SPICE reader: quoted include paths don't get expanded

[fsitok]

Using KLayout as a spice parser for lctime we noticed some difficulties with include paths starting with "~".

This example with two minimal SPICE files demonstrates the problem:

top.sp:

.include "~/include.sp"

$HOME/include.sp: (empty file)

Minimal code for triggering the problem:

import klayout.db as db

n = db.Netlist()
n.read("top.sp", db.NetlistSpiceReader())

Yields:

Traceback (most recent call last):
  File "/home/user/lctime_issue4/lctime_issue4.py", line 4, in <module>
    n.read("top.sp", db.NetlistSpiceReader())
RuntimeError: Unable to open file: ./~/include.sp (errno=2) in top.sp, line 2 in Netlist.read

However, ngspice seems to be able to handle such include paths.
ngspice top.sp runs without error.

It looks like include paths in quotes are not expanded (the ~ should expand to the home directory) but instead treated as relative paths.

[klayoutmatthias]

Thanks a lot for this nicely prepared report.

There is no tilde expansion in the SPICE reader. That is done by the Linux shell (e.g. try echo ~/include.sp) and the shell is not involved here. Every path that is not absolute (i.e. starting with "/" on Linux) is treated as a relative one, which is the reason for this behavior.

Tilde expansion is not done by application code in general. For example, if you try to open such a file in Python, it will fail:

# this fails:
$ python3 -c "f = open('~/.klayout/klayoutrc')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory: '~/.klayout/klayoutrc'

# while this works:
$ python3 -c "f = open('/home/matthias/.klayout/klayoutrc')"

So I wonder why you're using tilde paths.

Matthias

[fsitok]

People started using tilde paths because ngspice does expand ~ to the home directory. Apparently ngspice does that not only in the interactive shell but also for .include statements in SPICE files. This leads to an incompatibility when using the same SPICE circuits with the SPICE reader of KLayout.

I did not find out if that is general SPICE behavior or specific to ngspice.

Indeed, not using ~ in include paths might be a way to go.

Is there a way to intercept .include statements with NetlistSpiceReaderDelegate?

[klayoutmatthias]

The implementation is very generic now and applies to add file paths in KLayout.

[klayoutmatthias]

To answer the other question: the NetlistSpiceReaderDelegate acts on a different level. It is not concerned with the file structure. So .include is not handled by the delegate.