check for existance of the file(1) utility;

might not be found in lean chroots

libisoburn/trunk/releng/auto_isocontent

@@ -81,10 +81,17 @@ ln "$on_disk"/file_2 "$on_disk"/file_2_link_a || exit 1
 # trivial ISO 9660 image validation routine
 is_valid_iso9660() {
  ISOfile="$1"
+ if ! which file >/dev/null 2>&1; then
+   printf "\nFAIL : ${SELF}: Not found: file. Please install the file(1) utility.\n"
+   failure=1
+   return
+ fi
  if [ ! -f ${ISOfile} ]; then
    failure=1
    printf "\nFAIL : ${SELF} : Not found: ${ISOfile}\n"
+   return
  fi
+
  file ${ISOfile}
  if file ${ISOfile} | grep  "ISO *9660" >/dev/null 2>&1; then
    printf "\n${SELF}: Resulting ${ISOfile} OK. Looks like ISO 9660 filesystem.\n"