Port ud() to POSIX sh

3 files changed, 43 insertions, 51 deletions

diff --git a/README.markdown b/README.markdown
index 3bf1e604..6e6f2bbb 100644
--- a/README.markdown
+++ b/README.markdown
@@ -187,6 +187,7 @@ in `sh/shrc.d` to be loaded by any POSIX interactive shell. Those include:
     preserved; I hate ending up `root`-owned files in my home directory.
 *   `tmux()` changes the default command for `tmux(1)` to `attach-session -d`
     if a session exists, or creates a new session if one doesn't.
+*   `ud()` changes into an indexed ancestor of a directory.
 *   `vim()` defines three functions to always use `vim(1)` as my `ex(1)`,
     `vi(1)` and `view(1)` implementation if it's available.
 
@@ -211,7 +212,6 @@ There are a few other little tricks defined for other shells, mostly in
 *   `readv()` prints names and values from `read` calls to `stderr`.
 *   `readz()` is an alias for `read -d '' -r`.
 *   `sd()` changes into a sibling of the current directory.
-*   `ud()` changes into an indexed ancestor of a directory.
 *   `vared()` allows interactively editing a variable with Readline, emulating
     a Zsh function I like by the same name.
 *   `vr()` tries to change to the root directory of a source control
diff --git a/bash/bashrc.d/ud.bash b/bash/bashrc.d/ud.bash
deleted file mode 100644
index e23de1fa..00000000
--- a/bash/bashrc.d/ud.bash
+++ /dev/null
@@ -1,50 +0,0 @@
-# Shortcut to step up the directory tree with an arbitrary number of steps,
-# like cd .., cd ../.., etc
-ud() {
-
-    # 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[@]}]=$arg
-                ;;
-            *)
-                break
-                ;;
-        esac
-    done
-
-    # Check and save optional first argument, number of steps upward; default
-    # to 1 if absent
-    local -i steps
-    steps=${1:-1}
-    if ! ((steps > 0)) ; then
-        printf 'bash: %s: Invalid step count %s\n' "$FUNCNAME" "$1" >&2
-        return 2
-    fi
-
-    # Check and save optional second argument, target directory; default to
-    # $PWD (typical usage case)
-    local dirname
-    dirname=${2:-"$PWD"}
-    if [[ ! -e $dirname ]] ; then
-        printf 'bash: %s: Target directory %s does not exist\n' "$FUNCNAME" "$2" >&2
-        return 1
-    fi
-
-    # Append /.. to the target the specified number of times
-    local -i i
-    for (( i = 0 ; i < steps ; i++ )) ; do
-        dirname=${dirname%/}/..
-    done
-
-    # Try to change into it
-    cd "${opts[@]}" -- "$dirname"
-}
diff --git a/sh/shrc.d/ud.sh b/sh/shrc.d/ud.sh
new file mode 100644
index 00000000..0dfd858c
--- /dev/null
+++ b/sh/shrc.d/ud.sh
@@ -0,0 +1,42 @@
+# Shortcut to step up the directory tree with an arbitrary number of steps,
+# like cd .., cd ../.., etc
+ud() {
+
+    # Change the positional parameters from the number of steps given to a
+    # "../../.." string
+    set -- "$(
+
+        # Check first argument, number of steps upward, default to 1
+        # "0" is weird, but valid; "-1" however makes no sense at all
+        steps=${1:-1}
+        if [ "$steps" -lt 0 ] ; then
+            printf >&2 'ud(): Invalid step count\n'
+            exit 2
+        fi
+
+        # Check second argument, target directory, default to $PWD
+        dirname=${2:-"$PWD"}
+
+        # Append /.. to the target the specified number of times
+        i=0
+        while [ "$i" -lt "$steps" ] ; do
+            dirname=${dirname%/}/..
+            i=$((i+1))
+        done
+
+        # Check we have a target after all that
+        if [ -z "$dirname" ] ; then
+            printf >&2 'ud(): Destination construction failed\n'
+            exit 1
+        fi
+
+        # Print the target
+        printf '%s\n' "$dirname"
+
+    # If the subshell failed, return from the function with the same exit
+    # value
+    )" || return
+
+    # Try to change into the determined directory
+    command cd -- "$@"
+}