/*
 * Concatenate files.
 *
 */

char    ibuf[512];
char    obuf[512];

main(argc, argv)
char **argv;
{
        register char *cpi, *cpo;
        register n;
        int ubf;
        int silent;
        int fi;
        int fflg;

        fflg = 0;
        ubf = 0;
        silent = 0;
        cpi = argv[1];
        while (argc > 1 && cpi[0] == '-' && cpi[1] != '\0' && cpi[2] == '\0') {
                switch (cpi[1]) {
                case 'u':
                        argv++;
                        argc--;
                        ubf++;
                        break;
                case 's':
                        argv++;
                        argc--;
                        silent++;
                        break;
                default:
                        argv++;
                        argc--;
                        badflag(cpi);
                }
                cpi = argv[1];
        }
        if (argc<2) {
                argc = 2;
                fflg++;
        }
        cpo = obuf;
        while (--argc > 0) {
                if ((*++argv)[0]=='-' && (*argv)[1]=='\0' || fflg)
                        fi = 0;
                else {
                        if ((fi = open(*argv, 0)) < 0) {
                                if ( !silent )
                                        error(*argv);
                                continue;
                        }
                }
                while ((n = read(fi, ibuf, 512)) > 0) {
                        if(ubf) {
                                write(1, ibuf, n);
                                continue;
                        }
                        cpi = ibuf;
                        do {
                                if (cpo >= &obuf[512]) {
                                        write(1, obuf, 512);
                                        cpo = obuf;
                                }
                                *cpo++ = *cpi++;
                        } while (--n);
                }
                if (fi>0)
                        close(fi);
        }
        if (cpo > obuf)
                write(1, obuf, cpo-obuf);
        exit(0);
}

error(s)
{
        register char *cp;

        write(2, "cat: can't open ", 16);
        cp = s;
        while (*cp) {
                write(2, cp, 1);
                cp++;
        }
        write(2, "\n", 1);
}

badflag(s)
{
        register char *cp;

        write(2, "cat: bad flag ", 14);
        cp = s;
        while (*cp) {
                write(2, cp, 1);
                cp++;
        }
        write(2, "\n", 1);
}