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【C】通用排序程序
作者:昕楠 / 发布于2014/11/18/ 490

	/*
	* SORT - reads line of a file and sorts them in order
	* Copyright 1995 Jim Lynch
	*
	* Adapted for ReactOS
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
	*/

	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <malloc.h>

	#define MAXRECORDS 65536 /* maximum number of records that can be
	 * sorted */
	#define MAXLEN 4095 /* maximum record length */

	int rev; /* reverse flag */
	int help; /* help flag */
	int sortcol; /* sort column */
	int err = 0; /* error counter */

	int
	cmpr(const void *a, const void *b)
	{
	 char *A, *B;

	 A = *(char **) a;
	 B = *(char **) b;

	 if (sortcol > 0) {
	 if (strlen(A) > sortcol)
	 A += sortcol;
	 else
	 A = "";
	 if (strlen(B) > sortcol)
	 B += sortcol;
	 else
	 B = "";
	 }
	 if (!rev)
	 return strcmp(A, B);
	 else
	 return strcmp(B, A);
	}

	void
	usage(void)
	{
	 fputs("SORT\\n", stderr);
	 fputs("Sorts input and writes output to a file, console or a device.\\n", stderr);
	 if (err)
	 fputs("Invalid parameter\\n", stderr);
	 fputs(" SORT [options] < [drive:1][path1]file1 > [drive2:][path2]file2\\n", stderr);
	 fputs(" Command | SORT [options] > [drive:][path]file\\n", stderr);
	 fputs(" Options:\\n", stderr);
	 fputs(" /R Reverse order\\n", stderr);
	 fputs(" /+n Start sorting with column n\\n", stderr);
	 fputs(" /? Help\\n", stderr);
	}

	int main(int argc, char **argv)
	{
	 char temp[MAXLEN + 1];
	 char **list;
	 char *cp; /* option character pointer */
	 int nr;
	 int i;

	 sortcol = 0;
	 rev = 0;
	 while (--argc) {
	 if (*(cp = *++argv) == '/') {
	 switch (cp[1]) {
	 case 'R':
	 case 'r':
	 rev = 1;
	 break;
	 case '?':
	 case 'h':
	 case 'H':
	 help = 1;
	 break;
	 case '+':
	 sortcol = atoi(cp + 1);
	 if (sortcol)
	 sortcol--;
	 break;
	 default:
	 err++;
	 }
	 }
	 }
	 if (err || help) {
	 usage();
	 exit(1);
	 }
	 list = (char **) malloc(MAXRECORDS * sizeof(char *));
	 if (list == NULL) {
	 fputs("SORT: Insufficient memory\\n", stderr);
	 exit(3);
	 }
	 for (nr = 0; nr < MAXRECORDS; nr++) {
	 if (fgets(temp, MAXLEN, stdin) == NULL)
	 break;
	 if(strlen(temp))
	 temp[strlen(temp)-1]='\\0';
	 list[nr] = (char *) malloc(strlen(temp) + 1);
	 if (list[nr] == NULL) {
	 fputs("SORT: Insufficient memory\\n", stderr);
	 exit(3);
	 }
	 strcpy(list[nr], temp);
	 }
	 if (nr == MAXRECORDS) {
	 fputs("SORT: number of records exceeds maximum\\n", stderr);
	 exit(4);
	 }
	 qsort((void *) list, nr, sizeof(char *), cmpr);
	 for (i = 0; i < nr; i++) {
	 fputs(list[i], stdout);
	 fputs("\\n",stdout);
	 }
	 return 0;
	}
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