Function psql_get_variable

src/bin/psql/common.c:128–213

* Variable-fetching callback for flex lexer * * If the specified variable exists, return its value as a string (malloc'd * and expected to be freed by the caller); else return NULL. * * If "quote" isn't PQUOTE_PLAIN, then return the value suitably quoted and * escaped for the specified quoting requirement. (Failure in escaping * should lead to printing an error and returning NULL.) * * "

 * determine whether variable expansion is allowed.
 */
char *
psql_get_variable(const char *varname, PsqlScanQuoteType quote,
				  void *passthrough)
{
	char	   *result = NULL;
	const char *value;

	/* In an inactive \if branch, suppress all variable substitutions */
	if (passthrough && !conditional_active((ConditionalStack) passthrough))
		return NULL;

	value = GetVariable(pset.vars, varname);
	if (!value)
		return NULL;

	switch (quote)
	{
		case PQUOTE_PLAIN:
			result = pg_strdup(value);
			break;
		case PQUOTE_SQL_LITERAL:
		case PQUOTE_SQL_IDENT:
			{
				/*
				 * For these cases, we use libpq's quoting functions, which
				 * assume the string is in the connection's client encoding.
				 */
				char	   *escaped_value;

				if (!pset.db)
				{
					pg_log_error("cannot escape without active connection");
					return NULL;
				}

				if (quote == PQUOTE_SQL_LITERAL)
					escaped_value =
						PQescapeLiteral(pset.db, value, strlen(value));
				else
					escaped_value =
						PQescapeIdentifier(pset.db, value, strlen(value));

				if (escaped_value == NULL)
				{
					const char *error = PQerrorMessage(pset.db);

					pg_log_info("%s", error);
					return NULL;
				}

				/*
				 * Rather than complicate the lexer's API with a notion of
				 * which free() routine to use, just pay the price of an extra
				 * strdup().
				 */
				result = pg_strdup(escaped_value);
				PQfreemem(escaped_value);
				break;