cmd/tail/tail.c

	tail.c revision 065da06d711716dc95a71a818ae0fb4479f31359
/*
 * Copyright (c) 1991, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Edward Sze-Tyan Wang.
 *
 * 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.
 * 4. 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/types.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "extern.h"

int Fflag, fflag, qflag, rflag, rval, no_files;

file_info_t *files;

static void obsolete(char **);
static void usage(void);

int
main(int argc, char *argv[])
{
    struct stat sb;
    const char *fn;
    FILE *fp;
    off_t off;
    enum STYLE style;
    int i, ch, first;
    file_info_t *file;
    char *p;

    /*
     * Tail's options are weird.  First, -n10 is the same as -n-10, not
     * -n+10.  Second, the number options are 1 based and not offsets,
     * so -n+1 is the first line, and -c-1 is the last byte.  Third, the
     * number options for the -r option specify the number of things that
     * get displayed, not the starting point in the file.  The one major
     * incompatibility in this version as compared to historical versions
     * is that the 'r' option couldn't be modified by the -lbc options,
     * i.e. it was always done in lines.  This version treats -rc as a
     * number of characters in reverse order.  Finally, the default for
     * -r is the entire file, not 10 lines.
     */
#define ARG(units, forward, backward) {                 \
    if (style)                          \
        usage();                        \
    off = strtoll(optarg, &p, 10) * (units);                        \
    if (*p)                             \
        errx(1, "illegal offset -- %s", optarg);        \
    switch (optarg[0]) {                        \
    case '+':                           \
        if (off)                        \
            off -= (units);                 \
            style = (forward);              \
        break;                          \
    case '-':                           \
        off = -off;                     \
        /* FALLTHROUGH */                   \
    default:                            \
        style = (backward);                 \
        break;                          \
    }                               \
}

    obsolete(argv);
    style = NOTSET;
    off = 0;
    while ((ch = getopt(argc, argv, "Fb:c:fn:qr")) != -1)
        switch (ch) {
        case 'F':   /* -F is superset of (and implies) -f */
            Fflag = fflag = 1;
            break;
        case 'b':
            ARG(512, FBYTES, RBYTES);
            break;
        case 'c':
            ARG(1, FBYTES, RBYTES);
            break;
        case 'f':
            fflag = 1;
            break;
        case 'n':
            ARG(1, FLINES, RLINES);
            break;
        case 'q':
            qflag = 1;
            break;
        case 'r':
            rflag = 1;
            break;
        case '?':
        default:
            usage();
        }
    argc -= optind;
    argv += optind;

    no_files = argc ? argc : 1;

    /*
     * If displaying in reverse, don't permit follow option, and convert
     * style values.
     */
    if (rflag) {
        if (fflag)
            usage();
        if (style == FBYTES)
            style = RBYTES;
        else if (style == FLINES)
            style = RLINES;
    }

    /*
     * If style not specified, the default is the whole file for -r, and
     * the last 10 lines if not -r.
     */
    if (style == NOTSET) {
        if (rflag) {
            off = 0;
            style = REVERSE;
        } else {
            off = 10;
            style = RLINES;
        }
    }

    if (*argv && fflag) {
        files = (struct file_info *)malloc(no_files *
            sizeof (struct file_info));
        if (!files)
            err(1, "Couldn't malloc space for file descriptors.");

        for (file = files; (fn = *argv++); file++) {
            file->file_name = strdup(fn);
            if (! file->file_name)
                errx(1, "Couldn't malloc space for file name.");
            if ((file->fp = fopen(file->file_name, "r")) == NULL ||
                fstat(fileno(file->fp), &file->st)) {
                if (file->fp != NULL) {
                    (void) fclose(file->fp);
                    file->fp = NULL;
                }
                if (!Fflag || errno != ENOENT)
                    ierr(file->file_name);
            }
        }
        follow(files, style, off);
        for (i = 0, file = files; i < no_files; i++, file++) {
            free(file->file_name);
        }
        free(files);
    } else if (*argv) {
        for (first = 1; (fn = *argv++); ) {
            if ((fp = fopen(fn, "r")) == NULL ||
                fstat(fileno(fp), &sb)) {
                ierr(fn);
                continue;
            }
            if (argc > 1 && !qflag) {
                (void) printf("%s==> %s <==\n",
                    first ? "" : "\n", fn);
                first = 0;
                (void) fflush(stdout);
            }

            if (rflag)
                reverse(fp, fn, style, off, &sb);
            else
                forward(fp, fn, style, off, &sb);
        }
    } else {
        fn = "stdin";

        if (fstat(fileno(stdin), &sb)) {
            ierr(fn);
            exit(1);
        }

        /*
         * Determine if input is a pipe.  4.4BSD will set the SOCKET
         * bit in the st_mode field for pipes.  Fix this then.
         */
        if (lseek(fileno(stdin), (off_t)0, SEEK_CUR) == -1 &&
            errno == ESPIPE) {
            errno = 0;
            fflag = 0;      /* POSIX.2 requires this. */
        }

        if (rflag)
            reverse(stdin, fn, style, off, &sb);
        else
            forward(stdin, fn, style, off, &sb);
    }
    exit(rval);
}

/*
 * Convert the obsolete argument form into something that getopt can handle.
 * This means that anything of the form [+-][0-9][0-9]*[lbc][Ffr] that isn't
 * the option argument for a -b, -c or -n option gets converted.
 */
static void
obsolete(char *argv[])
{
    char *ap, *p, *t;
    size_t len;
    char *start;

    while ((ap = *++argv)) {
        /* Return if "--" or not an option of any form. */
        if (ap[0] != '-') {
            if (ap[0] != '+')
                return;
        } else if (ap[1] == '-')
            return;

        switch (*++ap) {
        /* Old-style option. */
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':

            /* Malloc space for dash, new option and argument. */
            len = strlen(*argv);
            if ((start = p = malloc(len + 3)) == NULL)
                err(1, "malloc");
            *p++ = '-';

            /*
             * Go to the end of the option argument.  Save off any
             * trailing options (-3lf) and translate any trailing
             * output style characters.
             */
            t = *argv + len - 1;
            if (*t == 'F' || *t == 'f' || *t == 'r') {
                *p++ = *t;
                *t-- = '\0';
            }
            switch (*t) {
            case 'b':
                *p++ = 'b';
                *t = '\0';
                break;
            case 'c':
                *p++ = 'c';
                *t = '\0';
                break;
            case 'l':
                *t = '\0';
                /* FALLTHROUGH */
            case '0': case '1': case '2': case '3': case '4':
            case '5': case '6': case '7': case '8': case '9':
                *p++ = 'n';
                break;
            default:
                errx(1, "illegal option -- %s", *argv);
            }
            *p++ = *argv[0];
            (void) strcpy(p, ap);
            *argv = start;
            continue;

        /*
         * Legacy Solaris tail supports "+c" "-c", "+l", "-l",
         * "+b", and "-b" with an default number of 10.  Map
         * these arguments to an explicit +/-10 for FreeBSD.
         * New argument will be of the form -[bcn][+-]10
         */
        case 'b':
        case 'c':
        case 'l':
            if ((start = p = malloc(6)) == NULL)
                err(1, "malloc");
            *p++ = '-';
            switch (ap[0]) {
            case 'c':
                *p++ = ap[0];
                break;
            case 'b':
                *p++ = ap[0];
                break;
            case 'l':
                *p++ = 'n';
                break;
            }
            (void) snprintf(p, 6, "%c10", *argv[0]);
            *argv = start;

            continue;
        /*
         * Options w/ arguments, skip the argument and continue
         * with the next option.
         */
        case 'n':
            if (!ap[1])
                ++argv;
            /* FALLTHROUGH */
        /* Options w/o arguments, continue with the next option. */
        case 'F':
        case 'f':
        case 'r':
            continue;

        /* Illegal option, return and let getopt handle it. */
        default:
            return;
        }
    }
}

static void
usage(void)
{
    (void) fprintf(stderr,
        "usage: tail [-F | -f | -r] [-q] [-b # | -c # | -n #]"
        " [file ...]\n");
    exit(1);
}