miscutils/man.c

   1 /* mini man implementation for busybox
   2  * Copyright (C) 2008 Denys Vlasenko <vda.linux@googlemail.com>
   3  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   4  */
   5
   6 #include "libbb.h"
   7
   8 enum {
   9         OPT_a = 1, /* all */
  10         OPT_w = 2, /* print path */
  11 };
  12
  13 /* This is what I see on my desktop system being executed:
  14
  15 (
  16 echo ".ll 12.4i"
  17 echo ".nr LL 12.4i"
  18 echo ".pl 1100i"
  19 gunzip -c '/usr/man/man1/bzip2.1.gz'
  20 echo ".\\\""
  21 echo ".pl \n(nlu+10"
  22 ) | gtbl | nroff -Tlatin1 -mandoc | less
  23
  24 */
  25
  26 /* Trick gcc to reuse "cat" string. */
  27 #define STR_catNULmanNUL "cat\0man"
  28 #define STR_cat          "cat\0man"
  29
  30 //TODO: make gz/bz2 support conditional on FEATURE_SEAMLESS_GZ/BZ2,
  31 // add SEAMLESS_LZMA support
  32
  33 static int show_manpage(const char *pager, char *man_filename, int man, int level);
  34
  35 static int run_pipe(const char *unpacker, const char *pager, char *man_filename, int man, int level)
  36 {
  37         char *cmd;
  38
  39         /* Prevent man page link loops */
  40         if (level > 10)
  41                 return 0;
  42
  43         if (access(man_filename, R_OK) != 0)
  44                 return 0;
  45
  46         if (option_mask32 & OPT_w) {
  47                 puts(man_filename);
  48                 return 1;
  49         }
  50
  51         if (man) { /* man page, not cat page */
  52                 /* Test whether the man page is not a link to another one. */
  53                 /* The link has the following on the first line: */
  54                 /* ".so another_man_page" */
  55                 struct stat sb;
  56                 char *line;
  57                 char *linkname, *p;
  58
  59                 /* On my system:
  60                  * man1/genhostid.1.gz: 203 bytes - smallest real manpage
  61                  * man2/path_resolution.2.gz: 114 bytes - largest link
  62                  */
  63                 xstat(man_filename, &sb);
  64                 if (sb.st_size > 300) /* err on the safe side */
  65                         goto ordinary_manpage;
  66
  67                 line = xmalloc_open_zipped_read_close(man_filename, NULL);
  68                 if (!line || strncmp(line, ".so ", 4) != 0) {
  69                         free(line);
  70                         goto ordinary_manpage;
  71                 }
  72                 /* Example: man2/path_resolution.2.gz contains
  73                  * ".so man7/path_resolution.7\n<junk>"
  74                  */
  75                 *strchrnul(line, '\n') = '\0';
  76                 linkname = p = skip_whitespace(&line[4]);
  77
  78                 /* If link has no slashes, we just replace man page name.
  79                  * If link has slashes (however many), we go back *once*.
  80                  * ".so zzz/ggg/page.3" does NOT go back two levels. */
  81                 p = strrchr(man_filename, '/');
  82                 if (!p)
  83                         goto ordinary_manpage;
  84                 *p = '\0';
  85                 if (strchr(linkname, '/')) {
  86                         p = strrchr(man_filename, '/');
  87                         if (!p)
  88                                 goto ordinary_manpage;
  89                         *p = '\0';
  90                 }
  91
  92                 /* Links do not have .gz extensions, even if manpage
  93                  * is compressed */
  94                 man_filename = xasprintf("%s/%s" ".bz2", man_filename, linkname);
  95                 free(line);
  96                 /* Note: we leak "new" man_filename string as well... */
  97                 if (show_manpage(pager, man_filename, man, level + 1))
  98                         return 1;
  99                 /* else: show the link, it's better than nothing */
 100         }
 101
 102  ordinary_manpage:
 103         /* "2>&1" is added so that nroff errors are shown in pager too.
 104          * Otherwise it may show just empty screen */
 105         cmd = xasprintf(
 106                 man ? "%s '%s' 2>&1 | gtbl | nroff -Tlatin1 -mandoc 2>&1 | %s"
 107                     : "%s '%s' 2>&1 | %s",
 108                 unpacker, man_filename, pager);
 109         system(cmd);
 110         free(cmd);
 111         return 1;
 112 }
 113
 114 /* man_filename is of the form "/dir/dir/dir/name.s.bz2" */
 115 static int show_manpage(const char *pager, char *man_filename, int man, int level)
 116 {
 117         int len;
 118
 119         if (run_pipe("bunzip2 -c", pager, man_filename, man, level))
 120                 return 1;
 121
 122         len = strlen(man_filename) - 1;
 123
 124         man_filename[len] = '\0'; /* ".bz2" -> ".gz" */
 125         man_filename[len - 2] = 'g';
 126         if (run_pipe("gunzip -c", pager, man_filename, man, level))
 127                 return 1;
 128
 129         man_filename[len - 3] = '\0'; /* ".gz" -> "" */
 130         if (run_pipe(STR_cat, pager, man_filename, man, level))
 131                 return 1;
 132
 133         return 0;
 134 }
 135
 136 int man_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 137 int man_main(int argc UNUSED_PARAM, char **argv)
 138 {
 139         parser_t *parser;
 140         const char *pager;
 141         char **man_path_list;
 142         char *sec_list;
 143         char *cur_path, *cur_sect;
 144         int count_mp, cur_mp;
 145         int opt, not_found;
 146         char *token[2];
 147
 148         opt_complementary = "-1"; /* at least one argument */
 149         opt = getopt32(argv, "+aw");
 150         argv += optind;
 151
 152         sec_list = xstrdup("1:2:3:4:5:6:7:8:9");
 153         /* Last valid man_path_list[] is [0x10] */
 154         man_path_list = xzalloc(0x11 * sizeof(man_path_list[0]));
 155         count_mp = 0;
 156         man_path_list[0] = xstrdup(getenv("MANPATH"));
 157         if (man_path_list[0])
 158                 count_mp++;
 159         pager = getenv("MANPAGER");
 160         if (!pager) {
 161                 pager = getenv("PAGER");
 162                 if (!pager)
 163                         pager = "more";
 164         }
 165
 166         /* Parse man.conf */
 167         parser = config_open("/etc/man.conf");
 168         while (config_read(parser, token, 2, 0, "# \t", PARSE_NORMAL)) {
 169                 if (!token[1])
 170                         continue;
 171                 if (strcmp("MANPATH", token[0]) == 0) {
 172                         man_path_list = xrealloc_vector(man_path_list, 4, count_mp);
 173                         man_path_list[count_mp] = xstrdup(token[1]);
 174                         count_mp++;
 175                         /* man_path_list is NULL terminated */
 176                         /*man_path_list[count_mp] = NULL; - xrealloc_vector did it */
 177                 }
 178                 if (strcmp("MANSECT", token[0]) == 0) {
 179                         free(sec_list);
 180                         sec_list = xstrdup(token[1]);
 181                 }
 182         }
 183         config_close(parser);
 184
 185         not_found = 0;
 186         do { /* for each argv[] */
 187                 int found = 0;
 188                 cur_mp = 0;
 189                 while ((cur_path = man_path_list[cur_mp++]) != NULL) {
 190                         /* for each MANPATH */
 191                         do { /* for each MANPATH item */
 192                                 char *next_path = strchrnul(cur_path, ':');
 193                                 int path_len = next_path - cur_path;
 194                                 cur_sect = sec_list;
 195                                 do { /* for each section */
 196                                         char *next_sect = strchrnul(cur_sect, ':');
 197                                         int sect_len = next_sect - cur_sect;
 198                                         char *man_filename;
 199                                         int cat0man1 = 0;
 200
 201                                         /* Search for cat, then man page */
 202                                         while (cat0man1 < 2) {
 203                                                 int found_here;
 204                                                 man_filename = xasprintf("%.*s/%s%.*s/%s.%.*s" ".bz2",
 205                                                                 path_len, cur_path,
 206                                                                 STR_catNULmanNUL + cat0man1 * 4,
 207                                                                 sect_len, cur_sect,
 208                                                                 *argv,
 209                                                                 sect_len, cur_sect);
 210                                                 found_here = show_manpage(pager, man_filename, cat0man1, 0);
 211                                                 found |= found_here;
 212                                                 cat0man1 += found_here + 1;
 213                                                 free(man_filename);
 214                                         }
 215
 216                                         if (found && !(opt & OPT_a))
 217                                                 goto next_arg;
 218                                         cur_sect = next_sect;
 219                                         while (*cur_sect == ':')
 220                                                 cur_sect++;
 221                                 } while (*cur_sect);
 222                                 cur_path = next_path;
 223                                 while (*cur_path == ':')
 224                                         cur_path++;
 225                         } while (*cur_path);
 226                 }
 227                 if (!found) {
 228                         bb_error_msg("no manual entry for '%s'", *argv);
 229                         not_found = 1;
 230                 }
 231  next_arg:
 232                 argv++;
 233         } while (*argv);
 234
 235         return not_found;
 236 }