继续
其实接前面，整个while循环是这样的：
while ((c = getopt_long(argc, argv, "dD:E:L:nU:WA:sT:X:", long_options, &option_index)) != -)
{
switch (c)
{
......
} ......
}
这一句，c = getopt_long(argc, argv, "dD:E:L:nU:WA:sT:X:", long_options, &option_index)，
除了获得initdb 后跟着的是 -D 还是 -E之类的，还有一个用途，就是给 全局变量 optarg 赋值。这个全局变量其实挺坑爹的。
/*
* getopt_long
* Parse argc/argv argument vector, with long options.
*
* This implementation does not use optreset. Instead, we guarantee that
* it can be restarted on a new argv array after a previous call returned -1,
* if the caller resets optind to 1 before the first call of the new series.
* (Internally, this means we must be sure to reset "place" to EMSG before
* returning -1.)
*/
int
getopt_long(int argc, char *const argv[],
const char *optstring,
const struct option * longopts, int *longindex)
{
......
if (!*place)
{ /* update scanning pointer */
...... if (place[] && place[] == '-' && place[])
{
......for (i = ; longopts[i].name != NULL; i++)
{
if (strlen(longopts[i].name) == namelen
&& strncmp(place, longopts[i].name, namelen) == )
{
if (longopts[i].has_arg)
{
if (place[namelen] == '=')
optarg = place + namelen + ;
else if (optind < argc - )
{
optind++;
optarg = argv[optind];
}
else
{
......
}
}
else
{
......
} ......
}
}
......
}
} ...... if (oli[] != ':')
{ /* don't need argument */ ......
}
else
{ /* need an argument */
if (*place) /* no white space */
optarg = place;
else if (argc <= ++optind)
{ /* no arg */ ......
}
else
/* white space */
optarg = argv[optind];
place = EMSG;
++optind;
}
return optopt;
}
我经过运行，得到的是：
optarg 变量的值为 /home/pgsql/DemoDir。
通过下面的代码，pg_data 被赋值为 /home/pgsql/DemoDir。
/* process command-line options */
while ((c = getopt_long(argc, argv, "dD:E:L:nU:WA:sT:X:", long_options, &option_index)) != -)
{
switch (c)
{
case 'A':
authmethod = xstrdup(optarg);
break;
case 'D':
pg_data = xstrdup(optarg);
break;
......
}
......
}
继续分析。
main函数的下一段，其中的 optiond，也是由前面的 getopt_long 函数计算出来的，我运行时候，其值为 3。
如下代码，是异常处理，可以跳过。
if (optind < argc)
{
pg_data = xstrdup(argv[optind]);
optind++;
}
if (optind < argc)
{
fprintf(stderr, _("%s: too many command-line arguments (first is \"%s\")\n"),
progname, argv[optind + ]);
fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
progname);
exit();
}