From c41b93e768014e2a3d3d6376b78e790333451076 Mon Sep 17 00:00:00 2001
From: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Date: Sun, 6 Mar 2022 12:58:06 -0500
Subject: simplify algorithm

---
 nextbin | 91 +++++++++++++++--------------------------------------------------
 1 file changed, 20 insertions(+), 71 deletions(-)

(limited to 'nextbin')

diff --git a/nextbin b/nextbin
index fd8faa5..31241ef 100755
--- a/nextbin
+++ b/nextbin
@@ -23,81 +23,30 @@ orig_exe=$1
 shift
 exe_name=${orig_exe##*/}
 
-[ -n "$PATH" ] || die 'PATH is empty'
-
-case "$orig_exe" in
-    */)
-        die 'ends with /'
-        ;;
-
-    */*)
-        orig_dir=${orig_exe%/*}
-        ;;
-
-    *)
-        # either shell has not resolved script-file into a path, or script is
-        # in cwd and PATH has . or empty entries
-        if ! [ -d "$orig_exe" ] && [ -x "$orig_exe" ]; then
-            case ":$PATH:" in
-                *::*:.:*|*:.:*::*)
-                    die 'exe in cwd and PATH has both . and empty entries'
-                    ;;
+case ":$PATH:" in
+    ::) die 'empty PATH not supported' ;;
+    *:[!/]*) die 'relative PATH elements not supported' ;;
+    *:*/./*:*|*:*/../*:*) die 'PATH elements containing . or .. not supported' ;;
+esac
 
-                *::*)
-                    orig_dir=
-                    ;;
+case $orig_exe in
+    # theoretically this could be optimized but it's negligible cost
+    */*) orig_dir=$(cd -L "${orig_exe%/*}" && pwd -L) ;;
+    *) orig_dir=$PWD ;;
+esac
 
-                *:.:*)
-                    orig_dir=.
-                    ;;
+# clean up path. theoretically we could allow e.g. PATH=/dir://dir but which
+# would we match for cd /dir; ./exe
+tmp_path=$(printf '%s\n' ":$PATH:" | sed -e 's|/*:|:|g' -e 's|//|/|g')
 
-                *)
-                    die 'missing /'
-            esac
-        fi
+case $tmp_path in
+    *:$orig_dir:$orig_dir:*|*:$orig_dir:*:$orig_dir:*)
+        die 'duplicate entry in PATH: %s' "$orig_dir"
 esac
 
-tmp_path=:$PATH:
-new_path=${tmp_path#*:$orig_dir:}
-[ -n "$new_path" ] \
-    || die '%s is last PATH entry' "$orig_dir"
-if [ "$new_path" != "$tmp_path" ]; then
-    new_path_2=${new_path#*:$orig_dir:}
-    [ "$new_path" = "$new_path_2" ] \
-        || die 'duplicate entry in PATH: %s' \
-            "$orig_exe" "$orig_dir"
-else
-    # try to find equivalent path
-    found_alt_dir=
-    new_orig_dir=
-    equiv_orig_dir=$(cd "${orig_dir:-.}" && pwd -L)
-    tmp_path_2=$PATH
-    while :; do
-        p=${tmp_path_2%%:*}
-        if [ "$(cd "$p" >/dev/null 2>&1 && pwd -L)" = "$equiv_orig_dir" ]; then
-            [ -z "$found_alt_dir" ] \
-                || die "duplicate equivalent path in PATH: '%s' = '%s'" \
-                    "$new_orig_dir" "$p"
-            found_alt_dir=1
-            new_orig_dir=$p
-        fi
-        case "$tmp_path_2" in
-            *:*) tmp_path_2=${tmp_path_2#*:};;
-            *) break
-        esac
-    done
-    if [ -n "$found_alt_dir" ]; then
-        new_path=${tmp_path#*:$new_orig_dir:}
-        [ -n "$new_path" ] \
-            || die '%s is last PATH entry' "$new_orig_dir"
-    else
-        new_path=$PATH:
-    fi
-fi
-
-exe=$(PATH="${new_path%:}" command -v "$exe_name") || true
-[ -n "$exe" ] \
-    || die 'PATH lookup failed using %s' \
-        "${new_path%:}"
+new_path=${tmp_path#*":$orig_dir:"}
+new_path=${new_path%:}
+exe=$(PATH="$new_path" command -v "$exe_name") || true
+[ -n "$exe" ] || die 'PATH lookup failed using %s' "$new_path"
 
 $action "$exe" "$@"
-- 
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