detect multi session cd

khairil · 11-16-2006, 10:35 PM

i am writing a bash shell script to automate cd burning. what i'm trying to do is,
1. if a user insert a blank cd it will burn with multi session (new multi session).
2. if not the script will try to detect whether the disc inserted is multi session disc or not.
3. if the disc is multi session disc then the script will continue writing with next session.

however i have difficulty to detect if the disc is multi session disc.

using the code from http://mlug.missouri.edu/~rjudd/proj...d/README.multi

for new disc;

Code:

icsb:/home/khairil # cdrecord -msinfo dev=1,0,0
cdrecord: Input/output error. read toc: scsi sendcmd: no error
CDB:  43 00 01 00 00 00 00 00 04 00
status: 0x2 (CHECK CONDITION)
Sense Bytes: 70 00 05 00 00 00 00 0A 00 00 00 00 24 00 00 00
Sense Key: 0x5 Illegal Request, Segment 0
Sense Code: 0x24 Qual 0x00 (invalid field in cdb) Fru 0x0
Sense flags: Blk 0 (not valid)
cmd finished after 0.000s timeout 40s
cdrecord: Cannot read session offset

for multi session disc

Code:

icsb:/home/khairil # cdrecord -msinfo dev=1,0,0
0,11702

how do i make my script detect a multi session disc?

thx!

ZeromusM · 11-17-2006, 07:51 AM

One possible way to do it might be to test against the exit status of the command instead of its output.

Code:

cdrecord -msinfo dev=1,0,0 &> /dev/null
if [ $? -eq 0 ]
then
  .....

The $? variable contains the exit status of the last command. This is just an idea for you to try, it may not work if, for example, the script gives you the same exit status either way.

khairil · 11-17-2006, 10:16 AM

Quote:

Originally Posted by ZeromusM

The $? variable contains the exit status of the last command. This is just an idea for you to try, it may not work if, for example, the script gives you the same exit status either way.

yes exactly! i tried this method before..

is there anyway i can count line of the output

Code:

cdrecord -msinfo dev=1,0,0

what i thought is;
- if that command runs on MULTI SESSION cd the output of the command will be just ONE LINE
- the same command if runs on NON MULTI SESSION cd will return MORE THAN ONE LINE..

or if there is better ways please let me know.

thx!

ZeromusM · 11-17-2006, 10:33 AM

A simple way to count lines would be:

Code:

cdrecord -msinfo dev=1,0,0 2>&1 | wc -l

Alternately, you could leave out the redirect to omit STDERR from the word count. This is pretty simple logic though, so I'd test it with all the different situations you might run into just to make sure the program reacts as expected.

You could also try counting only STDERR.

fvu · 11-18-2006, 02:36 AM

Hi, I'm using the bash function getCdInfo() underneath to determine if a CD is multi-session.

It's part of a complete bash script to create a nightly dar backup and write it to cdrw. You can see the full script here:
http://www.fvue.nl/wiki/Bash:_Backup_on_cdrw

Hope this helps,

Freddy Vulto

Code:

# Get info from current loaded cd
# @param string $1  Name of device containing the cd.
# @return
# @global string $cdIsMultiSession  1 if cd is multi-session, 0 if not
# @global string $cdMultiSessionInfo  Format: last_sess_start,next_sess_start
#    The first number is the sector number of the first sector in the last 
#    session of the disk that should be appended to.  The second number is 
#    the starting sector number of the new session.
#    Example values are:
#    0,-1       : readonly CD
#    0,24448    : multi-session CD with one previous session
#    null       : blank CD:
# @global integer $cdLastSessionStart  Starting sector number of last successful written session.
# @global integer $cdNextSessionStart  Starting sector number of new session.
# @global integer $cdNextSessionNr     Session number of new session, origin = 0.
#
# This software is released under the terms of the GNU General Public License.
# Copyright (C) 2006  Freddy Vulto
#
# The latest version of this software can be obtained here:
# http://www.fvue.nl/wiki/Bash:_Backup_on_cdrw
#
function getCdInfo() {
        # Retrieve maximum number of blocks on cd
    cdMaxNrOfBlocks=`\
        sudo cdrecord dev=$1 -atip 2> /dev/null |\
        sed -rn 's/^  ATIP start of lead out: ([0-9]+).*/\1/ p'`
    cdIsMultiSession=1
    cdLastSessionStart=
    cdMkisofsMultiSessionOptions=
    cdMultiSessionInfo=`sudo cdrecord -msinfo dev=$1`
    cdNextSessionNr=0
    cdNextSessionStart=
    if [ $cdMultiSessionInfo ]; then
        cdLastSessionStart="`echo $cdMultiSessionInfo | awk -F, '{ print $1 }'`"
        cdNextSessionStart="`echo $cdMultiSessionInfo | awk -F, '{ print $2 }'`"
        cdMkisofsMultiSessionOptions="-C $cdMultiSessionInfo -M $1"
        cdNextSessionNr=2  # Or greater...
        if (( $cdNextSessionStart == -1 )); then
            cdIsMultiSession=0
        elif (( $cdLastSessionStart == 0 )); then
            cdNextSessionNr=1
        fi
    fi
} # getCdInfo()

khairil · 11-28-2006, 08:47 PM

wow!

that's really cool!

thanks to all.. i can now finalize my script!