fix bug in utils::fgets_trunc(). closes #2878

src/utils.cpp

@@ -176,20 +176,23 @@ char *utils::fgets_trunc(char *buf, int size, FILE *fp)
   char dummy[MAXDUMMY];
   char *ptr = fgets(buf, size, fp);
 
-  // EOF
+  // EOF?
   if (!ptr) return nullptr;
 
   int n = strlen(buf);
 
-  // line is shorter than buffer, append newline if needed,
-  if (n < size - 2) {
+  // check the string being read in:
+  // - if string is shorter than the buffer make sure it has a final newline and return
+  // - if string is exactly the size of the buffer and has a final newline return
+  // - otherwise truncate with final newline and read into dummy buffer until EOF or newline is found
+  if (n < size - 1) {
     if (buf[n - 1] != '\n') {
       buf[n] = '\n';
       buf[n + 1] = '\0';
     }
     return buf;
-
-    // line fits exactly. overwrite last but one character.
+  } else if (buf[n - 1] == '\n') {
+    return buf;
   } else
     buf[size - 2] = '\n';
 
@@ -202,7 +205,7 @@ char *utils::fgets_trunc(char *buf, int size, FILE *fp)
       n = 0;
   } while (n == MAXDUMMY - 1 && ptr[MAXDUMMY - 1] != '\n');
 
-  // return first chunk
+  // return truncated chunk
   return buf;
 }