[Q] how to use logcat question, Please explain some simple questions - G Tablet Q&A, Help & Troubleshooting

Hello guys,
I have done my level best research but stuck at some simple steps. My goal is to see a logcat from a application for troubleshoot. This is what I have done so far. I have a laptop running on Ubuntu 12.04 32 bit. I followed this link https://help.ubuntu.com/community/AndroidSDK and have SDK manager running successfully.
I have usb debugging enabled on my G-tablet. after connecting tablet and running the command "adb devices" the laptop recognize my device.
then I run the command " adb logcat > logcat.txt " just like explained on this link http://forum.xda-developers.com/showthread.php?t=1616059
after running the above command I noticed a file in my home folder (laptop) named logcat.txt but the file contains only this "Unable to open log device '/dev/log/main': No such file or directory"
So here comes my silly questions:
1.) am I missing something obvious?
2.) If i want to see a log of what is happening when I run a particular application , How do i do it?
3.) Do I have to run SDK manager at the same time I am trying to run adb command? (i mean on background)
OH I have many more questions ,, but for now, please answer above.

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theteju said:
after running the above command I noticed a file in my home folder (laptop) named logcat.txt but the file contains only this "Unable to open log device '/dev/log/main': No such file or directory"
Click to expand...
Click to collapse
That looks like a problem on the ROM. Either a misconfigured kernel or the ROM not setting up the log devices correctly. What's the output of this command on the device?
Code:
$ [B]ls -l /dev/log[/B]

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crw-rw-rw- root log 10, 47 2013-01-29 11:10 events
crw-rw-rw- root log 10, 46 2013-01-29 11:10 radio
crw-rw-rw- root log 10, 45 2013-01-29 11:10 system
thats the output on my tablet running the command you mentioned.

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theteju said:
crw-rw-rw- root log 10, 47 2013-01-29 11:10 events
crw-rw-rw- root log 10, 46 2013-01-29 11:10 radio
crw-rw-rw- root log 10, 45 2013-01-29 11:10 system
Click to expand...
Click to collapse
And there you have it. The main device is non-existent--as the error message stated. Plus, the major and minor device numbers seem wrong.
What's the output of this command?
Code:
$ [B]su[/B]
# [B]strings /init | fgrep log/[/B]
/dev/log/
/dev/log/main
/dev/log/radio

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same as yours.
/dev/log/
/dev/log/main
/dev/log/radio

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so what is going on with my system? Am I looking at clean flash?

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theteju said:
same as yours.
/dev/log/
/dev/log/main
/dev/log/radio
Click to expand...
Click to collapse
Next:
Reboot the device and post the output of this command:
Code:
$ [B]dmesg | fgrep logger[/B]
[ 13.343038] logger: created 64K log 'log_main'
[ 13.343216] logger: created 256K log 'log_events'
[ 13.343395] logger: created 64K log 'log_radio'
[ 13.343574] logger: created 64K log 'log_system'

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[email protected]:/ $ su
[email protected]:/ # dmesg | fgrep logger
<6>[ 1.969399] logger: created 256K log 'log_main'
<6>[ 1.969608] logger: created 256K log 'log_events'
<6>[ 1.969750] logger: created 256K log 'log_radio'
<6>[ 1.969899] logger: created 256K log 'log_system'
[email protected]:/ #

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sorry I am being impatient. and Thanks for your prompt replies..I understand its too late @ your end now.

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theteju said:
I understand its too late @ your end now.
Click to expand...
Click to collapse
Well, I *was* a bit sleepy, but, now that you've tossed this bizarre problem onto my lap, I'm feeling decidedly perky. Next:
Code:
$ su
# [B]ls -l /sys/class/misc/ /sys/devices/virtual/misc/ | fgrep log_[/B]
lrwxrwxrwx 1 root root 0 Jan 29 23:45 log_events -> ../../devices/virtual/misc/log_events
lrwxrwxrwx 1 root root 0 Jan 29 23:45 log_main -> ../../devices/virtual/misc/log_main
lrwxrwxrwx 1 root root 0 Jan 29 23:45 log_radio -> ../../devices/virtual/misc/log_radio
lrwxrwxrwx 1 root root 0 Jan 29 23:45 log_system -> ../../devices/virtual/misc/log_system
drwxr-xr-x 3 root root 0 Jan 29 23:45 log_events
drwxr-xr-x 3 root root 0 Jan 29 23:45 log_main
drwxr-xr-x 3 root root 0 Jan 29 23:45 log_radio
drwxr-xr-x 3 root root 0 Jan 29 23:45 log_system
Also repeat the "ls -l /dev/log" command in post #2.

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/devices/virtual/misc/ | fgrep log_ <
lrwxrwxrwx root root 2013-01-29 13:52 log_events -> ../../devices/virtual/misc/log_events
lrwxrwxrwx root root 2013-01-29 13:52 log_main -> ../../devices/virtual/misc/log_main
lrwxrwxrwx root root 2013-01-29 13:52 log_radio -> ../../devices/virtual/misc/log_radio
lrwxrwxrwx root root 2013-01-29 13:52 log_system -> ../../devices/virtual/misc/log_system
drwxr-xr-x root root 2013-01-29 13:52 log_events
drwxr-xr-x root root 2013-01-29 13:52 log_main
drwxr-xr-x root root 2013-01-29 13:52 log_radio
drwxr-xr-x root root 2013-01-29 13:52 log_system
[email protected]:/ #
Sent from my Malata SMBA1002 using xda app-developers app

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[email protected]:/ # ls -l /dev/log
crw-rw-rw- root log 10, 47 2013-01-29 13:12 events
crw-rw-rw- root log 10, 46 2013-01-29 13:12 radio
crw-rw-rw- root log 10, 45 2013-01-29 13:12 system
[email protected]:/ #
Sent from my Malata SMBA1002 using xda app-developers app

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theteju said:
[email protected]:/ # ls -l /dev/log
crw-rw-rw- root log 10, 47 2013-01-29 13:12 events
crw-rw-rw- root log 10, 46 2013-01-29 13:12 radio
crw-rw-rw- root log 10, 45 2013-01-29 13:12 system
[email protected]:/ #
Click to expand...
Click to collapse
You did reboot the device like I asked you to, right?
Next:
Code:
$ [B]su[/B]
# [B]for f in /sys/class/misc/log_*/dev[/B]
> [B]do[/B] [B]echo $f: $(cat $f)[/B]
> [B]done[/B]
/sys/class/misc/log_events/dev: 10:46
/sys/class/misc/log_main/dev: 10:47
/sys/class/misc/log_radio/dev: 10:45
/sys/class/misc/log_system/dev: 10:44

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Yes I did reboot.
[email protected]:/ # for f /sys/class/misc//log_*/dev
sh: syntax error: '/sys/class/misc//log_*/dev' unexpected
[email protected]:/ # echo $f: $(cat $f)
done
The terminal is stuck with last command.
Sent from my Malata SMBA1002 using xda app-developers app

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I think I am doing something really stupid. Please make the commands in bold only.

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The commands are in bold. You've missed out the `in' and 'do' keywords. Close the Term window and retype.
You should also be able to use adb: "adb logcat" doesn't work, however, "adb shell" should.

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[email protected]:/ $ su
[email protected]:/ # for f in /sys/class/misc/log_*/dev
> do echo $f: $(cat $f)
> done
/sys/class/misc/log_events/dev: 10:47
/sys/class/misc/log_main/dev: 10:48
/sys/class/misc/log_radio/dev: 10:46
/sys/class/misc/log_system/dev: 10:45
[email protected]:/ #

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rajeevvp said:
The commands are in bold. You've missed out the `in' and 'do' keywords. Close the Term window and retype.
You should also be able to use adb: "adb logcat" doesn't work, however, "adb shell" should.
Click to expand...
Click to collapse
Does android SDK has to run on background on laptop to use adb?

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cool I am in adb shell, makes life more easy..

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Next:
Code:
$ [B]su[/B]
# [B]cat /sys/class/misc/log_*/uevent
[/B]MAJOR=10
MINOR=46
DEVNAME=log_events
MAJOR=10
MINOR=47
DEVNAME=log_main
MAJOR=10
MINOR=45
DEVNAME=log_radio
MAJOR=10
MINOR=44
DEVNAME=log_system
---------- Post added at 01:18 AM ---------- Previous post was at 01:16 AM ----------
theteju said:
Does android SDK has to run on background on laptop to use adb?
Click to expand...
Click to collapse
On Linux, you only need the adb binary to run adb commands. You don't need the entire Android SDK.