diplodocus.org Git - nmh/blob - sbr/arglist.c

   1 /* arglist.c -- Routines for handling argument lists for execvp() and friends
   2  *
   3  * This code is Copyright (c) 2013, by the authors of nmh.  See the
   4  * COPYRIGHT file in the root directory of the nmh distribution for
   5  * complete copyright information.
   6  */
   7
   8 #include <h/mh.h>
   9 #include <h/utils.h>
  10
  11 /*
  12  * Split up a command into an appropriate array to pass to execvp()
  13  * or similar function.  Returns an allocated argv[] array.
  14  *
  15  * Function arguments:
  16  *
  17  * command - String to split up
  18  * file    - the first argument to "command", suitable for the first argument
  19  *           to execvp().  Returns allocated memory that must be free()d.
  20  * argp    - Index to last element (NULL) of returned argv[] array.
  21  *
  22  * Our basic algorithm is this:
  23  *
  24  * - If there are no spaces or shell metacharacters in "command", then
  25  *   take it as-is.
  26  * - If there are spaces in command, space-split command string.
  27  * - If we have shell metacharacters, run the command using
  28  *   /bin/sh -c 'command "$@"'.  In this case, any additional arguments
  29  *   appended to the arglist will be expanded by "$@".
  30  *
  31  * In all cases additional arguments can be added to the argv[] array.
  32  */
  33
  34 /* Shell metacharacters we use to trigger a call to the shell */
  35
  36 #define METACHARS       "$&*(){}[]'\";\\|?<>~`\n"
  37
  38 char **
  39 argsplit(char *command, char **file, int *argp)
  40 {
  41     char **argvarray, *p;
  42     int i;
  43
  44     bool space = false;
  45     bool metachar = false;
  46     for (p = command; *p; p++) {
  47         if (*p == ' ' || *p == '\t') {
  48                 space = true;
  49         } else if (strchr(METACHARS, *p)) {
  50                 metachar = true;
  51                 break;
  52         }
  53     }
  54
  55     argvarray = mh_xmalloc(sizeof *argvarray * (MAXARGS + 5));
  56
  57     /*
  58      * The simple case - no spaces or shell metacharacters
  59      */
  60
  61     if (!space && !metachar) {
  62         argvarray[0] = mh_xstrdup(r1bindex(command, '/'));
  63         argvarray[1] = NULL;
  64         *file = mh_xstrdup(command);
  65         if (argp)
  66             *argp = 1;
  67         return argvarray;
  68     }
  69
  70     /*
  71      * Spaces, but no shell metacharacters; space-split into separate
  72      * arguments
  73      */
  74
  75     if (space && !metachar) {
  76         char **split;
  77         p = mh_xstrdup(command);
  78         split = brkstring(p, " \t", NULL);
  79         if (split[0] == NULL) {
  80             die("Invalid blank command found");
  81         }
  82         argvarray[0] = mh_xstrdup(r1bindex(split[0], '/'));
  83         for (i = 1; split[i] != NULL; i++) {
  84             if (i > MAXARGS) {
  85                 die("Command exceeded argument limit");
  86             }
  87             argvarray[i] = mh_xstrdup(split[i]);
  88         }
  89         argvarray[i] = NULL;
  90         *file = mh_xstrdup(split[0]);
  91         if (argp)
  92             *argp = i;
  93         free(p);
  94         return argvarray;
  95     }
  96
  97     /*
  98      * Remaining option - pass to the shell.
  99      *
 100      * Some notes here:
 101      *
 102      * - The command passed to "sh -c" is actually:
 103      *      command "$@"
 104      *
 105      *   If there are additional arguments they will be expanded by the
 106      *   shell, otherwise "$@" expands to nothing.
 107      *
 108      * - Every argument after the -c string gets put into positional
 109      *   parameters starting at $0, but $@ starts expanding with $1.
 110      *   So we put in a dummy argument (we just use /bin/sh)
 111      */
 112
 113     *file = mh_xstrdup("/bin/sh");
 114     argvarray[0] = mh_xstrdup("sh");
 115     argvarray[1] = mh_xstrdup("-c");
 116     argvarray[2] = mh_xstrdup(command);
 117     argvarray[2] = add(" \"$@\"", argvarray[2]);
 118     argvarray[3] = mh_xstrdup("/bin/sh");
 119     argvarray[4] = NULL;
 120
 121     if (argp)
 122         *argp = 4;
 123
 124     return argvarray;
 125 }
 126
 127 /*
 128  * Free our argument array
 129  */
 130
 131 void
 132 arglist_free(char *command, char **argvarray)
 133 {
 134     int i;
 135
 136     free(command);
 137
 138     if (argvarray != NULL) {
 139         for (i = 0; argvarray[i] != NULL; i++)
 140             free(argvarray[i]);
 141         free(argvarray);
 142     }
 143 }
 144
 145 /*
 146  * Similar in functionality to argsplit, but is designed to deal with
 147  * a msgs_array.
 148  */
 149
 150 void
 151 argsplit_msgarg(struct msgs_array *msgs, char *command, char **program)
 152 {
 153     int argp, i;
 154     char **vec;
 155
 156     vec = argsplit(command, program, &argp);
 157
 158     /*
 159      * As usual, there is lousy memory management in nmh.  Nothing ever
 160      * free's the msgs_array, and a lot of the arguments are allocated
 161      * from static memory.  I could have app_msgarg() allocate new
 162      * memory for each pointer, but for now I decided to stick with
 163      * the existing interface; maybe that will be revisited later.
 164      * So we'll just copy over our pointers and free the pointer list
 165      * (not the actual pointers themselves).  Note that we don't
 166      * include a trailing NULL, since we are expecting the application
 167      * to take care of that.
 168      */
 169
 170     for (i = 0; i < argp; i++) {
 171         app_msgarg(msgs, vec[i]);
 172     }
 173
 174     free(vec);
 175 }
 176
 177 /*
 178  * Insert a arglist vector into the beginning of an struct msgs array
 179  *
 180  * Uses by some programs (e.g., show) who want to decide which proc
 181  * to use after the argument vector has been constructed
 182  */
 183
 184 #ifndef MAXMSGS
 185 #define MAXMSGS 256
 186 #endif
 187
 188 void
 189 argsplit_insert(struct msgs_array *msgs, char *command, char **program)
 190 {
 191     int argp, i;
 192     char **vec;
 193
 194     vec = argsplit(command, program, &argp);
 195
 196     /*
 197      * Okay, we want to shuffle all of our arguments down so we have room
 198      * for argp number of arguments.  This means we need to know about
 199      * msgs_array internals.  If that changes, we need to change this
 200      * code here.
 201      */
 202
 203     if (msgs->size + argp >= msgs->max) {
 204         msgs->max += max(MAXMSGS, argp);
 205         msgs->msgs = mh_xrealloc(msgs->msgs, msgs->max * sizeof(*msgs->msgs));
 206     }
 207
 208     for (i = msgs->size - 1; i >= 0; i--)
 209         msgs->msgs[i + argp] = msgs->msgs[i];
 210
 211     msgs->size += argp;
 212
 213     /*
 214      * Now fill in the arguments at the beginning of the vector.
 215      */
 216
 217     for (i = 0; i < argp; i++)
 218         msgs->msgs[i] = vec[i];
 219
 220     free(vec);
 221 }