n2o · March 26, 2025 15:24 · Mar 26, 2025
diff --git a/sha256.md b/sha256.md
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+# SHA256-Function in VBA for Mac-Users and Microsoft Excel
+
+I needed a function to hash a cell's content in Microsoft Excel. Internal calls to .NET functions don't work on a Mac. Also the Python-Integration is only available in Business-Plans. So I wrote a VBA function to hash a string with SHA256 on a Mac.
+
+This VBA function uses the Mac's internal `sha256` implementation, makes a system call and returns the hash. The function is called `SHA256_Mac` and takes a string as input. The function returns the hash as a string.
+
+Add it to your macro-enabled Excel file and use it like this:
+
+```excel
+=SHA256_Mac("abc")
+
+=> BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD
+```
+
+Or reference a cell:
+
+```excel
+=SHA256_Mac(A1)
+```
+
+---
+
+```vba
+Function SHA256_Mac(text As String) As String
+    Dim script As String
+    Dim result As String
+
+    'Escape special characters
+    Dim safeText As String
+    safeText = Replace(text, "'", "'\''")
+    safeText = Replace(safeText, """", "\""")
+
+    'Explicit UTF-8 encoding
+    script = "do shell script ""export LANG=en_US.UTF-8; printf '%s' '" & safeText & "' | shasum -a 256 | cut -d ' ' -f 1"""
+
+    On Error Resume Next
+    result = MacScript(script)
+    On Error GoTo 0
+
+    'Clean result
+    result = Trim(result)
+    If Len(result) = 64 Then
+        SHA256_Mac = UCase(result)
+    Else
+        SHA256_Mac = "ERROR: " & result
+    End If
+End Function
+```