Do not store result on bc/calc errors

README.md

@@ -1,8 +1,8 @@
 <h1 align="center">bcal</h1>
 
 <p align="center">
-<a href="https://github.com/jarun/bcal/releases/latest"><img src="https://img.shields.io/github/release/jarun/bcal.svg?maxAge=600" alt="Latest release" /></a>
-<a href="https://repology.org/project/bcal/versions"><img src="https://repology.org/badge/tiny-repos/bcal.svg" alt="Availability"></a>
+<a href="https://github.com/jarun/bcal/releases/latest"><img src="https://img.shields.io/github/release/jarun/bcal.svg?maxAge=600&label=rel" alt="Latest release" /></a>
+<a href="https://repology.org/project/bcal/versions"><img src="https://repology.org/badge/tiny-repos/bcal.svg?header=repos" alt="Availability"></a>
 <a href="https://circleci.com/gh/jarun/workflows/bcal"><img src="https://img.shields.io/circleci/project/github/jarun/bcal.svg?label=circle%20ci" alt="CircleCI Status" /></a>
 <a href="https://github.com/jarun/bcal/actions"><img src="https://github.com/jarun/bcal/workflows/ci/badge.svg?branch=master" alt="GitHub CI Status" /></a>
 <a href="https://scan.coverity.com/projects/jarun-bcal"><img src="https://img.shields.io/coverity/scan/17148.svg" alt="Coverity Scan Build Status" /></a>

src/bcal.c

@@ -312,7 +312,7 @@ static int try_bc(char *expr)
 
 	buffer[ret] = '\0';
 
-	if (buffer[0] != '(') {
+	if ((buffer[0] != '(') && (strncmp(buffer, "Warning", 7) != 0) && (strncmp(buffer, "Missing", 7) != 0)) {
 		ptr = buffer;
 		while (isspace(*ptr)) /* calc results have space before them */
 			++ptr;