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

   1
   2 /*
   3  * arglist.c -- Routines for handling argument lists for execvp() and friends
   4  *
   5  * This code is Copyright (c) 2013, by the authors of nmh.  See the
   6  * COPYRIGHT file in the root directory of the nmh distribution for
   7  * complete copyright information.
   8  */
   9
  10 #include <h/mh.h>
  11 #include <h/utils.h>
  12
  13 /*
  14  * Split up a command into an appropriate array to pass to execvp()
  15  * or similar function.  Returns an allocated argv[] array.
  16  *
  17  * Function arguments:
  18  *
  19  * command - String to split up
  20  * file    - the first argument to "command", suitable for the first argument
  21  *           to execvp().  Returns allocated memory that must be free()d.
  22  * argp    - Index to last element (NULL) of returned argv[] array.
  23  *
  24  * Our basic algorithm is this:
  25  *
  26  * - If there are no spaces or shell metacharacters in "command", then
  27  *   take it as-is.
  28  * - If there are spaces in command, space-split command string.
  29  * - If we have shell metacharacters, run the command using
  30  *   /bin/sh -c 'command "$@"'.  In this case, any additional arguments
  31  *   appended to the arglist will be expanded by "$@".
  32  *
  33  * In all cases additional arguments can be added to the argv[] array.
  34  */
  35
  36 /* Shell metacharacters we use to trigger a call to the shell */
  37
  38 #define METACHARS       "$&*(){}[]'\";\\|?<>~`\n"
  39
  40 char **
  41 argsplit(char *command, char **file, int *argp)
  42 {
  43     char **argvarray, *p;
  44     int space = 0, metachar = 0, i;
  45
  46     for (p = command; *p; p++) {
  47         if (*p == ' ' || *p == '\t') {
  48                 space = 1;
  49         } else if (strchr(METACHARS, *p)) {
  50                 metachar = 1;
  51                 break;
  52         }
  53     }
  54
  55     argvarray = (char **) mh_xmalloc((sizeof(char **) * MAXARGS));
  56
  57     /*
  58      * The simple case - no spaces or shell metacharacters
  59      */
  60
  61     if (!space && !metachar) {
  62         argvarray[0] = getcpy(r1bindex(command, '/'));
  63         argvarray[1] = NULL;
  64         *file = getcpy(command);
  65         if (argp)
  66             *argp = 1;
  67         return argvarray;
  68     }
  69
  70     /*
  71      * Spaces, but no shell metacharacters; space-split into seperate
  72      * arguments
  73      */
  74
  75     if (space && !metachar) {
  76         char **split;
  77         p = getcpy(command);
  78         split = brkstring(p, " \t", NULL);
  79         if (split[0] == NULL) {
  80             adios(NULL, "Invalid blank command found");
  81         }
  82         argvarray[0] = getcpy(r1bindex(split[0], '/'));
  83         for (i = 1; split[i] != NULL; i++) {
  84             if (i > MAXARGS) {
  85                 adios(NULL, "Command exceeded argument limit");
  86             }
  87             argvarray[i] = getcpy(split[i]);
  88         }
  89         argvarray[i] = NULL;
  90         *file = getcpy(split[0]);
  91         if (argp)
  92             *argp = i;
  93         free(p);
  94         return argvarray;
  95     }
  96
  97     /*
  98      * Remaining option - pass to the shell.
  99      *
 100      * Some notes here:
 101      *
 102      * - The command passed to "sh -c" is actually:
 103      *      command "$@"
 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 $1.
 110      *   So we put in a dummy argument (we just use /bin/sh)
 111      */
 112
 113     *file = getcpy("/bin/sh");
 114     argvarray[0] = getcpy("sh");
 115     argvarray[1] = getcpy("-c");
 116     argvarray[2] = getcpy(command);
 117     argvarray[2] = add(" \"$@\"", argvarray[2]);
 118     argvarray[3] = getcpy("/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     if (command != NULL)
 137         free(command);
 138
 139     if (argvarray != NULL) {
 140         for (i = 0; argvarray[i] != NULL; i++)
 141             free(argvarray[i]);
 142         free(argvarray);
 143     }
 144 }