/*
 *	CutLog
 *
 *	Keeps the last nn lines of a text file.
 *
 *	Syntax: cutlog <nn> <file>
 *
 *	Note: this program is slow
 *
 *	A public domain program that may be distributed, sold,
 *	etc without restrictions. You can use this source in
 *	your own programs without credits. Use it at your own risk.
 *
 *	FA 16/01/92
 */
 
#include	<stdio.h>
#include	<stdlib.h>
#include	<string.h>
#define TEMPLEN	255
#define SEPAR		'\\'

int main(int argc, char **argv)
{
	int nl,max,start;
	char *ptr;
	char tempnm[FILENAME_MAX], temp[TEMPLEN];
	FILE *fl,*dl;
	
	if(argc!=3)
	{
		printf("usage:    cutlog <nn> <file>\n"
			  "          <nn>   : number of lines to keep\n"
		  	  "          <file> : file name\n\n");
		return 0;
	}
	
	nl=atoi(argv[1]);
	max=0;
	
	/* first run, count the lines */
	fl=fopen(argv[2],"r");
	if(!fl)
	{
		fprintf(stderr, "cutlog: can't open %s\n.",argv[2]);
		return 1;
	}
	while(fgets(temp,TEMPLEN,fl))
		max++;
	fclose(fl);
	
	start=max-nl;
	if(start>0)
	{
		/* find a temp name */
		strcpy(tempnm,argv[2]);
		ptr=strrchr(tempnm,SEPAR);
		if(ptr)
			strcpy(ptr+1,"cutlog.tmp");
		else
			strcpy(tempnm,"cutlog.tmp");

		if(rename(argv[2],tempnm))
		{
			fprintf(stderr,"cutlog: can't rename %s to %s.\n",argv[2],tempnm);
			return 1;
		}
		
		/* second run, copy */
		fl=fopen(tempnm,"r");
		if(!fl)
			fprintf(stderr, "cutlog: can't open %s.\n",tempnm);
		else
		{
			dl=fopen(argv[2],"w");
			if(!dl)
				fprintf(stderr, "cutlog: can't open %s.\n",argv[2]);
			else
			{
				max=0;
				while(fgets(temp,TEMPLEN,fl))
				{
					max++;
					if(max>start)
					{
						if(fputs(temp,dl)<0)
							fprintf(stderr,"can't write %s.\n",argv[2]);
					}
				}
				fclose(dl);
			}
			fclose(fl);
		}
		
		remove(tempnm);
	}
	else
		printf("%s is not too long.\n",argv[2]);
		
	return 0;
}