datemath.c

应用平台 UNIX 一个时间程序的C代码。 datemath - manipulate dates mathematically

/*
 * $Id: //pentools/main/datemath/datemath.c#5 $
 *
 * written by:  Stephen J. Friedl
 *              Software Consultant
 *              Tustin, California USA
 *              [e-mail]
 *
 *	This tool's home page is
 *
 *		http://www.unixwiz.net/tools/datemath.html
 *
 *	This is the main driver for the datemath program.  The very
 *	large bulk of the code is in the lex scanner specifiction
 *	file "lex.l" and in the yacc grammer file "gram.y", so this
 *	file is little more than a wrapper. It will, however, serve
 *	as an anchor for the documentation.
 *
 *	This program performs various operations on mm/dd/yy, mm/yy,
 *	and YYMM dates, and it sends the results to the standard
 *	output.  This function will most often be used in shell
 *	scripts surrounded by `` characters:
 *
 *		END_DATE=`datemath $YYMM + 3`	# add three months
 *
 *	Datemath is fairly smart about converting from one kind
 *	of date to another when it makes sense, and most operations
 *	can apply to any kind of date.  mm/yy and yymm dates are
 *	both converted to yymm internally, and are used synonymously.
 *
 *	The most common usage will be:
 *
 *		datemath date + num
 *		datemath date - num
 *		datemath date - date
 *
 *	The first two add or subtract the specified number of days/months
 *	for mm/dd/yy or mm/yy dates, and output the same kind of date.
 *	The third form outputs the number of days/months between the
 *	two specified dates in integer form.
 *
 *	This program also supports functions that operate on dates, and
 *	they are:
 *
 *		fday(date)		return mm/dd/yy of first day of month
 *		lday(date)		return mm/dd/yy of last  day of month
 *		ndays(date)		return # of days in this month
 *		year(date)		return year (19YY format)
 *		month(date)		return month of this date
 *		day(date)		return day of this date (mm/dd/yy only)
 *		yymm(date)		convert mm/dd/yy to mm/yy
 *
 *	All expressions have a type: mm/dd/yy, yymm, and integer, and they
 *	can be nested arbitrarily and grouped with parenthesis.  For example
 *	we want to run program "foo" with two mm/dd/yy dates, but all we
 *	have is a mm/yy date in $YYMM.  We would do this with:
 *
 *		foo `datemath fday(yymm)` `datemath lday(yymm+2)`
 *
 *	If we needed to see how many days is in this span, we would do:
 *
 *		datemath '( lday(yymm+2) - fday(yymm) ) + 1'
 *
 *	The string can be separate arguments or a single arg, but
 *	the user must take care to quote characters special to the
 *	shell.
 *
 *	Dates themselves can be in any of the following formats:
 *
 *		mm/yy
 *		yymm
 *		mmddyy
 *		mmddyyyy
 *		mm/dd/yy
 *		mm/dd/yyyy
 *
 *	and full range checking is done on them to make sure the
 *	dates given are plausible.
 *
 *	Currently, "syntax error" is the only indication of most failures,
 *	although some semantic errors (such as the wrong date type) will
 *	be identified.  Exit value is 0 if all is OK and nonzero on error.
 *
 * COMMAND LINE
 *
 *	Other than the expression parsed, a few command-line params
 *	are allowed with the traditional "dash" notation.
 *
 *	-L	This runs only the lexer, not the parser: it's used
 *		for testing the flex code by reading and printing
 *		one token at a time. It does no date math.
 *
 *	-V	print the version of this program.
 *
 *	-9 yy	two-digit years from yy..99 are 1900, and all
 *		else is 2000. Default = 40
 *
 *	-2	output two-digit years
 *
 *	-4	output four-digit years (default)
 *
 *	-C	output dates in Y/M/D format
 *
 * BUGS
 *	> limited error checking of plausible dates
 *	> very poor syntax error recovery
 *	> should be a way to output yymm dates as mm/yy
 *	> no way to do collated date *input*
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <malloc.h>
#include "defs.h"

static const char	Version[] =
	"datemath 2.0.10 - 2003-06-20 - [e-mail]";

const char	*ProgName = NULL;

int		year_digits   = 4,
		collate_order = FALSE;

static void usage(const char *argv0) __attribute__((noreturn));

int main(int argc, char **argv)
{
int	c, i, len;
char	*exprbuf;
int	lextest = FALSE;

	ProgName = argv[0];

	setbuf(stdout, (char *)0);

	while ( (c = getopt(argc, argv, "VL9:24C")) != EOF )
	{
		switch (c)
		{
		  default:
			usage(argv[0]);

		  case '4':
			year_digits = 4;
			break;

		  case '2':
			year_digits = 2;
			break;

		  case 'C':
			collate_order = TRUE;
			break;

		  case '9':
			century19_year = atoi(optarg);
			break;

		  case 'L':
			lextest = TRUE;
			break;

		  case 'V':		/* version */
			fprintf(stderr, "%s\n", Version);
			exit(EXIT_SUCCESS);
		}
	}

	/*----------------------------------------------------------------
	 * BUILD EXPRESSION STRING
	 *
	 * Figure out how much space we need for the whole string,
	 * allocate it, then fill the buffer with it.
	 */
	len = 0;

	for (i = optind; i < argc; i++ )
	{
		len += strlen(argv[i]) + 1;
	}

	if ( len == 0 )
	{
		fprintf(stderr, "ERROR: missing datemath expression\n");

		usage(argv[0]);
	}

	len += 2; /* good measure */

	if ( (exprbuf = malloc(len)) == 0 )
		die("ERROR: cannot get %d bytes of memory", len);

	for ( ; optind < argc; )
	{
		strcat(exprbuf, argv[optind++]);
		strcat(exprbuf, " ");
	}

	init_scan(exprbuf);

	if ( lextest )
	{
	int	tok;

		while ( (tok = yylex()) != 0 )
			printf("got token %d [%s]\n", tok, yytext);

		exit(EXIT_SUCCESS);
	}
	else
	{

		exit( yyparse() == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
	}
}

void yyerror(const char *msg)
{
	die("syntax error in command line: %s", msg);
}

static void usage(const char *argv0)
{
const char *const *p;
static const char * const text[] = {
"",
"  -V        Report version information to stderr and exit",
"  -4        Output dates with four-digit years (default)",
"  -2        Output dates with two-digit years",
"  -9 ##     Two-digit years starting with ## are 19xx, else 20xx",
"  -C        Collate mode: output dates in year/month/day format",
"",
"Expression keywords:",
""
"today tomorrow yesterday -- the obvious dates",
"fday(date) - the first day of the month",
"lday(date) - the last day of the month",
"ndays(date) - number of days in the month",

0

};

	fprintf(stderr, "%s\n\n", Version);
	fprintf(stderr, "usage: %s [options] date-expression\n", argv0);

	for (p = text; *p; p++)
	{
		fprintf(stderr, "%s\n", *p);
	}

	exit(EXIT_FAILURE);
}