File system problems under Mini-Unix

[Béla Bréda]

Hi everyone,

I'm trying to write small C programs under Mini-Unix, but I'm experiencing some very strange things. I create the source file with 'ed', but when I reopen it, 'ed' only reads part of the file. The beginning of the file is missing, but part of the end is duplicated. Of course, 'cc' gives errors because it can't read the source code properly either. However, today when I booted up the system, the file suddenly got fixed. However, the problem returned after a while. If I make a copy of the "damaged" file, it works fine. 'ed' reads it completely and I can compile it with 'cc'. However, suddenly I can't run the compiled binary files. The system can't find them, while 'ls' shows that they are there. Out of curiosity, I list them with 'cat'. The binary content and a previously edited source code appear mixed up! As if something is mixed up in the file system. It's a pain, because what worked before, doesn't work anymore. I copy and delete files, hoping that they'll magically heal. Has anyone experienced anything like this? I can't decide if it's a malfunction of the operating system that's causing these mysterious errors or RK disk emulation? It seems to only happen with files that I've created. I haven't had any problems with the ones that were originally on the disk image. Is there a command under Mini-Unix that can check for and possibly fix file system errors?

Regards,

Béla

[cub...@gmail.com]

I would expect the usual 6th edition file system check programs to be there, like icheck and ncheck and maybe one or two others.  Just for grins, something you might try is after editing the file doing a sync command.  If somehow there is some caching going on within simh that’s confusing things that should probably prevent it from happening.

Also, foing a sync command before shutting down or stopping the CPU is essential on these old UNIXes.

JRJ

Sent from my iPhone

On Sep 24, 2025, at 2:40 PM, Béla Bréda <bela.b...@gmail.com> wrote:

Hi everyone,

I'm trying to write small C programs under Mini-Unix, but I'm experiencing some very strange things. I create the source file with 'ed', but when I reopen it, 'ed' only reads part of the file. The beginning of the file is missing, but part of the end is duplicated. Of course, 'cc' gives errors because it can't read the source code properly either. However, today when I booted up the system, the file suddenly got fixed. However, the problem returned after a while. If I make a copy of the "damaged" file, it works fine. 'ed' reads it completely and I can compile it with 'cc'. However, suddenly I can't run the compiled binary files. The system can't find them, while 'ls' shows that they are there. Out of curiosity, I list them with 'cat'. The binary content and a previously edited source code appear mixed up! As if something is mixed up in the file system. It's a pain, because what worked before, doesn't work anymore. I copy and delete files, hoping that they'll magically heal. Has anyone experienced anything like this? I can't decide if it's a malfunction of the operating system that's causing these mysterious errors or RK disk emulation? It seems to only happen with files that I've created. I haven't had any problems with the ones that were originally on the disk image. Is there a command under Mini-Unix that can check for and possibly fix file system errors?

Regards,

Béla

--
You received this message because you are subscribed to the Google Groups "UniBone" group.
To unsubscribe from this group and stop receiving emails from it, send an email to unibone+u...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/unibone/1e22755a-738c-421e-a40b-40c931c96a2fn%40googlegroups.com.

[Béla Bréda]

I tried sync. As an experiment, I ran it after every file write operation, but I didn't notice any difference.
By the way, I'm using a PDP-11/05, not simh.