PostgreSQL的 initdb 源代码分析之九

继续：下面的是定义信号处理函数。

/*
* now we are starting to do real work, trap signals so we can clean up
*/

/* some of these are not valid on Windows */
#ifdef SIGHUP
pqsignal(SIGHUP, trapsig);
#endif
#ifdef SIGINT
pqsignal(SIGINT, trapsig);
#endif
#ifdef SIGQUIT
pqsignal(SIGQUIT, trapsig);
#endif
#ifdef SIGTERM
pqsignal(SIGTERM, trapsig);
#endif

#ifdef SIGPIPE
pqsignal(SIGPIPE, SIG_IGN);
#endif

SIGHUP： 我用 kill -HUP initdb的进程号，trapsig函数会收到 SIGHUP 信号，这是退出时候会收到的信号。

SIGINT: 我用 kill -INT initdb的进程号，trapsig函数会收到 SIGINT 信号，这是ctrl+c时会收到的信号。

SIGQUIT: ctrl+\ 时会受到的信号。

SIGTERM:

接下来：

switch (pg_check_dir(pg_data))
{
case 0:
/* PGDATA not there, must create it */
printf(_("creating directory %s ... "),
pg_data);
fflush(stdout);

if (!mkdatadir(NULL))
exit_nicely();
else
check_ok();

made_new_pgdata = true;
break;

case 1:
/* Present but empty, fix permissions and use it */
printf(_("fixing permissions on existing directory %s ... "),
pg_data);
fflush(stdout);

if (chmod(pg_data, S_IRWXU) != 0)
{
fprintf(stderr, _("%s: could not change permissions of directory \"%s\": %s\n"),
progname, pg_data, strerror(errno));
exit_nicely();
}
else
check_ok();

found_existing_pgdata = true;
break;

case 2:
/* Present and not empty */
fprintf(stderr,
_("%s: directory \"%s\" exists but is not empty\n"),
progname, pg_data);
fprintf(stderr,
_("If you want to create a new database system, either remove or empty\n"
"the directory \"%s\" or run %s\n"
"with an argument other than \"%s\".\n"),
pg_data, progname, pg_data);
exit(1);            /* no further message needed */

default:
/* Trouble accessing directory */
fprintf(stderr, _("%s: could not access directory \"%s\": %s\n"),
progname, pg_data, strerror(errno));
exit_nicely();
}

此时，要看这个函数的效果：

/*
* Test to see if a directory exists and is empty or not.
*
* Returns:
*        0 if nonexistent
*        1 if exists and empty
*        2 if exists and not empty
*        -1 if trouble accessing directory (errno reflects the error)
*/
int
pg_check_dir(const char *dir)
{
int            result = 1;
DIR           *chkdir;
struct dirent *file;

errno = 0;

chkdir = opendir(dir);

if (chkdir == NULL)
return (errno == ENOENT) ? 0 : -1;

while ((file = readdir(chkdir)) != NULL)
{
if (strcmp(".", file->d_name) == 0 ||
strcmp("..", file->d_name) == 0)
{
/* skip this and parent directory */
continue;
}
else
{
result = 2;            /* not empty */
break;
}
}

#ifdef WIN32

/*
* This fix is in mingw cvs (runtime/mingwex/dirent.c rev 1.4), but not in
* released version
*/
if (GetLastError() == ERROR_NO_MORE_FILES)
errno = 0;
#endif

closedir(chkdir);

if (errno != 0)
result = -1;            /* some kind of I/O error? */

return result;
}

按最正常的情况，我的目录存在而且为空，则 check_ok() 得到执行，而 found_existing_pgdata = true...