source: MondoRescue/branches/3.3/mindi-busybox/coreutils/head.c@ 3647

/* vi: set sw=4 ts=4: */
/*
 * head implementation for busybox
 *
 * Copyright (C) 2003  Manuel Novoa III  <mjn3@codepoet.org>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/* BB_AUDIT SUSv3 compliant */
/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/head.html */

//kbuild:lib-$(CONFIG_HEAD) += head.o

//usage:#define head_trivial_usage
//usage:       "[OPTIONS] [FILE]..."
//usage:#define head_full_usage "\n\n"
//usage:       "Print first 10 lines of each FILE (or stdin) to stdout.\n"
//usage:       "With more than one FILE, precede each with a filename header.\n"
//usage:     "\n    -n N[kbm]   Print first N lines"
//usage:    IF_FEATURE_FANCY_HEAD(
//usage:     "\n    -n -N[kbm]  Print all except N last lines"
//usage:     "\n    -c [-]N[kbm]    Print first N bytes"
//usage:     "\n    -q      Never print headers"
//usage:     "\n    -v      Always print headers"
//usage:    )
//usage:     "\n"
//usage:     "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
//usage:
//usage:#define head_example_usage
//usage:       "$ head -n 2 /etc/passwd\n"
//usage:       "root:x:0:0:root:/root:/bin/bash\n"
//usage:       "daemon:x:1:1:daemon:/usr/sbin:/bin/sh\n"

#include "libbb.h"

/* This is a NOEXEC applet. Be very careful! */

#if !ENABLE_FEATURE_FANCY_HEAD
# define print_first_N(fp,count,bytes) print_first_N(fp,count)
#endif
static void
print_first_N(FILE *fp, unsigned long count, bool count_bytes)
{
#if !ENABLE_FEATURE_FANCY_HEAD
    const int count_bytes = 0;
#endif
    while (count) {
        int c = getc(fp);
        if (c == EOF)
            break;
        if (count_bytes || (c == '\n'))
            --count;
        putchar(c);
    }
}

#if ENABLE_FEATURE_FANCY_HEAD
static void
print_except_N_last_bytes(FILE *fp, unsigned count)
{
    unsigned char *circle = xmalloc(++count);
    unsigned head = 0;
    for(;;) {
        int c;
        c = getc(fp);
        if (c == EOF)
            goto ret;
        circle[head++] = c;
        if (head == count)
            break;
    }
    for (;;) {
        int c;
        if (head == count)
            head = 0;
        putchar(circle[head]);
        c = getc(fp);
        if (c == EOF)
            goto ret;
        circle[head] = c;
        head++;
    }
 ret:
    free(circle);
}

static void
print_except_N_last_lines(FILE *fp, unsigned count)
{
    char **circle = xzalloc((++count) * sizeof(circle[0]));
    unsigned head = 0;
    for(;;) {
        char *c;
        c = xmalloc_fgets(fp);
        if (!c)
            goto ret;
        circle[head++] = c;
        if (head == count)
            break;
    }
    for (;;) {
        char *c;
        if (head == count)
            head = 0;
        fputs(circle[head], stdout);
        c = xmalloc_fgets(fp);
        if (!c)
            goto ret;
        free(circle[head]);
        circle[head++] = c;
    }
 ret:
    head = 0;
    for(;;) {
        free(circle[head++]);
        if (head == count)
            break;
    }
    free(circle);
}
#else
/* Must never be called */
void print_except_N_last_bytes(FILE *fp, unsigned count);
void print_except_N_last_lines(FILE *fp, unsigned count);
#endif

#if !ENABLE_FEATURE_FANCY_HEAD
# define eat_num(negative_N,p) eat_num(p)
#endif
static unsigned long
eat_num(bool *negative_N, const char *p)
{
#if ENABLE_FEATURE_FANCY_HEAD
    if (*p == '-') {
        *negative_N = 1;
        p++;
    }
#endif
    return xatoul_sfx(p, bkm_suffixes);
}

static const char head_opts[] ALIGN1 =
    "n:"
#if ENABLE_FEATURE_FANCY_HEAD
    "c:qv"
#endif
    ;

#define header_fmt_str "\n==> %s <==\n"

int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int head_main(int argc, char **argv)
{
    unsigned long count = 10;
#if ENABLE_FEATURE_FANCY_HEAD
    int header_threshhold = 1;
    bool count_bytes = 0;
    bool negative_N = 0;
#else
# define header_threshhold 1
# define count_bytes       0
# define negative_N        0
#endif
    FILE *fp;
    const char *fmt;
    char *p;
    int opt;
    int retval = EXIT_SUCCESS;

#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
    /* Allow legacy syntax of an initial numeric option without -n. */
    if (argv[1] && argv[1][0] == '-'
     && isdigit(argv[1][1])
    ) {
        --argc;
        ++argv;
        p = argv[0] + 1;
        goto GET_COUNT;
    }
#endif

    /* No size benefit in converting this to getopt32 */
    while ((opt = getopt(argc, argv, head_opts)) > 0) {
        switch (opt) {
#if ENABLE_FEATURE_FANCY_HEAD
        case 'q':
            header_threshhold = INT_MAX;
            break;
        case 'v':
            header_threshhold = -1;
            break;
        case 'c':
            count_bytes = 1;
            /* fall through */
#endif
        case 'n':
            p = optarg;
#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
 GET_COUNT:
#endif
            count = eat_num(&negative_N, p);
            break;
        default:
            bb_show_usage();
        }
    }

    argc -= optind;
    argv += optind;
    if (!*argv)
        *--argv = (char*)"-";

    fmt = header_fmt_str + 1;
    if (argc <= header_threshhold) {
#if ENABLE_FEATURE_FANCY_HEAD
        header_threshhold = 0;
#else
        fmt += 11; /* "" */
#endif
    }
    if (negative_N) {
        if (count >= INT_MAX / sizeof(char*))
            bb_error_msg("count is too big: %lu", count);
    }

    do {
        fp = fopen_or_warn_stdin(*argv);
        if (fp) {
            if (fp == stdin) {
                *argv = (char *) bb_msg_standard_input;
            }
            if (header_threshhold) {
                printf(fmt, *argv);
            }
            if (negative_N) {
                if (count_bytes) {
                    print_except_N_last_bytes(fp, count);
                } else {
                    print_except_N_last_lines(fp, count);
                }
            } else {
                print_first_N(fp, count, count_bytes);
            }
            die_if_ferror_stdout();
            if (fclose_if_not_stdin(fp)) {
                bb_simple_perror_msg(*argv);
                retval = EXIT_FAILURE;
            }
        } else {
            retval = EXIT_FAILURE;
        }
        fmt = header_fmt_str;
    } while (*++argv);

    fflush_stdout_and_exit(retval);
}