lib/dpkg/command.c

   1 /*
   2  * libdpkg - Debian packaging suite library routines
   3  * command.c - command execution support
   4  *
   5  * Copyright © 2010-2012 Guillem Jover <guillem@debian.org>
   6  *
   7  * This is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <config.h>
  22 #include <compat.h>
  23
  24 #include <stdarg.h>
  25 #include <stdlib.h>
  26 #include <unistd.h>
  27
  28 #include <dpkg/dpkg.h>
  29 #include <dpkg/i18n.h>
  30 #include <dpkg/string.h>
  31 #include <dpkg/varbuf.h>
  32 #include <dpkg/file.h>
  33 #include <dpkg/path.h>
  34 #include <dpkg/command.h>
  35
  36 /**
  37  * Initialize a command structure.
  38  *
  39  * If name is NULL, then the last component of the filename path will be
  40  * used to initialize the name member.
  41  *
  42  * @param cmd The command structure to initialize.
  43  * @param filename The filename of the command to execute.
  44  * @param name The description of the command to execute.
  45  */
  46 void
  47 command_init(struct command *cmd, const char *filename, const char *name)
  48 {
  49         cmd->filename = filename;
  50         if (name == NULL)
  51                 cmd->name = path_basename(filename);
  52         else
  53                 cmd->name = name;
  54         cmd->argc = 0;
  55         cmd->argv_size = 10;
  56         cmd->argv = m_malloc(cmd->argv_size * sizeof(cmd->argv[0]));
  57         cmd->argv[0] = NULL;
  58 }
  59
  60 /**
  61  * Destroy a command structure.
  62  *
  63  * Free the members managed by the command functions (i.e. the argv pointer
  64  * array), and zero all members of a command structure.
  65  *
  66  * @param cmd The command structure to free.
  67  */
  68 void
  69 command_destroy(struct command *cmd)
  70 {
  71         cmd->filename = NULL;
  72         cmd->name = NULL;
  73         cmd->argc = 0;
  74         cmd->argv_size = 0;
  75         free(cmd->argv);
  76         cmd->argv = NULL;
  77 }
  78
  79 static void
  80 command_grow_argv(struct command *cmd, int need)
  81 {
  82         /* We need a ghost byte for the NUL character. */
  83         need++;
  84
  85         /* Check if we already have enough room. */
  86         if ((cmd->argv_size - cmd->argc) >= need)
  87                 return;
  88
  89         cmd->argv_size = (cmd->argv_size + need) * 2;
  90         cmd->argv = m_realloc(cmd->argv, cmd->argv_size * sizeof(cmd->argv[0]));
  91 }
  92
  93 /**
  94  * Append an argument to the command's argv.
  95  *
  96  * @param cmd The command structure to act on.
  97  * @param arg The argument to append to argv.
  98  */
  99 void
 100 command_add_arg(struct command *cmd, const char *arg)
 101 {
 102         command_grow_argv(cmd, 1);
 103
 104         cmd->argv[cmd->argc++] = arg;
 105         cmd->argv[cmd->argc] = NULL;
 106 }
 107
 108 /**
 109  * Append an argument array to the command's argv.
 110  *
 111  * @param cmd The command structure to act on.
 112  * @param argv The NULL terminated argument array to append to argv.
 113  */
 114 void
 115 command_add_argl(struct command *cmd, const char **argv)
 116 {
 117         int i, add_argc = 0;
 118
 119         while (argv[add_argc] != NULL)
 120                 add_argc++;
 121
 122         command_grow_argv(cmd, add_argc);
 123
 124         for (i = 0; i < add_argc; i++)
 125                 cmd->argv[cmd->argc++] = argv[i];
 126
 127         cmd->argv[cmd->argc] = NULL;
 128 }
 129
 130 /**
 131  * Append a va_list of argument to the command's argv.
 132  *
 133  * @param cmd The command structure to act on.
 134  * @param args The NULL terminated va_list of argument array to append to argv.
 135  */
 136 void
 137 command_add_argv(struct command *cmd, va_list args)
 138 {
 139         va_list args_copy;
 140         int i, add_argc = 0;
 141
 142         va_copy(args_copy, args);
 143         while (va_arg(args_copy, const char *) != NULL)
 144                 add_argc++;
 145         va_end(args_copy);
 146
 147         command_grow_argv(cmd, add_argc);
 148
 149         for (i = 0; i < add_argc; i++)
 150                 cmd->argv[cmd->argc++] = va_arg(args, const char *);
 151
 152         cmd->argv[cmd->argc] = NULL;
 153 }
 154
 155 /**
 156  * Append a variable list of argument to the command's argv.
 157  *
 158  * @param cmd The command structure to act on.
 159  * @param ... The NULL terminated variable list of argument to append to argv.
 160  */
 161 void
 162 command_add_args(struct command *cmd, ...)
 163 {
 164         va_list args;
 165
 166         va_start(args, cmd);
 167         command_add_argv(cmd, args);
 168         va_end(args);
 169 }
 170
 171 /**
 172  * Execute the command specified.
 173  *
 174  * The command is executed searching the PATH if the filename does not
 175  * contain any slashes, or using the full path if it's either a relative or
 176  * absolute pathname. This functions does not return.
 177  *
 178  * @param cmd The command structure to act on.
 179  */
 180 void
 181 command_exec(struct command *cmd)
 182 {
 183         execvp(cmd->filename, (char * const *)cmd->argv);
 184         ohshite(_("unable to execute %s (%s)"), cmd->name, cmd->filename);
 185 }
 186
 187 /**
 188  * Execute a shell with a possible command.
 189  *
 190  * @param cmd The command string to execute, if it's NULL an interactive
 191  *            shell will be executed instead.
 192  * @param name The description of the command to execute.
 193  */
 194 void
 195 command_shell(const char *cmd, const char *name)
 196 {
 197         const char *shell;
 198         const char *mode;
 199
 200         if (cmd == NULL) {
 201                 mode = "-i";
 202                 shell = getenv("SHELL");
 203         } else {
 204                 mode = "-c";
 205                 shell = NULL;
 206         }
 207
 208         if (str_is_unset(shell))
 209                 shell = DPKG_DEFAULT_SHELL;
 210
 211         execlp(shell, shell, mode, "--", cmd, NULL);
 212         ohshite(_("unable to execute %s (%s)"), name, cmd);
 213 }
 214
 215 /**
 216  * Check whether a command can be found in PATH.
 217  *
 218  * @param cmd The command name to check. This is a relative pathname.
 219  *
 220  * @return A boolean denoting whether the command has been found.
 221  */
 222 bool
 223 command_in_path(const char *cmd)
 224 {
 225         struct varbuf filename = VARBUF_INIT;
 226         const char *path_list;
 227         const char *path, *path_end;
 228
 229         if (cmd[0] == '/')
 230                 return file_is_exec(cmd);
 231
 232         path_list = getenv("PATH");
 233         if (!path_list)
 234                 ohshit(_("PATH is not set"));
 235
 236         for (path = path_list; path; path = *path_end ? path_end + 1 : NULL) {
 237                 size_t path_len;
 238
 239                 path_end = strchrnul(path, ':');
 240                 path_len = (size_t)(path_end - path);
 241
 242                 varbuf_set_buf(&filename, path, path_len);
 243                 if (path_len)
 244                         varbuf_add_char(&filename, '/');
 245                 varbuf_add_str(&filename, cmd);
 246                 varbuf_end_str(&filename);
 247
 248                 if (file_is_exec(filename.buf)) {
 249                         varbuf_destroy(&filename);
 250                         return true;
 251                 }
 252         }
 253
 254         varbuf_destroy(&filename);
 255         return false;
 256 }