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 :
/* 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 :
/* 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) != )
{
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 :
/* 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(); /* 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 = ;
DIR *chkdir;
struct dirent *file; errno = ; chkdir = opendir(dir); if (chkdir == NULL)
return (errno == ENOENT) ? : -; while ((file = readdir(chkdir)) != NULL)
{
if (strcmp(".", file->d_name) == ||
strcmp("..", file->d_name) == )
{
/* skip this and parent directory */
continue;
}
else
{
result = ; /* 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 = ;
#endif closedir(chkdir); if (errno != )
result = -; /* 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...