|-q||Turn on quiet mode. By default, the medium parameters of the device are being written to standard error output, progress will be indicated by the approximate number of kilobytes read so far, and errors will be printed out in detail, including the information about the location of recovered data in the output. In quiet mode, none of these messages will be generated.|
Enable error recovery.
stops after the first unrecovered read error, much like
In recovery mode, however, one of two recovery actions will be
Unless operating in quiet mode, the action taken and the location of the error in the output file will be displayed.
|Specify the input floppy device, defaulting to /dev/fd0. The parameter device must be a valid floppy disk device.|
|Value of the fill byte used for dummy blocks in the output file in recovery mode. Defaults to 0xf0. (Mnemonic: "foo.") The value can be specified using the usual C language notation of the number base.|
|Specify the output file to be file. By default, the data will be written to standard output.|
|Read numsects sector ID fields, and write out their contents to standard output. Each sector ID field contains recorded values for the cylinder number (C), the head number (H), the record number (sector number starting with 1) (R), and the sector shift value (0 = 128 bytes, 1 = 256 bytes, 2 = 512 bytes, 3 = 1024 bytes) (N). The -I option is mutually exclusive with all other options except -d device and -t trackno.|
|Specify the track number (cylinder number * number of heads + head number) to read the sector ID fields from; only allowed together with the -I numsects option.|
/dev/fd0 Default device to read from.
The fdread utility sets the exit value according to sysexits(3). In recovery mode, the exit value will be set to EX_IOERR if any error occurred during processing (even in quiet mode).
Unless running in quiet mode, upon encountering an error, the status of the floppy disc controller (FDC) will be printed out, both in hexadecimal form, followed by a textual description that translates those values into a human-readable form for the most common error cases that can happen in a PC environment.
The FDC error status includes the three FDC status registers ST0, ST1, and ST2, as well as the location of the error (physical cylinder, head, and sector number, plus the "sector shift value", respectively). See the manual for the NE765 or compatible for details about the status register contents.
The FDCs status is then examined to determine whether the error is deemed to be recoverable. If error recovery was requested, the location of the bad block in the output file is indicated by its (hexadecimal) bounds. Also, a summary line indicating the total number of transfer errors will be printed before exiting.
The fdread utility was written mainly to provide a means of recovering at least some of the data on bad media, and to obviate the need to invoke dd(1) with too many hard to memorize options that might be useful to handle a floppy.
The command appeared in
.Fx 5.0 .
Program and man page by
.An Jrg Wunsch .
Concurrent traffic on the second floppy drive located at the same FDC will make error recovery attempts pointless, since the FDC status obtained after a read error occurred cannot be guaranteed to actually belong to the erroneous transfer. Thus using option -r is only reliable if device is the only active drive on that controller.
No attempt beyond the floppy error retry mechanism of fdc(4) is made in order to see whether bad sectors could still be read without errors by trying multiple times.
Bits that are (no longer) available on the floppy medium cannot be guessed by fdread.