1.\" 2.\" Copyright (c) 2001 Joerg Wunsch 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" 27.Dd November 16, 2025 28.Dt FDREAD 1 29.Os 30.Sh NAME 31.Nm fdread 32.Nd read floppy disks 33.Sh SYNOPSIS 34.Nm 35.Op Fl qr 36.Op Fl d Ar device 37.Op Fl f Ar fillbyte 38.Op Fl o Ar file 39.Nm 40.Op Fl d Ar device 41.Fl I Ar numsects 42.Op Fl t Ar trackno 43.Sh DEPRECATION NOTICE 44.Nm 45is deprecated and may not be present in 46.Fx 16.0 47and later. 48.Sh DESCRIPTION 49The 50.Nm 51utility reads floppy disks. 52Effective read blocking based on the track 53size is performed, and floppy-specific error recovery of otherwise 54bad blocks can be enabled. 55.Pp 56The 57.Nm 58utility 59will always read an entire floppy medium, and write its contents to 60the respective output file. 61Unlike other tools like 62.Xr dd 1 , 63.Nm 64automatically uses a read block size that is more efficient than 65reading single blocks (usually one track of data at a time), but 66falls back to reading single floppy sectors in case of an input/output 67error occurred, in order to obtain as much valid data as possible. 68While 69.Nm 70is working, kernel error reporting for floppy errors is turned off, so 71the console and/or syslog are not flooded with kernel error messages. 72.Pp 73The 74.Nm 75utility accepts the following options: 76.Bl -tag -width indent 77.It Fl q 78Turn on quiet mode. 79By default, the medium parameters of the device 80are being written to standard error output, progress will be indicated 81by the approximate number of kilobytes read so far, and errors will be 82printed out in detail, including the information about the location of 83recovered data in the output. 84In quiet mode, none of these messages 85will be generated. 86.It Fl r 87Enable error recovery. 88By default, 89.Nm 90stops after the first unrecovered read error, much like 91.Xr dd 1 92does. 93In recovery mode, however, one of two recovery actions will be 94taken: 95.Bl -bullet 96.It 97If the error was a CRC error in the data field, the 98kernel is told to ignore the error, and data are transferred to the 99output file anyway. 100.Bf -emphasis 101Note that this will cause the erroneous data 102to be included in the output file! 103.Ef 104Still, this is the best recovery action that can be taken at all. 105.It 106All other errors are really fatal (usually, the FDC did not find the 107sector ID fields), thus a dummy block with fill 108bytes will be included in the output file. 109.El 110.Pp 111Unless operating in quiet mode, the action taken and the location of 112the error in the output file will be displayed. 113.It Fl d Ar device 114Specify the input floppy device, defaulting to 115.Pa /dev/fd0 . 116The parameter 117.Ar device 118must be a valid floppy disk device. 119.It Fl f Ar fillbyte 120Value of the fill byte used for dummy blocks in the output file in 121recovery mode. 122Defaults to 123.Ql 0xf0 . 124(Mnemonic: 125.Dq foo . ) 126The value can be specified using the usual C language notation of 127the number base. 128.It Fl o Ar file 129Specify the output file to be 130.Ar file . 131By default, the data will be written to standard output. 132.It Fl I Ar numsects 133Read 134.Ar numsects 135sector ID fields, and write out their contents to standard output. 136Each sector ID field contains recorded values for the cylinder number 137.Pq Ql C , 138the head number 139.Pq Ql H , 140the record number (sector number starting with 1) 141.Pq Ql R , 142and the 143.Em sector shift value 144(0 = 128 bytes, 1 = 256 bytes, 2 = 512 bytes, 3 = 1024 bytes) 145.Pq Ql N . 146The 147.Fl I 148option is mutually exclusive with all other options except 149.Fl d Ar device 150and 151.Fl t Ar trackno . 152.It Fl t Ar trackno 153Specify the track number (cylinder number * number of heads + head 154number) to read the sector ID fields from; only allowed together with 155the 156.Fl I Ar numsects 157option. 158.El 159.Sh FILES 160.Bl -tag -width /dev/fd0 161.It Pa /dev/fd0 162Default device to read from. 163.El 164.Sh EXIT STATUS 165The 166.Nm 167utility sets the exit value according to 168.Xr sysexits 3 . 169In recovery mode, the exit value will be set to 170.Dv EX_IOERR 171if any error occurred during processing (even in quiet mode). 172.Sh DIAGNOSTICS 173Unless running in quiet mode, upon encountering an error, the status 174of the floppy disc controller (FDC) will be printed out, both in 175hexadecimal form, followed by a textual description that translates 176those values into a human-readable form for the most common error 177cases that can happen in a PC environment. 178.Pp 179The FDC error status includes the three FDC status registers 180.Ql ST0 , 181.Ql ST1 , 182and 183.Ql ST2 , 184as well as the location of the error (physical cylinder, head, and sector 185number, plus the 186.Dq sector shift value , 187respectively). 188See the manual for the NE765 or compatible for details 189about the status register contents. 190.Pp 191The FDC's status is then examined to determine whether the error is 192deemed to be recoverable. 193If error recovery was requested, the 194location of the bad block in the output file is indicated by its 195(hexadecimal) bounds. 196Also, a summary line indicating the total number 197of transfer errors will be printed before exiting. 198.Sh SEE ALSO 199.Xr dd 1 , 200.Xr fdwrite 1 , 201.Xr sysexits 3 , 202.Xr fdc 4 , 203.Xr fdcontrol 8 204.Sh HISTORY 205The 206.Nm 207utility was written mainly to provide a means of recovering at least some of 208the data on bad media, and to obviate the need to invoke 209.Xr dd 1 210with too many hard to memorize options that might be useful to handle 211a floppy. 212.Pp 213The command appeared in 214.Fx 5.0 . 215.Sh AUTHORS 216Program and man page by 217.An J\(:org Wunsch . 218.Sh BUGS 219Concurrent traffic on the second floppy drive located at the same FDC 220will make error recovery attempts pointless, since the FDC status 221obtained after a read error occurred cannot be guaranteed to actually 222belong to the erroneous transfer. 223Thus using option 224.Fl r 225is only reliable if 226.Ar device 227is the only active drive on that controller. 228.Pp 229No attempt beyond the floppy error retry mechanism of 230.Xr fdc 4 231is made in order to see whether bad sectors could still be read 232without errors by trying multiple times. 233.Pp 234Bits that are (no longer) available on the floppy medium cannot be 235guessed by 236.Nm . 237