allow AOF to be fixed by truncating to the portion of the file that is valid

redis-check-aof.c

 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 #include <sys/stat.h>
 #include "config.h"
 
@@ -126,34 +127,58 @@ long process(FILE *fp) {
 int main(int argc, char **argv) {
     /* expect the first argument to be the dump file */
     if (argc <= 1) {
-        printf("Usage: %s <file.aof>\n", argv[0]);
+        printf("Usage: %s [--fix] <file.aof>\n", argv[0]);
         exit(0);
     }
 
-    FILE *fp = fopen(argv[1],"r");
+    char *filename;
+    int fix = 0;
+    if (argc == 3) {
+        if (strcmp(argv[1],"--fix") != 0) {
+            printf("Invalid argument: %s\n", argv[1]);
+            exit(1);
+        }
+        fix = 1;
+        filename = argv[2];
+    } else if (argc == 2) {
+        filename = argv[1];
+    } else {
+        printf("Invalid argument");
+        exit(1);
+    }
+
+    FILE *fp = fopen(filename,"r+");
     if (fp == NULL) {
-        printf("Cannot open file: %s\n", argv[1]);
+        printf("Cannot open file: %s\n", filename);
         exit(1);
     }
 
     struct redis_stat sb;
     if (redis_fstat(fileno(fp),&sb) == -1) {
-        printf("Cannot stat file: %s\n", argv[1]);
+        printf("Cannot stat file: %s\n", filename);
         exit(1);
     }
 
     long size = sb.st_size;
     if (size == 0) {
-        printf("Empty file: %s\n", argv[1]);
+        printf("Empty file: %s\n", filename);
         exit(1);
     }
 
     long pos = process(fp);
     if (pos < size) {
-        printf("First invalid operation at offset %ld.\n", pos);
-        exit(1);
+        if (fix) {
+            if (ftruncate(fileno(fp), pos) == -1) {
+                printf("Could not truncate AOF to size %ld\n", pos);
+                exit(1);
+            } else {
+                printf("AOF succesfully truncated to %ld bytes\n", pos);
+            }
+        } else {
+            printf("First invalid operation at offset %ld\n", pos);
+        }
     } else {
-        printf("AOF is valid.\n");
+        printf("AOF is valid\n");
     }
 
     fclose(fp);