threads / discuss / 59121

Redirect isn't working:

Subject: Redirect isn't working:

## tl;dr

3 messages between Jan 19, 2023 and Mar 27, 2023.

replies: 2people: 3as markdown or json

Jack Adrian Zappa· Jan 19, 2023, 18:06 UTC · lore

Here is the filled out form for submitting a bug report:

What did you do before the bug happened? (Steps to reproduce your issue)

  At the command line, I typed the following command:

  $ git diff --no-index --word-diff --color=always <(od -An -t x1
-w10000000000 file1.txt) <(od -An -t x1 -w10000000000 file2.txt)

What did you expect to happen? (Expected behavior)

  I expected to see the diff of the two files.

What happened instead? (Actual behavior)

  Instead I saw this:

  error: Could not access '/proc/1961/fd/63'

What's different between what you expected and what actually happened?

  The difference is that I would get the difference between the two
files as opposed to a critical failure message.

Anything else you want to add:

  Nope.

Please review the rest of the bug report below. You can delete any lines you don't wish to share.

[System Info] git version: git version 2.38.1.windows.1 cpu: x86_64 built from commit: b85c8f604d375d4d773a36842964e8a7ec056aae sizeof-long: 4 sizeof-size_t: 8 shell-path: /bin/sh feature: fsmonitor--daemon uname: Windows 10.0 19044 compiler info: gnuc: 12.2 libc info: no libc information available $SHELL (typically, interactive shell): C:\Program Files\Git\usr\bin\bash.exe

[Enabled Hooks] not run from a git repository - no hooks to show

brian m. carlson· Jan 20, 2023, 01:46 UTC · re: Jack Adrian Zappa · lore

Re: Redirect isn't working:

On 2023-01-19 at 18:06:17, Jack Adrian Zappa wrote:

Show 23 quoted lines

> Here is the filled out form for submitting a bug report:
> 
> What did you do before the bug happened? (Steps to reproduce your issue)
> 
>   At the command line, I typed the following command:
> 
>   $ git diff --no-index --word-diff --color=always <(od -An -t x1
> -w10000000000 file1.txt) <(od -An -t x1 -w10000000000 file2.txt)
> 
> What did you expect to happen? (Expected behavior)
> 
>   I expected to see the diff of the two files.
> 
> What happened instead? (Actual behavior)
> 
>   Instead I saw this:
> 
>   error: Could not access '/proc/1961/fd/63'
> 
> What's different between what you expected and what actually happened?
> 
>   The difference is that I would get the difference between the two
> files as opposed to a critical failure message.

Thanks for the report. This has come up before (and I attempted a patch), but the ultimate problem here is that the /proc/PID/fd/* files are symlinks on Linux, and instead of dereferencing symlinks, Git tries to read them and print where they point to. That doesn't work in this case because the symlinks are symlinks to anonymous pipes, which can't be resolved.

On other systems, the behaviour may be different because those files may be represented differently.

My patch attempted to solve this by simply opening the contents instead of stat'ing them as normal, but I think we found some edge cases and it didn't get finished. Note that this behaviour is what plain diff does because it doesn't handle symlinks at all.

-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA

Johannes Schindelin· Mar 27, 2023, 09:38 UTC · re: brian m. carlson · lore

Re: Redirect isn't working:

Hi brian & Jack,

On Fri, 20 Jan 2023, brian m. carlson wrote:

Show 39 quoted lines

> On 2023-01-19 at 18:06:17, Jack Adrian Zappa wrote:
> > Here is the filled out form for submitting a bug report:
> >
> > What did you do before the bug happened? (Steps to reproduce your issue)
> >
> >   At the command line, I typed the following command:
> >
> >   $ git diff --no-index --word-diff --color=always <(od -An -t x1
> > -w10000000000 file1.txt) <(od -An -t x1 -w10000000000 file2.txt)
> >
> > What did you expect to happen? (Expected behavior)
> >
> >   I expected to see the diff of the two files.
> >
> > What happened instead? (Actual behavior)
> >
> >   Instead I saw this:
> >
> >   error: Could not access '/proc/1961/fd/63'
> >
> > What's different between what you expected and what actually happened?
> >
> >   The difference is that I would get the difference between the two
> > files as opposed to a critical failure message.
>
> Thanks for the report.  This has come up before (and I attempted a
> patch), but the ultimate problem here is that the /proc/PID/fd/* files
> are symlinks on Linux, and instead of dereferencing symlinks, Git tries
> to read them and print where they point to.  That doesn't work in this
> case because the symlinks are symlinks to anonymous pipes, which can't
> be resolved.
>
> On other systems, the behaviour may be different because those files may
> be represented differently.
>
> My patch attempted to solve this by simply opening the contents instead
> of stat'ing them as normal, but I think we found some edge cases and it
> didn't get finished.  Note that this behaviour is what plain diff does
> because it doesn't handle symlinks at all.

Please note that this is not about a bug in Git itself, but in the MSYS2 Bash that Git for Windows includes in its distribution.

The technical details are quite involved, and I wrote up a ticket here, in case somebody is up for a real good challenge: https://github.com/git-for-windows/git/issues/4266

Ciao, Johannes