Implement a wrapper for sed to try to have a consistent syntax

for regular expressions across platforms. This is an attempt to try
to fix #33 .

unrarall

@@ -20,6 +20,7 @@
 
 # Set some defaults
 declare -x FIND="find" #set to gfind to use homebrew's GNU findutils on OSX Yosemite
+declare -x SED="sed"
 declare -x DIR=""
 declare -x RM="rm"
 declare -rx UNRARALL_VERSION="0.4.3"
@@ -234,7 +235,7 @@ function detect_clean_up_hooks()
         continue
     fi
 
-    UNRARALL_DETECTED_CLEAN_UP_HOOKS[$index]=$( echo "$hook" | sed 's/unrarall_clean_//')
+    UNRARALL_DETECTED_CLEAN_UP_HOOKS[$index]=$( echo "$hook" | sed_wrapper 's/unrarall_clean_//')
     ((index++))
   done
 
@@ -247,8 +248,11 @@ function detect_clean_up_hooks()
 #This is posix egrep style regex
 function find_regex_escape()
 {
-  #echo "$1" | sed 's#\\#\\\\#g ;s/\?/\\?/g ; s/\./\\./g ; s/\+/\\+/g ; s/\*/\\*/g; s/\^/\\^/g ; s/\$/\\$/g; s/\[/\\[/g; s/\]/\\]/g;'
-  echo "$1" | sed 's#\\#\\\\#g ;s/\?/\\?/g ; s/\./\\./g ; s/\+/\\+/g ; s/\*/\\*/g; s/\^/\\^/g ; s/\$/\\$/g; s/\[/\\[/g; s/\]/\\]/g; s/(/\\(/g; s/)/\\)/g; s/|/\\|/g;'
+  echo "$1" | sed_wrapper 's#\\#\\\\#g ;s/\?/\\?/g ; s/\./\\./g ; s/\+/\\+/g ; s/\*/\\*/g; s/\^/\\^/g ; s/\$/\\$/g; s/\[/\\[/g; s/\]/\\]/g; s/\(/\\(/g; s/\)/\\)/g; s/\|/\\|/g;'
+  if [ $? -ne 0 ]; then
+    message error "Failed to escape"
+    exit 1
+  fi
 }
 
 #Helper function for hooks to remove a single file/folder
@@ -430,6 +434,23 @@ function unrarall_clean_empty_folders()
 
 #end of clean-up hooks
 
+# Detect the version of sed available and create a wrapper function
+# that will behave like sed using "extended regular expressions"
+# This is to force consistency across multiple platforms.
+if [ "X$(${SED} --version >/dev/null 2>&1 ; echo $?)" == "X0" ]; then
+  # GNU find supports `--version`
+  [ $VERBOSE -eq 1 ] && message info "Detected GNU sed"
+  function sed_wrapper() {
+    ${SED} --regexp-extended "$@"
+  }
+else
+  # Assume *BSD/macOS sed
+  [ $VERBOSE -eq 1 ] && message info "Detected BSD sed"
+  function sed_wrapper() {
+    ${SED} -E "$@"
+  }
+fi
+
 
 # Parse command line arguments
 if [ "$#" -lt 1 ]; then
@@ -458,7 +479,7 @@ while [ -n "$1" ]; do
       ;;
       --clean=*)
         index=0;
-        for hook in $( echo "$1" | sed 's/--clean=//' | tr , " ") ; do
+        for hook in $( echo "$1" | sed_wrapper 's/--clean=//' | tr , " ") ; do
           UNRARALL_CLEAN_UP_HOOKS_TO_RUN[$index]="$hook"
           ((index++))
         done
@@ -515,7 +536,7 @@ while [ -n "$1" ]; do
       ;;
       --backend=*)
         # If using `--dry` don't modify UNRARALL_BIN
-        requested_backend="$( echo "$1" | sed 's/--backend=//')"
+        requested_backend="$( echo "$1" | sed_wrapper 's/--backend=//')"
         if [ "$UNRARALL_BIN" != 'echo' ]; then
           case "${requested_backend}" in
             unrar)
@@ -572,6 +593,7 @@ else
   }
 fi
 
+
 detect_clean_up_hooks
 
 #Verify selected clean-up hooks are ok
@@ -669,7 +691,7 @@ for file in $(find_wrapper "$DIR" -depth -iregex '.*\.(rar|001)$'); do
   # if rar is of style partxx.rar then only extract $filename.part01.rar
   if [[ "$file" =~ .part[0-9]+.rar$ ]]; then
     if [[ "$file" =~ .part0*1.rar$ ]]; then
-      sfilename=`echo "$sfilename" | sed 's/\.part[0-9]\+$//'`
+      sfilename=`echo "$sfilename" | sed_wrapper 's/\.part[0-9]+$//'`
       [ $VERBOSE -eq 1 ] && message info "Using rar 3.x split archive format"
     else
       continue