I have a mini CD (185MB) capacity. I read a couple places that I can get the CD size by using:
--> cdrecord -toc -dev=0,0,0
by looking at "ATIP start of lead out: 101567 (22:36/17)" and using the sector size i.e. 2048 I can calculate 101567 * 2048 = 208009216 bytes. As I understand it this is the over reported CDR capacity (the CD has 185 MB written on it) that can be used for overburn. The CDR I have is written in multisession mode so the output of "cdrecord -toc dev=0,0,0" is (shortened for space):

Using generic SCSI-3/mmc CD-R driver (mmc_cdr).
Driver flags : SWABAUDIO
Drive buf size : 1234944 = 1206 KB
01 00 00 01 00 00 00 00
01 AA 01 01 00 00 00 00
Current Secsize: 2048
---------
1995-2001 J?rg Schilling
TOC Type: 1 = CD-ROM
scsidev: '0,0,0'
scsibus: 0 target: 0 lun: 0
Linux sg driver version: 3.1.24
Using libscg version 'schily-0.5'
Using libscg transport code version 'schily-scsi-linux-sg.c-1.66'
atapi: 1
Device type : Removable CD-ROM
Version : 0
Response Format: 1
Vendor_info : '_NEC '
Identifikation : 'NR-7900A '
Revision : '1.08'
Device seems to be: Generic mmc CD-RW.
Disk sub type: Medium Type B, low Beta category (B-) (4)
ATIP start of lead in: -11644 (97:26/56)
ATIP start of lead out: 101567 (22:36/17)
Disk type: Short strategy type (Phthalocyanine or similar)
Manuf. index: 10
Manufacturer: Lead Data Inc.
first: 1 last 4
track: 1 lba: 0 ( 0) 00:02:00 adr: 1 control: 4 mode: 2
track: 2 lba: 21994 ( 87976) 04:55:19 adr: 1 control: 4 mode: 2
track: 3 lba: 29196 ( 116784) 06:31:21 adr: 1 control: 4 mode: 2
track: 4 lba: 36398 ( 145592) 08:07:23 adr: 1 control: 4 mode: 2
track:lout lba: 97938 ( 391752) 21:47:63 adr: 1 control: 4 mode: -1
CD-Text len: 4

How can I find the used space (in bytes) on the CDR? I need this information so that I can compare the amount of bytes I want to write to and deceide accordingly. Thanks for your help.