diff --git a/guilt b/guilt
index ec4fb04..fbc8478 100755
--- a/guilt
+++ b/guilt
@@ -167,7 +167,7 @@ verify_branch()
 
 get_top()
 {
-	tail -1 "$GUILT_DIR/$branch/status"
+	tail -n 1 "$GUILT_DIR/$branch/status"
 }
 
 get_prev()
@@ -479,10 +479,13 @@ pop_many_patches()
 		cd_to_toplevel
 
 		# remove the patches refs
-		tail -$2 < "$applied" | remove_patch_refs
+		tail -n $2 < "$applied" | remove_patch_refs
 
 		git reset --hard "$1" > /dev/null
-		head -n "-$2" < "$applied" > "$applied.tmp"
+
+		n=`wc -l < "$applied"`
+		n=`expr $n - $2`
+		head -n "$n" < "$applied" > "$applied.tmp"
 		mv "$applied.tmp" "$applied"
 	)
 }
@@ -491,7 +494,7 @@ pop_many_patches()
 pop_all_patches()
 {
 	pop_many_patches \
-		`git rev-parse refs/patches/$branch/$(head -1 "$applied")^` \
+		`git rev-parse refs/patches/$branch/$(head -n 1 "$applied")^` \
 		`wc -l < "$applied"`
 }
 
@@ -536,7 +539,7 @@ commit()
 		fi
 
 		ct=`git log -1 --pretty=%ct`
-		if [ $ct -gt `stat -c %Y "$p"` ]; then
+		if [ $ct -gt `last_modified "$p"` ]; then
 			ct=`expr $ct + 60`
 			if [ $ct -gt `date +%s` ]; then
 				touch "$p"
@@ -545,12 +548,7 @@ commit()
 			fi
 		fi
 
-		# must strip nano-second part otherwise git gets very
-		# confused, and makes up strange timestamps from the past
-		# (chances are it decides to interpret it as a unix
-		# timestamp).
-		export GIT_AUTHOR_DATE="`stat -c %y "$p" | sed -e '
-s/^\([0-9]\{4\}\)-\([0-9]\{2\}\)-\([0-9]\{2\}\) \([0-9]\{2\}\):\([0-9]\{2\}\):\([0-9]\{2\}\)\.[0-9]* \(.*\)$/\1-\2-\3 \4:\5:\6 \7/'`"
+		export GIT_AUTHOR_DATE="`format_last_modified "$p"`"
 		export GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"
 
 		# commit
@@ -717,9 +715,11 @@ __refresh_patch()
 		N=`expr "$3" - 1`
 
 		# remove the patches refs
-		tail -$N < "$applied" | remove_patch_refs
+		tail -n $N < "$applied" | remove_patch_refs
 
-		head -n "-$N" < "$applied" > "$applied.tmp"
+		n=`wc -l < "$applied"`
+		n=`expr $n - $N`
+		head -n "$n" < "$applied" > "$applied.tmp"
 		mv "$applied.tmp" "$applied"
 	)
 }
@@ -779,6 +779,50 @@ guilt_hook()
 	return $?
 }
 
+# usage: last_modified <file>
+last_modified()
+{
+	case $UNAME_S in
+		Darwin) stat -f "%a" "$1" ;;
+		Linux) stat -c "%Y" "$1" ;;
+		*) echo "Unsupported operating system: $UNAME_S" ;;
+	esac
+}
+
+# usage: last_modified <file>
+format_last_modified()
+{
+    case $UNAME_S in
+        Darwin) stat -f "%Sa" -t "%Y-%m-%d %H:%M:%S %z" "$1" ;;
+        Linux)
+		    # must strip nano-second part otherwise git gets very
+		    # confused, and makes up strange timestamps from the past
+		    # (chances are it decides to interpret it as a unix
+		    # timestamp).
+            stat -c "%y" "$1" | sed -e '
+s/^\([0-9]\{4\}\)-\([0-9]\{2\}\)-\([0-9]\{2\}\) \([0-9]\{2\}\):\([0-9]\{2\}\):\([0-9]\{2\}\)\.[0-9]* \(.*\)$/\1-\2-\3 \4:\5:\6 \7/';;
+        *) echo "Unsupported operating system: $UNAME_S" ;;
+    esac
+}
+
+# usage: head -n [count]
+head() {
+	case $UNAME_S in
+		Darwin) if [ "$2" -gt 0 ]; then "$HEAD" -n "$2"; fi ;;
+		Linux) "$HEAD" -n "$2" ;;
+		*) echo "Unsupported operating system: $UNAME_S" ;;
+	esac
+}
+
+# usage: sha1 [file]
+sha1() {
+	case $UNAME_S in
+		Darwin) openssl dgst -sha1 "$1" ;;
+		Linux) sha1sum "$1" ;;
+		*) echo "Unsupported operating system: $UNAME_S" ;;
+	esac
+}
+
 #
 # Some constants
 #
@@ -829,3 +873,6 @@ guards_file="$GUILT_DIR/$branch/guards"
 # determine a pager to use for anything interactive (fall back to more)
 pager="more"
 [ ! -z "$PAGER" ] && pager="$PAGER"
+
+UNAME_S=`uname -s`
+HEAD=`which head`
diff --git a/guilt-branch b/guilt-branch
index 125bb1a..f81adb2 100755
--- a/guilt-branch
+++ b/guilt-branch
@@ -36,7 +36,13 @@ git checkout "$newbranch"
 mkdir -p "$GUILT_DIR/`dirname $newbranch`"
 
 # copy the patch dir
-cp -a "$GUILT_DIR/$branch" "$GUILT_DIR/$newbranch"
+case $UNAME_S in
+	# Darwin doesn't have the GNU equalient -d (--no-dereference --preserve=links),
+	# flags
+	Darwin) cp -p "$GUILT_DIR/$branch" "$GUILT_DIR/$newbranch" ;;
+	Linux) cp -a "$GUILT_DIR/$branch" "$GUILT_DIR/$newbranch" ;;
+	*) echo "Unsupported operating system: $UNAME_S" ;;
+esac
 
 # copy the refs
 
diff --git a/guilt-files b/guilt-files
index ee129b9..e90a8e9 100755
--- a/guilt-files
+++ b/guilt-files
@@ -31,7 +31,7 @@ IFS=:
 if [ -n "$opt_all" ]; then
 	cat $applied
 else
-	tail -1 $applied
+	tail -n 1 $applied
 fi | while read patch; do
 	obj=`git rev-parse refs/patches/$branch/$patch`
 
diff --git a/guilt-graph b/guilt-graph
index 0fb4e79..9514186 100755
--- a/guilt-graph
+++ b/guilt-graph
@@ -12,7 +12,7 @@ fi
 
 patchname="$1"
 
-bottom=`git rev-parse refs/patches/$branch/$(head -1 < "$applied")`
+bottom=`git rev-parse refs/patches/$branch/$(head -n 1 < "$applied")`
 base=`git rev-parse $bottom^`
 
 if [ -z "$patchname" ]; then
@@ -55,7 +55,7 @@ while [ "$current" != "$base" ]; do
 
 	getfiles $current | while read f; do
 		# hash the filename
-		fh=`echo "$f" | sha1sum | cut -d' ' -f1`
+		fh=`echo "$f" | sha1 | cut -d' ' -f1`
 		if [ -e "$cache/$fh" ]; then
 			# ok, something already touched this file before us
 			cat "$cache/$fh" >> "$cache/dep"
diff --git a/guilt-push b/guilt-push
index 1fae40b..8c16628 100755
--- a/guilt-push
+++ b/guilt-push
@@ -102,7 +102,7 @@ if [ "$sidx" -gt "$eidx" ]; then
 	if [ "$sidx" -le "`get_series | wc -l`" ]; then
 		disp "Patch is already applied."
 	else
-		disp "File series fully applied, ends at patch `get_series | tail -1`"
+		disp "File series fully applied, ends at patch `get_series | tail -n 1`"
 	fi
 	exit 0
 fi
diff --git a/guilt-rebase b/guilt-rebase
index ebfe056..4da1a25 100755
--- a/guilt-rebase
+++ b/guilt-rebase
@@ -80,7 +80,7 @@ cat "$rebase_dir/status" | while read hash name; do
 		while read patchid commitid ; do
 			disp "Applying '$name'"
 			if [ -f "$rebase_dir/$patchid" ]; then
-				realcommit=`head -1 "$rebase_dir/$patchid"`
+				realcommit=`head -n 1 "$rebase_dir/$patchid"`
 				disp "Matches upstream commit $realcommit"
 				series_rename_patch "$name" "###rebased###$name"
 				disp "Patch removed from series."
diff --git a/guilt-repair b/guilt-repair
index 163ac18..17a25bc 100755
--- a/guilt-repair
+++ b/guilt-repair
@@ -82,7 +82,7 @@ repair_pushed()
 {
 	if [ -s "$applied" ]; then
 		# there were some patches applied
-		newrev=`git rev-parse refs/patches/$branch/$(head -1 < "$applied")^`
+		newrev=`git rev-parse refs/patches/$branch/$(head -n 1 < "$applied")^`
 	else
 		# no patches were applied, but let's do all the work anyway
 		newrev="$oldrev"
diff --git a/guilt-series b/guilt-series
index 031ff04..e233391 100755
--- a/guilt-series
+++ b/guilt-series
@@ -25,8 +25,8 @@ if [ ! -z "$edit" ]; then
 	git_editor "$series"
 elif [ ! -z "$gui" ]; then
 	[ -z "`get_top`" ] && die "No patches applied."
-	bottom=`git rev-parse refs/patches/$branch/$(head -1 $applied)`
-	top=`git rev-parse refs/patches/$branch/$(tail -1 $applied)`
+	bottom=`git rev-parse refs/patches/$branch/$(head -n 1 $applied)`
+	top=`git rev-parse refs/patches/$branch/$(tail -n 1 $applied)`
 	range="$bottom..$top"
 
 	# FIXME, this doesn't quite work - it's perfectly fine with