From 40b620f61bc26e59c20adc74500062a558c4999e Mon Sep 17 00:00:00 2001
From: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Date: Thu, 28 Apr 2022 19:26:18 -0400
Subject: add POSIX same_file fallback, absolute file check

---
 nextbin | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/nextbin b/nextbin
index 006b158..d688fa9 100755
--- a/nextbin
+++ b/nextbin
@@ -23,9 +23,35 @@ die() {
     exit 1
 }
 
-[ / -ef / ] || exec bash "$0" "$orig_exe" "$@" || die "test -ef doesn't work, and bash not found"
 [ -n "$PATH" ] || die 'PATH is empty'
 
+# shellcheck disable=SC3013
+if [ / -ef / ] && ! [ / -ef /dev/null ]; then
+    same_file() {
+        # shellcheck disable=SC3013
+        [ "$1" -ef "$2" ]
+    }
+else
+    if command -v bash >/dev/null 2>&1; then
+        exec bash "$0" "$orig_exe" "$@"
+    fi
+    ino() {
+        ls=$(ls -i "$1")
+        printf '%s\n' "${ls%% *}"
+    }
+    dev() {
+        df -P "$1" | awk 'END{print $1}'
+    }
+    same_file() {
+        [ "$(ino "$1")" = "$(ino "$2")" ] && [ "$(dev "$1")" = "$(dev "$2")" ]
+    }
+fi
+
+case $orig_exe in
+    /*) ;;
+    *) die 'non-absolute $0'
+esac
+
 exe_name=${orig_exe##*/}
 path=$PATH
 phase=1
@@ -34,10 +60,10 @@ while :; do
     exe=${path%%:*}/$exe_name
     if [ -f "$exe" ] && [ -x "$exe" ]; then
         if [ "$phase" = 1 ]; then
-            if [ "$exe" -ef "$orig_exe" ]; then
+            if same_file "$exe" "$orig_exe"; then
                 phase=2
             fi
-        elif [ "$exe" -ef "$orig_exe" ]; then
+        elif same_file "$exe" "$orig_exe"; then
             [ -z "$found" ] || die 'duplicate PATH entries found'
         elif [ -z "$found" ]; then
             found=$exe
-- 
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