usr/strings.c


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#include "gbos.h"
/* strings [-n N] [file]: print runs of N or more printable characters
 * (default 4). Pairs with xxd now that /bin/<prog> is readable - it is how
 * you find the text baked into a program image. */

#define MAXRUN 64

void main(void) {
    char *argv[8];
    char run[MAXRUN];
    unsigned char argc = argv_parse(argv, 8);
    char *nv = optval(argv, argc, 'n');
    unsigned char min = nv ? atou(nv) : 4;
    unsigned char len = 0, fd = NOFD, i;
    char *fname = 0;
    int ch;

    if (min == 0) min = 4;
    if (min > MAXRUN) min = MAXRUN;
    for (i = 0; i < argc; i++) {
        if (argv[i][0] == '-') continue;
        if (nv == argv[i]) continue;
        fname = argv[i];
        break;
    }
    if (fname) {
        fd = open(fname, O_READ);
        if (fd == EISDIR) {
            puts("strings: is a directory");
            nl();
            sexit(2);
        }
        if (fd == NOFD) {
            puts("strings: no such file");
            nl();
            sexit(2);
        }
    }
    for (;;) {
        if (fd == NOFD) {
            char c = readc();
            ch = (c == EOF) ? -1 : c;
        } else ch = fgetc(fd);
        if (ch >= 32 && ch < 127) {
            if (len < MAXRUN) run[len++] = (char)ch;
            continue;
        }
        if (len >= min) {
            writes(run, len);
            nl();
        } /* run ended: keep it? */
        len = 0;
        if (ch < 0) break;
    }
    if (len >= min) {
        writes(run, len);
        nl();
    }
    if (fd != NOFD) close(fd);
}