Issue 6577: remove confirmation to delete output directory

build_image

 #!/bin/bash
 
 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to build a bootable keyfob-based chromeos system image from within
 # a chromiumos setup. This assumes that all needed packages have been built into
 # the given target's root with binary packages turned on. This script will
 # build the Chrome OS image using only pre-built binary packages.
@@ skipping 301 matching lines @@
     ESP_LOOP_DEV=
   fi
 
   # Turn die on error back on.
   set -e
 }
 
 delete_prompt() {
   echo "An error occurred in your build so your latest output directory" \
     "is invalid."
-  read -p "Would you like to delete the output directory (y/N)? " SURE
-  SURE="${SURE:0:1}" # Get just the first character.
+
+  # Only prompt if both stdin and stdout are a tty. If either is not a tty,
+  # then the user may not be present, so we shouldn't bother prompting.
+  if tty -s && tty -s <&1; then
+    read -p "Would you like to delete the output directory (y/N)? " SURE
+    SURE="${SURE:0:1}" # Get just the first character.
+  else
+    SURE="y"
+    echo "Running in non-interactive mode so deleting output directory."
+  fi
   if [ "${SURE}" == "y" ] ; then
     sudo rm -rf "${OUTPUT_DIR}"
     echo "Deleted ${OUTPUT_DIR}"
   else
-    echo "Not deleting ${OUTPUT_DIR}. Note dev server updates will not work" \
-      "until you successfully build another image or delete this directory"
+    echo "Not deleting ${OUTPUT_DIR}."
   fi
 }
 
 # $1 - Directory where developer rootfs is mounted.
 # $2 - Directory where developer stateful_partition is mounted.
 # $3 - Directory where the ESP partition is mounted.
 mount_gpt_cleanup() {
   local rootfs="${1-$ROOT_FS_DIR}"
   local statefs="${2-$STATEFUL_FS_DIR}"
   local espfs="${3-$ESP_FS_DIR}"
@@ skipping 410 matching lines @@
   echo "Developer image created as ${DEVELOPER_IMAGE_NAME}"
 fi
 
 print_time_elapsed
 
 echo "To copy to USB keyfob, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_usb.sh --from=${OUTSIDE_OUTPUT_DIR} --to=/dev/sdX"
 echo "To convert to VMWare image, INSIDE the chroot, do something like:"
 echo "  ./image_to_vm.sh --from=${OUTSIDE_OUTPUT_DIR} --board=${BOARD}"
 echo "from the scripts directory where you entered the chroot."