lib/command-line.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "command-line.h"
  19 #include <getopt.h>
  20 #include <limits.h>
  21 #include <stdlib.h>
  22 #include "util.h"
  23
  24 /* Given the GNU-style long options in 'options', returns a string that may be
  25  * passed to getopt() with the corresponding short options.  The caller is
  26  * responsible for freeing the string. */
  27 char *
  28 long_options_to_short_options(const struct option options[])
  29 {
  30     char short_options[UCHAR_MAX * 3 + 1];
  31     char *p = short_options;
  32
  33     for (; options->name; options++) {
  34         const struct option *o = options;
  35         if (o->flag == NULL && o->val > 0 && o->val <= UCHAR_MAX) {
  36             *p++ = o->val;
  37             if (o->has_arg == required_argument) {
  38                 *p++ = ':';
  39             } else if (o->has_arg == optional_argument) {
  40                 *p++ = ':';
  41                 *p++ = ':';
  42             }
  43         }
  44     }
  45     *p = '\0';
  46
  47     return xstrdup(short_options);
  48 }
  49
  50 /* Runs the command designated by argv[0] within the command table specified by
  51  * 'commands', which must be terminated by a command whose 'name' member is a
  52  * null pointer.
  53  *
  54  * Command-line options should be stripped off, so that a typical invocation
  55  * looks like "run_command(argc - optind, argv + optind, my_commands);". */
  56 void
  57 run_command(int argc, char *argv[], const struct command commands[])
  58 {
  59     const struct command *p;
  60
  61     if (argc < 1) {
  62         ovs_fatal(0, "missing command name; use --help for help");
  63     }
  64
  65     for (p = commands; p->name != NULL; p++) {
  66         if (!strcmp(p->name, argv[0])) {
  67             int n_arg = argc - 1;
  68             if (n_arg < p->min_args) {
  69                 ovs_fatal(0, "'%s' command requires at least %d arguments",
  70                           p->name, p->min_args);
  71             } else if (n_arg > p->max_args) {
  72                 ovs_fatal(0, "'%s' command takes at most %d arguments",
  73                           p->name, p->max_args);
  74             } else {
  75                 p->handler(argc, argv);
  76                 if (ferror(stdout)) {
  77                     ovs_fatal(0, "write to stdout failed");
  78                 }
  79                 if (ferror(stderr)) {
  80                     ovs_fatal(0, "write to stderr failed");
  81                 }
  82                 return;
  83             }
  84         }
  85     }
  86
  87     ovs_fatal(0, "unknown command '%s'; use --help for help", argv[0]);
  88 }
  89 \f
  90 /* Process title. */
  91
  92 #ifdef __linux__
  93 static char *argv_start;       /* Start of command-line arguments in memory. */
  94 static size_t argv_size;       /* Number of bytes of command-line arguments. */
  95 static char *saved_proctitle;  /* Saved command-line arguments. */
  96
  97 /* Prepares the process so that proctitle_set() can later succeed.
  98  *
  99  * This modifies the argv[] array so that it no longer points into the memory
 100  * that it originally does.  Later, proctitle_set() might overwrite that
 101  * memory.  That means that this function should be called before anything else
 102  * that accesses the process's argv[] array.  Ideally, it should be called
 103  * before anything else, period, at the very beginning of program
 104  * execution.  */
 105 void
 106 proctitle_init(int argc, char **argv)
 107 {
 108     int i;
 109
 110     if (!argc || !argv[0]) {
 111         /* This situation should never occur, but... */
 112         return;
 113     }
 114
 115     /* Specialized version of first loop iteration below. */
 116     argv_start = argv[0];
 117     argv_size = strlen(argv[0]) + 1;
 118     argv[0] = xstrdup(argv[0]);
 119
 120     for (i = 1; i < argc; i++) {
 121         size_t size = strlen(argv[i]) + 1;
 122
 123         /* Add (argv[i], strlen(argv[i])+1) to (argv_start, argv_size). */
 124         if (argv[i] + size == argv_start) {
 125             /* Arguments grow downward in memory. */
 126             argv_start -= size;
 127             argv_size += size;
 128         } else if (argv[i] == argv_start + argv_size) {
 129             /* Arguments grow upward in memory. */
 130             argv_size += size;
 131         } else {
 132             /* Arguments not contiguous.  (Is this really Linux?) */
 133         }
 134
 135         /* Copy out the old argument so we can reuse the space. */
 136         argv[i] = xstrdup(argv[i]);
 137     }
 138 }
 139
 140 /* Changes the name of the process, as shown by "ps", to 'format', which is
 141  * formatted as if by printf(). */
 142 void
 143 proctitle_set(const char *format, ...)
 144 {
 145     va_list args;
 146     int n;
 147
 148     if (!argv_start || argv_size < 8) {
 149         return;
 150     }
 151
 152     if (!saved_proctitle) {
 153         saved_proctitle = xmemdup(argv_start, argv_size);
 154     }
 155
 156     va_start(args, format);
 157     n = vsnprintf(argv_start, argv_size, format, args);
 158     if (n >= argv_size) {
 159         /* The name is too long, so add an ellipsis at the end. */
 160         strcpy(&argv_start[argv_size - 4], "...");
 161     } else {
 162         /* Fill the extra space with null bytes, so that trailing bytes don't
 163          * show up in the command line. */
 164         memset(&argv_start[n], '\0', argv_size - n);
 165     }
 166     va_end(args);
 167 }
 168
 169 /* Restores the process's original command line, as seen by "ps". */
 170 void
 171 proctitle_restore(void)
 172 {
 173     if (saved_proctitle) {
 174         memcpy(argv_start, saved_proctitle, argv_size);
 175         free(saved_proctitle);
 176         saved_proctitle = NULL;
 177     }
 178 }
 179 #else  /* !__linux__ */
 180 /* Stubs that don't do anything on non-Linux systems. */
 181
 182 void
 183 proctitle_init(int argc OVS_UNUSED, char **argv OVS_UNUSED)
 184 {
 185 }
 186
 187 void
 188 proctitle_set(const char *format OVS_UNUSED, ...)
 189 {
 190 }
 191
 192 void
 193 proctitle_restore(void)
 194 {
 195 }
 196 #endif  /* !__linux__ */