Function do_edit

src/bin/psql/command.c:3813–3994

* do_edit -- handler for \e * * If you do not specify a filename, the current query buffer will be copied * into a temporary file. * * After this function is done, the resulting file will be copied back into the * query buffer. As an exception to this, the query buffer will be emptied * if the file was not modified (or the editor failed) and the caller passes * "discard_on_quit" = true.

 * is successfully replaced.
 */
static bool
do_edit(const char *filename_arg, PQExpBuffer query_buf,
		int lineno, bool discard_on_quit, bool *edited)
{
	char		fnametmp[MAXPGPATH];
	FILE	   *stream = NULL;
	const char *fname;
	bool		error = false;
	int			fd;
	struct stat before,
				after;

	if (filename_arg)
		fname = filename_arg;
	else
	{
		/* make a temp file to edit */
#ifndef WIN32
		const char *tmpdir = getenv("TMPDIR");

		if (!tmpdir)
			tmpdir = "/tmp";
#else
		char		tmpdir[MAXPGPATH];
		int			ret;

		ret = GetTempPath(MAXPGPATH, tmpdir);
		if (ret == 0 || ret > MAXPGPATH)
		{
			pg_log_error("could not locate temporary directory: %s",
						 !ret ? strerror(errno) : "");
			return false;
		}
#endif

		/*
		 * No canonicalize_path() here. EDIT.EXE run from CMD.EXE prepends the
		 * current directory to the supplied path unless we use only
		 * backslashes, so we do that.
		 */
#ifndef WIN32
		snprintf(fnametmp, sizeof(fnametmp), "%s%spsql.edit.%d.sql", tmpdir,
				 "/", (int) getpid());
#else
		snprintf(fnametmp, sizeof(fnametmp), "%s%spsql.edit.%d.sql", tmpdir,
				 "" /* trailing separator already present */ , (int) getpid());
#endif

		fname = (const char *) fnametmp;

		fd = open(fname, O_WRONLY | O_CREAT | O_EXCL, 0600);
		if (fd != -1)
			stream = fdopen(fd, "w");

		if (fd == -1 || !stream)
		{
			pg_log_error("could not open temporary file \"%s\": %m", fname);
			error = true;