cd matches the	third through seventh characters in the string	cabbbcdebbbbbbcdbc.  And, [ab]* and [ab][ab] are equivalent	when matching the string ab.    3)  When an ERE matching a single character or an ERE enclosed in	parentheses is followed by the special character question-mark	(?), together with that question mark it shall match what zero	or one consecutive occurences of the ERE would match.  For	example, the ERE b?c matches the second character in the	string acabbbcde.The behaviour of multiple adjacent duplication symbols (*, ?) producesundefined results.7.1.4. ERE ALTERATIONTwo EREs separated by the special character vertical-line (|) shallmatch a string that is matched by either.  For example, the EREa((bc)|d) matches the string abc and the string ad.  Singlecharacters, or expressions matching single characters, separated bythe vertical-line and enclosed in parentheses, shall be treated as anERE matching a single character.7.1.5. ERE PRECEDENCEThe order of precedence shall be as shown in the table below, from high to low:	escaped characters			\<special character>	bracket expression			[ ]	grouping				( )	single-character-ERE duplication	* ?	concatenation	anchoring				^ $	alteration				|For example, the ERE abba|cde matches either the string abba or thestring cde (because concatenation has a higher order of precedencethan alteration).7.1.6. ERE EXPRESSION ANCHORINGAn ERE can be limited to matching strings that begin or end a line;this is called anchoring.  The circumflex and dollar-sign specialcharacters shall be considered ERE anchors in the following contexts:   1)   A circumflex (^) outside a bracket expression shall anchor	the (sub)expression it begins to the beginning of a string;	such a (sub)expression can match only a sequence starting at	the first character of a string.  For example, the EREs ^ab	and (^ab) match ab in the string abcdef, but fail to match in	the string cdefab, and the ERE a^b is valid, but can never	match because the character a prevents the expression ^b from	matching the first character of a string.   2)   A dollar-sign ($) outside a bracket expression shall anchor	the (sub)expression it ends to the end of a string; such a	(sub)expression can match only a sequence ending at the last	character of a string.  For example, the EREs ef$ and (ef$)	match ef in the string abcdef, but fail to match in the string	cdefab, and the ERE e$f is valid, but can never match because	the character f prevents the expression e$ from matching the	last character of a string.8. EXIT STATUSThe following exit codes will be returned: 	0	Successful match.	1	No match.	2	Usage error.	3	General error.9. INSTALLATIONAG can be built on any system providing at least K&R C.  It has been tested on 	o  SunOS with GCC	o  ATARI Mega ST with Sozobon C	o  PC clone with Turbo C and WatCom C	o  Interactive UNIX System V/386 release 3.2For most machines, the compile command line should be	cc -O -o ag ag.cPC class machines may require that medium or large memory model be usedand that ARRAY be set to 256.  For Watcom C the command line would be	wcl -ml -DARRAY=256 ag.cThe value ARRAY represents the size of the compiled pattern array andthe size of the array used to record matched states.  The defaultvalue choosen should handle most patterns.  ARRAY can be overridden onthe command line with -DARRAY=nn, where 255 < nn < INT_MAX.10. REFERENCES[Aho86]	Aho, Sethi, and Ullman, "Compilers - Principles, Techniques,	and Tools", Addison-Wesley, 86, ISBN 0-201-10088-6, chapter 3[K&P81] Kernighan and Plauger, "Software Tools in Pascal".	Addison-Wesley, 81, ISBN 0-201-10342-7, chapter 5[Mil87]	Webb Miller, "A Software Tools Sampler", 	Prentice Hall, 87, ISBN 0-13-822305-X, chaper 4[POSIX]	POSIX.2 Standard, 2.8.4 Extended Regular Expressions, 4.28 Grep11. FILESag.c		Obfuscated sourceag.doc		Manual for AGagag.c		Unobfuscated sourcetest.mk		Makefile test driver for AG.12. BUGSThe expression (a*)* compiles but loops forever.There is no check for trailing backslash (\) in the pattern.There is no check for unbalanced brackets.  Omitting a closing bracketwill generate a "Patern too long" error, which is not the real error.13. NOTICESPublic Domain 1992, 1993 by Anthony Howe.  No warranty.