Port bd() to POSIX sh

2 files changed, 67 insertions, 78 deletions

diff --git a/bash/bashrc.d/bd.bash b/bash/bashrc.d/bd.bash
deleted file mode 100644
index 23a2d380..00000000
--- a/bash/bashrc.d/bd.bash
+++ /dev/null
@@ -1,78 +0,0 @@
-# Move back up the directory tree to the first directory matching the name
-bd() {
-
-    # For completeness' sake, we'll pass any options to cd
-    local arg
-    local -a opts
-    for arg ; do
-        case $arg in
-            --)
-                shift
-                break
-                ;;
-            -*)
-                shift
-                opts[${#opts[@]}]=$arg
-                ;;
-            *)
-                break
-                ;;
-        esac
-    done
-
-    # We should have zero or one arguments after all that, bail if there are
-    # more
-    if (($# > 1)) ; then
-        printf 'bash: %s: usage: %s [PATH]\n' \
-            "$FUNCNAME" "$FUNCNAME" >&2
-        return 2
-    fi
-
-    # The requested pattern is the first argument; strip trailing slashes if
-    # there are any
-    local req=$1
-    [[ $req != / ]] || req=${req%/}
-
-    # What to do now depends on the request
-    local dirname
-    case $req in
-
-        # If no argument at all, just go up one level
-        '')
-            dirname=..
-            ;;
-
-        # Just go straight to the root or dot directories if asked
-        /|.|..)
-            dirname=$req
-            ;;
-
-        # Anything else with a leading / needs to anchor to the start of the
-        # path
-        /*)
-            dirname=$req
-            if [[ $PWD != "$dirname"/* ]] ; then
-                printf 'bash: %s: Directory name not in path\n' \
-                    "$FUNCNAME" >&2
-                return 1
-            fi
-            ;;
-
-        # In all other cases, iterate through the directory tree to find a
-        # match, or whittle the dirname down to an empty string trying
-        *)
-            dirname=${PWD%/*}
-            while [[ -n $dirname && $dirname != */"$req" ]] ; do
-                dirname=${dirname%/*}
-            done
-            if [[ -z $dirname ]] ; then
-                printf 'bash: %s: Directory name not in path\n' \
-                    "$FUNCNAME" >&2
-                return 1
-            fi
-            ;;
-    esac
-
-    # Try to change into the determined directory
-    builtin cd "${opts[@]}" -- "$dirname"
-}
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 "$@"
+}