diff --git a/blddeps b/blddeps
index 652abad..df0e2c5 100755
--- a/blddeps
+++ b/blddeps
@@ -2,6 +2,21 @@
 
 . "$(dirname $0)"/libcomain
 
+usage()
+{
+    local r=$1
+    shift
+
+    cat <<EOF
+usage: $0 ACTION
+
+      build [-n]                    Build dependencies in deps/
+
+      help                          Show this help screen and exit
+EOF
+    exit $r
+}
+
 getdep()
 {
     local dep=$2
@@ -25,18 +40,44 @@ getdep()
     done
 }
 
+mbrun()
+{
+    if test $dryrun -eq 0; then
+        run "$@"
+    else
+        echo "dry-run: $@"
+    fi
+}
+
 loadoptions
 loaddeps
 
-foreach deps $nb_deps getdep | tac | while read -r name library arg; do
-    if test -e "deps/$name/$library.a" || test -e "deps/$name/$library.so"; then
-        echo $name already built.
-        continue
-    fi
-    echo Building $name
-    cd deps/$name
-    ./configure $arg && make
-    cd ../..
+if test $# -eq 0; then usage 0; fi
+
+dryrun=0
+build=0
+for arg ; do
+    case "$arg" in
+        build) build=1 ;;
+
+        -n|--dry-run) dryrun=1 ;;
+        -h|--help|help) usage 0  ;;
+        *) dief 1 "unknown action '$arg'" ;;
+    esac
 done
 
+if test $build -eq 1; then
+    foreach deps $nb_deps getdep | tac | while read -r name library arg; do
+        if test -e "deps/$name/$library.a" || test -e "deps/$name/$library.so"; then
+            echo :: $name already built.
+            continue
+        fi
+        echo :: Building $name
+        mbrun cd deps/$name
+        mbrun ./configure $arg
+        if test $? -eq 0; then mbrun make; fi
+        mbrun cd ../..
+    done
+fi
+
 echo "done."