Replace command substitution by pipe operator to hopefully make the s…

…cript fail if the source files do not exist

restore_pkgs.sh

@@ -23,34 +23,28 @@ test -d ${cache_restore_root} || mkdir ${cache_restore_root}
 # Cache and execute post install scripts on restore.
 execute_install_scripts="${3}"
 
-cache_filepaths="$(ls -1 "${cache_dir}" | sort)"
-log "Found $(echo ${cache_filepaths} | wc -w) files in the cache."
-for cache_filepath in ${cache_filepaths}; do
+ls -1 "${cache_dir}" | sort | while read cache_filepath; do
   log "- "$(basename ${cache_filepath})""
 done
 
 log_empty_line
 
 log "Reading from main requested packages manifest..."
-for logline in $(cat "${cache_dir}/manifest_main.log" | tr ',' '\n' ); do
+cat "${cache_dir}/manifest_main.log" | tr ',' '\n' | while read logline; do
   log "- $(echo "${logline}" | tr ':' ' ')"
 done
 log "done"
 
 log_empty_line
 
 # Only search for archived results. Manifest and cache key also live here.
-cached_filepaths=$(ls -1 "${cache_dir}"/*.tar | sort)
-cached_filecount=$(echo ${cached_filepaths} | wc -w)
-
-log "Restoring ${cached_filecount} packages from cache..."
-for cached_filepath in ${cached_filepaths}; do
+ls -1 "${cache_dir}"/*.tar | sort | while read cached_filepath; do
 
   log "- $(basename "${cached_filepath}") restoring..."
   sudo tar -xf "${cached_filepath}" -C "${cache_restore_root}" > /dev/null
   log "  done"
 
-  # Execute install scripts if available.    
+  # Execute install scripts if available.
   if test ${execute_install_scripts} == "true"; then
     # May have to add more handling for extracting pre-install script before extracting all files.
     # Keeping it simple for now.