xar @1.8.0.452: No longer supports extracting to stdout

[ryandesign (Ryan Carsten Schmidt)]

xar @1.6.1 supported extracting to stdout with the -O / --to-stdout flag. Last year xar was switched to version 1.8.0.452 of Apple's xar, which does not support extracting to stdout. Any solution? I want to extract to stdout.

[Schamschula (Marius Schamschula)]

Hmm. The first I've heard of this issue.

[ryandesign (Ryan Carsten Schmidt)]

Assuming I have not overlooked some stdout capability in Apple's xar, possible solutions I see:

• Add ​the stdout capability to Apple's xar.
• Revert to mackyle's xar 1.6.1. (Apple's xar is already available at /usr/bin/xar.)
• Offer two ports, one for Apple's xar and one for mackyle's xar.

[Schamschula (Marius Schamschula)]

I think I'll try to add the patch to Apple xar.

If I can't make that work, I'll add a second port.

Note: both branches are not well supported upstream. Apple has clearly noted that there is no more development, and mackyle's hasn't see any updates for years as well.

[Schamschula (Marius Schamschula)]

It looks like the patch fails 13 of 14 hunks. I don't have time right now to see if I can fix them. However, I'll get back to it soon.

[Schamschula (Marius Schamschula)]

Unfortunately, I found the following ​https://github.com/mackyle/xar/issues/15 (see comment Jun. 5, 2017, by the owner). There are open issues including with openssl.

The Apple version has support (patches) from other platforms (Gentoo).

[Schamschula (Marius Schamschula)]

In 3cc8ae1d99eab3c4b63e2c2fc14ba7b4d59b7f3e/macports-ports (master):

xar: add --to-stdout

See: #64775

[Schamschula (Marius Schamschula)]

I have no xar archives handy for testing, hence I didn't close this ticket.

[ryandesign (Ryan Carsten Schmidt)]

Thanks!

You can create archives with xar for testing, for example:

$ echo hello world > test.txt
$ xar -cf test.xar test.txt

To extract to stdout:

$ xar -xOf test.xar

With mackyle's xar @1.6.1_6 the result is:

hello world

With Apple's xar @1.8.0.452_3 the result is:

--to-stdout requires a newer xar library

Looks like the whole concept of having ​different libxar library versions with different capabilities was added by mackyle too.

Since we know the library and program are provided as a matched set by the port, we could just dispense with the library version checking. When I do that, the result of trying to extract to stdout is that the -O flag is silently ignored; the file test.txt is created in the current directory.

I think the commit I mentioned at the beginning was only the part that modified the xar command line program to be able to use the to-stdout capability of the libxar library; we still need to patch that support into the library. I'll see if I can dig it up and send you the patch.

[ryandesign (Ryan Carsten Schmidt)]

Replying to ryandesign:

the to-stdout capability of the libxar library

Looks like at least ​this commit is involved. I'll try to extract the relevant parts...

[ryandesign (Ryan Carsten Schmidt)]

​https://github.com/macports/macports-ports/pull/14230

[ryandesign (Ryan Carsten Schmidt)]

In 713c22863e4fe2624bc455f9bf6818118e53b987/macports-ports (master):

xar: Fix to-stdout functionality

Closes: #64775

[ryandesign (Ryan Carsten Schmidt)]

Great! This functionality is used in the ​MacOSX10.12.sdk port and upcoming newer SDK ports.