source: MondoRescue/branches/3.2/mindi-busybox/coreutils/head.c@ 3263

/* 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 */

//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    -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! */

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

static const struct suffix_mult head_suffixes[] = {
    { "b", 512 },
    { "k", 1024 },
    { "m", 1024*1024 },
    { "", 0 }
};

#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;
    unsigned long i;
#if ENABLE_FEATURE_FANCY_HEAD
    int count_bytes = 0;
    int header_threshhold = 1;
#endif
    FILE *fp;
    const char *fmt;
    char *p;
    int opt;
    int c;
    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) + 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 = xatoul_sfx(p, head_suffixes);
            break;
        default:
            bb_show_usage();
        }
    }

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

    fmt = header_fmt_str + 1;
#if ENABLE_FEATURE_FANCY_HEAD
    if (argc <= header_threshhold) {
        header_threshhold = 0;
    }
#else
    if (argc <= 1) {
        fmt += 11; /* "" */
    }
    /* Now define some things here to avoid #ifdefs in the code below.
     * These should optimize out of the if conditions below. */
#define header_threshhold   1
#define count_bytes         0
#endif

    do {
        fp = fopen_or_warn_stdin(*argv);
        if (fp) {
            if (fp == stdin) {
                *argv = (char *) bb_msg_standard_input;
            }
            if (header_threshhold) {
                printf(fmt, *argv);
            }
            i = count;
            while (i && ((c = getc(fp)) != EOF)) {
                if (count_bytes || (c == '\n')) {
                    --i;
                }
                putchar(c);
            }
            if (fclose_if_not_stdin(fp)) {
                bb_simple_perror_msg(*argv);
                retval = EXIT_FAILURE;
            }
            die_if_ferror_stdout();
        } else {
            retval = EXIT_FAILURE;
        }
        fmt = header_fmt_str;
    } while (*++argv);

    fflush_stdout_and_exit(retval);
}