/* +--------------------------------------------+ */
/* |@(#) cntr: usage [width:-80]                | */
/* +--------------------------------------------+ */
#include <stdio.h>
#include <strings.h>
#include <sys/types.h>

#define BMAX	2048
#define WIDTH	 80

char	*verid = "%Z% VAU-1 cntr by ycos %I%";

/*  Error message print */
/*    erprint(prog, message), output stderr */
void erprt( char *prog, char *msg )
{
	fprintf(stderr,"\n%s:%s\n", prog, msg );

	exit(1);
}

main( int argc, char *argv[] )
{
	FILE	*ipt;	/* Input file discripter */
	int	 len,	/* length of input line */
		 mgn,	/* right mergin 	*/
		 wid,	/* output width 	*/
		 i;
	char	buf[BMAX];	/* I/O buffer per 1 line*/

	/* Arguments check( none, width or width filename ) */
	switch( argc ) {
	case 1:
		ipt = stdin;
		wid = WIDTH;
		break;
	case 2:
		ipt = stdin;
		wid = atoi( argv[1] );
		break;
	case 3:
		ipt = fopen(argv[2], "r");
		if( ipt == NULL ) erprt(argv[0],"input file error");
		break;
	default:
		erprt(argv[0],"[ width [file name] ]");
		break;
	}

	if( wid < 3 || wid > BMAX ) erprt(argv[0],"range check. width");

	for(;;){
		if( fgets(buf, BMAX, ipt ) == NULL ) break;
		len = strlen(buf);
		if( wid > len ) {
			mgn = (wid - len ) / 2;
			for(i=0;i<mgn;i++){
				fputc(' ',stdout);
			}
		}
		fputs(buf,stdout);
	}
}