Port bd() to POSIX sh

1 files changed, 67 insertions, 0 deletions

diff --git a/sh/shrc.d/bd.sh b/sh/shrc.d/bd.sh
new file mode 100644
index 00000000..0d1abbcf
--- /dev/null
+++ b/sh/shrc.d/bd.sh
@@ -0,0 +1,67 @@
+# Move back up the directory tree to the first directory matching the name
+bd() {
+
+    # Set positional parameters to an option terminator and what will hopefully
+    # end up being a target directory
+    set -- -- "$(
+
+        # If the first of the existing positional arguments is --, shift it
+        # off
+        [ "$1" = -- ] && shift
+
+        # There's no more than one argument after that
+        [ "$#" -le 1 ] || exit 1
+
+        # The requested pattern is the first argument, defaulting to just the
+        # parent directory
+        req=${1:-..}
+
+        # Strip trailing slashes if a trailing slash isn't the whole pattern
+        [ "$req" = / ] || req=${req%/}
+
+        # What to do now depends on the request
+        case $req in
+
+            # Just go straight to the root or dot directories if asked
+            /|.|..)
+                dirname=$req
+                ;;
+
+            # Anything with a leading / needs to anchor to the start of the
+            # path. A strange request though. Why not just use cd?
+            /*)
+                dirname=$req
+                case $PWD in
+                    "$dirname"/*) ;;
+                    *) dirname='' ;;
+                esac
+                ;;
+
+            # In all other cases, iterate through the PWD to find a match, or
+            # whittle the target down to an empty string trying
+            *)
+                dirname=$PWD
+                while [ -n "$dirname" ] ; do
+                    dirname=${dirname%/*}
+                    case $dirname in
+                        */"$req") break ;;
+                    esac
+                done
+                ;;
+        esac
+
+        # Check we have a target after all that
+        if [ -z "$dirname" ] ; then
+            printf >&2 'bd(): Directory name not in path\n'
+            exit 1
+        fi
+
+        # Print the target
+        printf '%s\n' "$dirname"
+
+    # If the subshell failed, return from the function with the same exit value
+    )" || return
+
+    # Try to change into the determined directory
+    command cd "$@"
+}