Port ud() to POSIX sh

1 files changed, 42 insertions, 0 deletions

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' "$dirname"
+
+    # If the subshell failed, return from the function with the same exit
+    # value
+    )" || return
+
+    # Try to change into the determined directory
+    command cd -- "$@"
+}