Re: head(1)

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Wed, Mar 31, 2010 at 09:34:51AM -0500, Andrew Ball wrote:
> I'm currently using NetBSD/i386-4.0.1 and I need to carve up a large
> file using head(1) and tail(1).  I am unable to do that because head
> seems only able to work on files of size up to around 2 Gbytes.

Try the attached version.

Joerg

/*      $NetBSD: head.c,v 1.21 2010/03/31 15:01:51 joerg Exp $  */

/*
 * Copyright (c) 1980, 1987, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1980, 1987, 1992, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)head.c      8.2 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: head.c,v 1.21 2010/03/31 15:01:51 joerg Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * head - give the first few lines of a stream or of each of a set of files
 *
 * Bill Joy UCB August 24, 1977
 */

static void head(FILE *, intmax_t, intmax_t);
static void obsolete(char *[]);
__dead static void usage(void);


int
main(int argc, char *argv[])
{
        int ch;
        FILE *fp;
        int first;
        uintmax_t linecnt;
        uintmax_t bytecnt;
        char *ep;
        int eval = 0;
        int qflag = 0;
        int vflag = 0;

        (void)setlocale(LC_ALL, "");
        obsolete(argv);
        linecnt = 10;
        bytecnt = 0;
        while ((ch = getopt(argc, argv, "c:n:qv")) != -1)
                switch(ch) {
                case 'c':
                        errno = 0;
                        bytecnt = strtoimax(optarg, &ep, 10);
                        if ((bytecnt == INTMAX_MAX && errno == ERANGE) ||
                            *ep || bytecnt <= 0)
                                err(1, "illegal byte count -- %s", optarg);
                        break;

                case 'n':
                        errno = 0;
                        linecnt = strtoimax(optarg, &ep, 10);
                        if ((linecnt == INTMAX_MAX && errno == ERANGE) ||
                            *ep || linecnt <= 0)
                                err(1, "illegal line count -- %s", optarg);
                        break;

                case 'q':
                        qflag = 1;
                        vflag = 0;
                        break;

                case 'v':
                        qflag = 0;
                        vflag = 1;
                        break;

                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (*argv)
                for (first = 1; *argv; ++argv) {
                        if ((fp = fopen(*argv, "r")) == NULL) {
                                warn("%s", *argv);
                                eval = 1;
                                continue;
                        }
                        if (vflag || (qflag == 0 && argc > 1)) {
                                (void)printf("%s==> %s <==\n",
                                    first ? "" : "\n", *argv);
                                first = 0;
                        }
                        head(fp, linecnt, bytecnt);
                        (void)fclose(fp);
                }
        else
                head(stdin, linecnt, bytecnt);
        exit(eval);
}

static void
head(FILE *fp, intmax_t cnt, intmax_t bytecnt)
{
        char buf[65536];
        size_t len, rv, rv2;
        int ch;

        if (bytecnt) {
                while (bytecnt) {
                        len = sizeof(buf);
                        if (bytecnt > (intmax_t)sizeof(buf))
                                len = sizeof(buf);
                        else
                                len = bytecnt;
                        rv = fread(buf, 1, len, fp);
                        if (rv == 0)
                                break; /* Distinguish EOF and error? */
                        rv2 = fwrite(buf, 1, rv, stdout);
                        if (rv2 != rv) {
                                if (feof(stdout))
                                        errx(1, "EOF on stdout");
                                else
                                        err(1, "failure writing to stdout");
                        }
                        bytecnt -= rv;
                }
        } else {
                while ((ch = getc(fp)) != EOF) {
                        if (putchar(ch) == EOF)
                                err(1, "stdout");
                        if (ch == '\n' && --cnt == 0)
                                break;
                }
        }
}

static void
obsolete(char *argv[])
{
        char *ap;

        while ((ap = *++argv)) {
                /* Return if "--" or not "-[0-9]*". */
                if (ap[0] != '-' || ap[1] == '-' ||
                    !isdigit((unsigned char)ap[1]))
                        return;
                if ((ap = malloc(strlen(*argv) + 2)) == NULL)
                        err(1, NULL);
                ap[0] = '-';
                ap[1] = 'n';
                (void)strcpy(ap + 2, *argv + 1);
                *argv = ap;
        }
}

static void
usage(void)
{

        (void)fprintf(stderr, "usage: %s [-n lines] [file ...]\n",
            getprogname());
        exit(1);
}