source: MondoRescue/branches/3.3/mindi-busybox/miscutils/man.c@ 3621

/* mini man implementation for busybox
 * Copyright (C) 2008 Denys Vlasenko <vda.linux@googlemail.com>
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

//usage:#define man_trivial_usage
//usage:       "[-aw] [MANPAGE]..."
//usage:#define man_full_usage "\n\n"
//usage:       "Format and display manual page\n"
//usage:     "\n    -a  Display all pages"
//usage:     "\n    -w  Show page locations"

#include "libbb.h"

enum {
    OPT_a = 1, /* all */
    OPT_w = 2, /* print path */
};

/* This is what I see on my desktop system being executed:

(
echo ".ll 12.4i"
echo ".nr LL 12.4i"
echo ".pl 1100i"
gunzip -c '/usr/man/man1/bzip2.1.gz'
echo ".\\\""
echo ".pl \n(nlu+10"
) | gtbl | nroff -Tlatin1 -mandoc | less

*/

static int show_manpage(const char *pager, char *man_filename, int man, int level);

static int run_pipe(const char *pager, char *man_filename, int man, int level)
{
    char *cmd;

    /* Prevent man page link loops */
    if (level > 10)
        return 0;

    if (access(man_filename, R_OK) != 0)
        return 0;

    if (option_mask32 & OPT_w) {
        puts(man_filename);
        return 1;
    }

    if (man) { /* man page, not cat page */
        /* Is this a link to another manpage? */
        /* The link has the following on the first line: */
        /* ".so another_man_page" */

        struct stat sb;
        char *line;
        char *linkname, *p;

        /* On my system:
         * man1/genhostid.1.gz: 203 bytes - smallest real manpage
         * man2/path_resolution.2.gz: 114 bytes - largest link
         */
        xstat(man_filename, &sb);
        if (sb.st_size > 300) /* err on the safe side */
            goto ordinary_manpage;

        line = xmalloc_open_zipped_read_close(man_filename, NULL);
        if (!line || !is_prefixed_with(line, ".so ")) {
            free(line);
            goto ordinary_manpage;
        }
        /* Example: man2/path_resolution.2.gz contains
         * ".so man7/path_resolution.7\n<junk>"
         */
        *strchrnul(line, '\n') = '\0';
        linkname = skip_whitespace(&line[4]);

        /* If link has no slashes, we just replace man page name.
         * If link has slashes (however many), we go back *once*.
         * ".so zzz/ggg/page.3" does NOT go back two levels. */
        p = strrchr(man_filename, '/');
        if (!p)
            goto ordinary_manpage;
        *p = '\0';
        if (strchr(linkname, '/')) {
            p = strrchr(man_filename, '/');
            if (!p)
                goto ordinary_manpage;
            *p = '\0';
        }

        /* Links do not have .gz extensions, even if manpage
         * is compressed */
        man_filename = xasprintf("%s/%s", man_filename, linkname);
        free(line);
        /* Note: we leak "new" man_filename string as well... */
        if (show_manpage(pager, man_filename, man, level + 1))
            return 1;
        /* else: show the link, it's better than nothing */
    }

 ordinary_manpage:
    close(STDIN_FILENO);
    open_zipped(man_filename, /*fail_if_not_compressed:*/ 0); /* guaranteed to use fd 0 (STDIN_FILENO) */
    /* "2>&1" is added so that nroff errors are shown in pager too.
     * Otherwise it may show just empty screen */
    cmd = xasprintf(
        /* replaced -Tlatin1 with -Tascii for non-UTF8 displays */
        man ? "gtbl | nroff -Tascii -mandoc 2>&1 | %s"
            : "%s",
        pager);
    system(cmd);
    free(cmd);
    return 1;
}

/* man_filename is of the form "/dir/dir/dir/name.s" */
static int show_manpage(const char *pager, char *man_filename, int man, int level)
{
#if SEAMLESS_COMPRESSION
    /* We leak this allocation... */
    char *filename_with_zext = xasprintf("%s.lzma", man_filename);
    char *ext = strrchr(filename_with_zext, '.') + 1;
#endif

#if ENABLE_FEATURE_SEAMLESS_LZMA
    if (run_pipe(pager, filename_with_zext, man, level))
        return 1;
#endif
#if ENABLE_FEATURE_SEAMLESS_XZ
    strcpy(ext, "xz");
    if (run_pipe(pager, filename_with_zext, man, level))
        return 1;
#endif
#if ENABLE_FEATURE_SEAMLESS_BZ2
    strcpy(ext, "bz2");
    if (run_pipe(pager, filename_with_zext, man, level))
        return 1;
#endif
#if ENABLE_FEATURE_SEAMLESS_GZ
    strcpy(ext, "gz");
    if (run_pipe(pager, filename_with_zext, man, level))
        return 1;
#endif

    return run_pipe(pager, man_filename, man, level);
}

static char **add_MANPATH(char **man_path_list, int *count_mp, char *path)
{
    if (path) while (*path) {
        char *next_path;
        char **path_element;

        next_path = strchr(path, ':');
        if (next_path) {
            if (next_path == path) /* "::"? */
                goto next;
            *next_path = '\0';
        }
        /* Do we already have path? */
        path_element = man_path_list;
        if (path_element) while (*path_element) {
            if (strcmp(*path_element, path) == 0)
                goto skip;
            path_element++;
        }
        man_path_list = xrealloc_vector(man_path_list, 4, *count_mp);
        man_path_list[*count_mp] = xstrdup(path);
        (*count_mp)++;
        /* man_path_list is NULL terminated */
        /* man_path_list[*count_mp] = NULL; - xrealloc_vector did it */
 skip:
        if (!next_path)
            break;
        /* "path" may be a result of getenv(), be nice and don't mangle it */
        *next_path = ':';
 next:
        path = next_path + 1;
    }
    return man_path_list;
}

int man_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int man_main(int argc UNUSED_PARAM, char **argv)
{
    parser_t *parser;
    const char *pager = ENABLE_LESS ? "less" : "more";
    char *sec_list;
    char *cur_path, *cur_sect;
    char **man_path_list;
    int count_mp;
    int cur_mp;
    int opt, not_found;
    char *token[2];

    opt_complementary = "-1"; /* at least one argument */
    opt = getopt32(argv, "+aw");
    argv += optind;

    sec_list = xstrdup("0p:1:1p:2:3:3p:4:5:6:7:8:9");

    count_mp = 0;
    man_path_list = add_MANPATH(NULL, &count_mp,
            getenv("MANDATORY_MANPATH"+10) /* "MANPATH" */
    );
    if (!man_path_list) {
        /* default, may be overridden by /etc/man.conf */
        man_path_list = xzalloc(2 * sizeof(man_path_list[0]));
        man_path_list[0] = (char*)"/usr/man";
        /* count_mp stays 0.
         * Thus, man.conf will overwrite man_path_list[0]
         * if a path is defined there.
         */
    }

    /* Parse man.conf[ig] or man_db.conf */
    /* man version 1.6f uses man.config */
    /* man-db implementation of man uses man_db.conf */
    parser = config_open2("/etc/man.config", fopen_for_read);
    if (!parser)
        parser = config_open2("/etc/man.conf", fopen_for_read);
    if (!parser)
        parser = config_open2("/etc/man_db.conf", fopen_for_read);

    while (config_read(parser, token, 2, 0, "# \t", PARSE_NORMAL)) {
        if (!token[1])
            continue;
        if (strcmp("DEFINE", token[0]) == 0) {
            if (is_prefixed_with("pager", token[1])) {
                pager = xstrdup(skip_whitespace(token[1]) + 5);
            }
        } else
        if (strcmp("MANDATORY_MANPATH"+10, token[0]) == 0 /* "MANPATH"? */
         || strcmp("MANDATORY_MANPATH", token[0]) == 0
        ) {
            man_path_list = add_MANPATH(man_path_list, &count_mp, token[1]);
        }
        if (strcmp("MANSECT", token[0]) == 0) {
            free(sec_list);
            sec_list = xstrdup(token[1]);
        }
    }
    config_close(parser);

    {
        /* environment overrides setting from man.config */
        char *env_pager = getenv("MANPAGER");
        if (!env_pager)
            env_pager = getenv("PAGER");
        if (env_pager)
            pager = env_pager;
    }

    not_found = 0;
    do { /* for each argv[] */
        int found = 0;
        cur_mp = 0;

        if (strchr(*argv, '/')) {
            found = show_manpage(pager, *argv, /*man:*/ 1, 0);
            goto check_found;
        }
        while ((cur_path = man_path_list[cur_mp++]) != NULL) {
            /* for each MANPATH */
            cur_sect = sec_list;
            do { /* for each section */
                char *next_sect = strchrnul(cur_sect, ':');
                int sect_len = next_sect - cur_sect;
                char *man_filename;
                int cat0man1 = 0;

                /* Search for cat, then man page */
                while (cat0man1 < 2) {
                    int found_here;
                    man_filename = xasprintf("%s/%s%.*s/%s.%.*s",
                            cur_path,
                            "cat\0man" + (cat0man1 * 4),
                            sect_len, cur_sect,
                            *argv,
                            sect_len, cur_sect);
                    found_here = show_manpage(pager, man_filename, cat0man1, 0);
                    found |= found_here;
                    cat0man1 += found_here + 1;
                    free(man_filename);
                }

                if (found && !(opt & OPT_a))
                    goto next_arg;
                cur_sect = next_sect;
                while (*cur_sect == ':')
                    cur_sect++;
            } while (*cur_sect);
        }
 check_found:
        if (!found) {
            bb_error_msg("no manual entry for '%s'", *argv);
            not_found = 1;
        }
 next_arg:
        argv++;
    } while (*argv);

    return not_found;
}