wc: dmsetup create ioerr --table "0 8 error"; wc /dev/mapper/ioerr shows err on top

[oech3]

$ run0 dmsetup create ioerr --table "0 8 error"
$ run0 chmod 777 /dev/mapper/ioerr
$ uu-wc /dev/mapper/ioerr
wc: /dev/mapper/ioerr: Input/output error
      0       0       0 /dev/mapper/ioerr
$ gnu-wc
      0       0       0 /dev/mapper/ioerr
wc: /dev/mapper/ioerr: Input/output error

[oech3]

@pixelb Does this require LD_PRELOAD if (rootless) wc-io-err.sh test was added to GNU?

[pixelb]

Yes simulating errors on read would probably require LD_PRELOAD. so root dmapper would be preferable. Pity there isn't a more readily available device like /dev/full for read errors

[oech3]

Pity there isn't a more readily available device like /dev/full for read errors

I hyper agree.

[oech3]

uu-wc does not panic in this case:

$ strace -o /dev/null -P /tmp/a -e read -e fault=read:error=EIO:when=1 wc a
wc: a: Input/output error
0 0 0 a

If needed to extract OS provided err message, dmsetup might better than strace...

[oech3]

I think uutils is natural at here i.e. wc should show error 1st before showing info about file.