Port sd() to POSIX sh

1 files changed, 82 insertions, 0 deletions

diff --git a/sh/shrc.d/sd.sh b/sh/shrc.d/sd.sh
new file mode 100644
index 00000000..c6513aac
--- /dev/null
+++ b/sh/shrc.d/sd.sh
@@ -0,0 +1,82 @@
+#
+# sd -- sibling/switch directory -- Shortcut to switch to another directory
+# with the same parent, i.e. a sibling of the current directory.
+#
+#     $ pwd
+#     /home/you
+#     $ sd friend
+#     $ pwd
+#     /home/friend
+#     $ sd you
+#     $ pwd
+#     /home/you
+#
+# If no arguments are given and there's only one other sibling, switch to that;
+# nice way to quickly toggle between two siblings.
+#
+#     $ cd -- "$(mktemp -d)"
+#     $ pwd
+#     /tmp/tmp.ZSunna5Eup
+#     $ mkdir a b
+#     $ ls
+#     a b
+#     $ cd a
+#     pwd
+#     /tmp/tmp.ZSunna5Eup/a
+#     $ sd
+#     $ pwd
+#     /tmp/tmp.ZSunna5Eup/b
+#     $ sd
+#     $ pwd
+#     /tmp/tmp.ZSunna5Eup/a
+#
+# Seems to work for symbolic links.
+#
+sd() {
+
+    set -- "$(
+    
+        # Check argument count
+        if [ "$#" -gt 1 ] ; then
+            printf >&2 'sd(): Too many arguments\n'
+            exit 1
+        fi
+
+        # Set the positional parameters to either the requested directory, or
+        # all of the current directory's siblings if no request
+        spec=$1
+        set --
+        if [ -n "$spec" ] ; then
+            set -- "$@" ../"$spec"
+        else
+            for sib in ../.* ../* ; do
+                case ${sib#../} in
+                    .|..|"${PWD##*/}") continue ;;
+                esac
+                set -- "$@" "$sib"
+            done
+        fi
+
+        # We should have exactly one sibling
+        case $# in
+            1) ;;
+            0)
+                printf >&2 'sd(): No siblings\n'
+                exit 1
+                ;;
+            *)
+                printf >&2 'sd(): More than one sibling\n'
+                exit 1
+                ;;
+        esac
+
+        # Print the target
+        printf '%s\n' "$1"
+    )"
+
+    # If the subshell printed nothing, return with failure
+    [ -n "$1" ] || return
+
+    # Try to change into the determined directory
+    command cd -- "$@"
+}