/*
 * Concatenate files.
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>

/* All comments below this one not in the original file. */
char	stdbuf[BUFSIZ]; /* BUFSIZ is typically 512, according to man page. */

/* Old style function declaration. Return type defaults to int. Param types
 * default to int. You can specify param types (when not int) after the 
 * parentheses like below.
 */
main(argc, argv)
char **argv;
{
	int fflg = 0;         /* Flag set to 1 if reading from stdin */
	register FILE *fi;    /* File handle */
	register c;           /* Current char */
	int dev, ino = -1;    /* Keep track of file inodes */
	struct stat statb;    /* File status struct */

    /* Handle -u flag */
	setbuf(stdout, stdbuf);
	for( ; argc>1 && argv[1][0]=='-'; argc--,argv++) {
		switch(argv[1][1]) {
		case 0:
			break;
		case 'u':  /* -u flag means don't buffer */
			setbuf(stdout, (char *)NULL);
			continue;
		}
		break;
	}

	fstat(fileno(stdout), &statb); /* Get file status. */
	statb.st_mode &= S_IFMT;       /* Use mask to get file type. */

    /* If file is not "character special" or "block special"... */
	if (statb.st_mode!=S_IFCHR && statb.st_mode!=S_IFBLK) {
        /* Save file inode data in local vars */
		dev = statb.st_dev;
		ino = statb.st_ino;
	}

	if (argc < 2) {
		argc = 2;
		fflg++;         /* We're reading from stdin */
	}

	while (--argc > 0) {
		if (fflg || (*++argv)[0]=='-' && (*argv)[1]=='\0')
			fi = stdin;
		else {
			if ((fi = fopen(*argv, "r")) == NULL) {
				fprintf(stderr, "cat: can't open %s\n", *argv);
				continue;
			}
		}

		fstat(fileno(fi), &statb);

        /* Check if we're reading from and writing to same file */
		if (statb.st_dev==dev && statb.st_ino==ino) {
			fprintf(stderr, "cat: input %s is output\n",
			   fflg?"-": *argv);
			fclose(fi);
			continue;
		}

		while ((c = getc(fi)) != EOF)
			putchar(c);

		if (fi!=stdin)
			fclose(fi);
	}
	return(0);
}