Reorganize code and remove hack for empty block outputs

src/block.c

@@ -0,0 +1,70 @@
+#include "block.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "util.h"
+
+static int execLock = 0;
+
+void execBlock(const Block *block, const char *button) {
+    unsigned short i = block - blocks;
+
+    // Ensure only one child process exists per block at an instance
+    if (execLock & 1 << i) return;
+    // Lock execution of block until current instance finishes execution
+    execLock |= 1 << i;
+
+    if (fork() == 0) {
+        close(block->pipe[0]);
+        dup2(block->pipe[1], STDOUT_FILENO);
+        close(block->pipe[1]);
+
+        if (button) setenv("BLOCK_BUTTON", button, 1);
+
+        FILE *file = popen(block->command, "r");
+        if (!file) {
+            printf("\n");
+            exit(EXIT_FAILURE);
+        }
+
+        // Buffer will hold both '\n' and '\0'
+        char buffer[LEN(block->output) + 1];
+        if (fgets(buffer, LEN(buffer), file) == NULL) {
+            // Send an empty line in case of no output
+            printf("\n");
+            exit(EXIT_SUCCESS);
+        }
+        pclose(file);
+
+        // Trim to the max possible UTF-8 capacity
+        trimUTF8(buffer, LEN(buffer));
+
+        printf("%s\n", buffer);
+        exit(EXIT_SUCCESS);
+    }
+}
+
+void execBlocks(unsigned int time) {
+    for (int i = 0; i < blockCount; i++) {
+        const Block *block = blocks + i;
+        if (time == 0 ||
+            (block->interval != 0 && time % block->interval == 0)) {
+            execBlock(block, NULL);
+        }
+    }
+}
+
+void updateBlock(Block *block) {
+    char buffer[LEN(block->output)];
+    int bytesRead = read(block->pipe[0], buffer, LEN(buffer));
+
+    // String from pipe will always end with '\n'
+    buffer[bytesRead - 1] = '\0';
+
+    strcpy(block->output, buffer);
+
+    // Remove execution lock for the current block
+    execLock &= ~(1 << (block - blocks));
+}