deref: init

1 files changed, 89 insertions, 0 deletions

diff --git a/pkgs/shell/deref b/pkgs/shell/deref
new file mode 100755
index 0000000..05da4ba
--- /dev/null
+++ b/pkgs/shell/deref
@@ -0,0 +1,89 @@
+#! /bin/sh
+#!buildShellBin prepend-path=coreutils:which
+#
+# NAME
+#       deref - dereference a name or path, showing all intermediaries
+#
+# SYNOPSIS
+#       deref [OPTION]... NAME...
+#
+# DESCRIPTION
+#       
+#
+#       --show=asis, --show=as-is
+#         When encountering relative file names, show them as-is.
+#         This is the default behavior.
+#
+#       --show=all
+#         When encountering relative file names, show them as-is
+#         and additionally show their absolute file name.
+#
+#       --show=abs, --show=absolute
+#         When encountering relative file names, show their absolute
+#         file name.
+#
+
+set -efu
+
+showname=asis
+case $1 in
+  (--show=asis|--show=as-is|--show=all|--show=abs|--show=absolute)
+    showname=${1#--show=}
+    shift
+    ;;
+  (-*)
+    echo "$0: bad argument: $1" >&2
+    exit 1
+    ;;
+esac
+
+showname() {
+  if test -L "$1" || test -e "$1"; then
+    case $1 in
+      /*)
+        ls -d --color "$1"
+        ;;
+      *)
+        case $showname in
+          asis|as-is)
+            ls -d --color "$1"
+            ;;
+          abs|absolute)
+            ls -d --color "$(realpath -sm "$1")"
+            ;;
+          all)
+            echo "$(ls -d --color "$1")=$(ls -d --color "$(realpath -sm "$1")")"
+            ;;
+        esac
+      ;;
+    esac
+  else
+    printf '%s' "$name"
+  fi
+}
+
+pwd=$PWD
+for name; do
+  cd "$pwd"
+  path=
+  sep=
+
+  if ! test -L "$name" && ! test -e "$name"; then
+    if which=$(which "$name" 2>/dev/null); then
+      path=$name
+      sep=' ⇒ '
+      name=$which
+    fi
+  fi
+
+  while test -L "$name"; do
+    cd "$(dirname "$name")"
+    path=${path+$path$sep}$(showname "$name")
+    sep=' → '
+    name=$(readlink "$name")
+  done
+
+  path=${path+$path$sep}$(showname "$name")
+
+  echo "$path"
+done