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01-29-2010, 05:20 PM
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#1
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LQ Newbie
Registered: Jan 2010
Posts: 21
Rep:
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Advice on contents of /dev/
I use ubuntu 9.10. I expected a "hexdump" of the files in /dev/ (on my system the directory is /dev/.udev/db) to give me a stream of bytes that are actually going in or out of various devices. Instead I get tiny little blocks or complaints that the file is not there if it is a link. Why doesn't this work?
Code:
root@server:/dev/.udev/db# hexdump -x net:eth0 0000000 3a45 4449 565f 4e45 4f44 5f52 5246 4d4f
0000010 445f 5441 4241 5341 3d45 4956 2041 6554
0000020 6863 6f6e 6f6c 6967 7365 202c 6e49 2e63
0000030 450a 493a 5f44 4f4d 4544 5f4c 5246 4d4f
0000040 445f 5441 4241 5341 3d45 5456 3136 3230
0000050 5b20 6852 6e69 2d65 4949 0a5d 3a45 4449
0000060 425f 5355 703d 6963 450a 493a 5f44 4556
0000070 444e 524f 495f 3d44 7830 3131 3630 450a
0000080 493a 5f44 4f4d 4544 5f4c 4449 303d 3378
0000090 3630 0a35
0000094
root@server:/dev/.udev/db# hexdump -x input:mice
hexdump: input:mice: No such file or directory
root@server:/dev/.udev/db# ls
block:fd0 misc:agpgart tty:tty15 tty:tty57
block:loop0 misc:binder tty:tty16 tty:tty58
block:loop1 misc:cpu_dma_latency tty:tty17 tty:tty59
block:loop2 misc:device-mapper tty:tty18 tty:tty6
block:loop3 misc:ecryptfs tty:tty19 tty:tty60
block:loop4 misc:fuse tty:tty2 tty:tty61
block:loop5 misc:hpet tty:tty20 tty:tty62
block:loop6 misc:mcelog tty:tty21 tty:tty63
block:loop7 misc:network_latency tty:tty22 tty:tty7
block:ram0 misc:network_throughput tty:tty23 tty:tty8
block:ram1 misc:pktcdvd tty:tty24 tty:tty9
block:ram10 misc:psaux tty:tty25 tty:ttyS0
block:ram11 misc:rfkill tty:tty26 tty:ttyS1
block:ram12 misc:snapshot tty:tty27 tty:ttyS2
block:ram13 net:eth0 tty:tty28 tty:ttyS3
block:ram14 ppdev:parport0 tty:tty29 usbmon:usbmon0
block:ram15 ppp:ppp tty:tty3 usbmon:usbmon1
block:ram2 printer:lp0 tty:tty30 usbmon:usbmon2
block:ram3 rtc:rtc0 tty:tty31 usbmon:usbmon3
block:ram4 scsi_generic:sg0 tty:tty32 usbmon:usbmon4
block:ram5 scsi_generic:sg1 tty:tty33 usbmon:usbmon5
block:ram6 scsi_generic:sg2 tty:tty34 usb:usb1
block:ram7 sound:adsp tty:tty35 usb:usb2
block:ram8 sound:audio tty:tty36 usb:usb3
block:ram9 sound:card0 tty:tty37 usb:usb4
block:sda sound:controlC0 tty:tty38 usb:usb5
block:sda1 sound:dsp tty:tty39 vc:vcs
block:sda2 sound:mixer tty:tty4 vc:vcs1
block:sda5 sound:pcmC0D0c tty:tty40 vc:vcs2
block:sr0 sound:pcmC0D0p tty:tty41 vc:vcs3
block:sr1 sound:pcmC0D1c tty:tty42 vc:vcs4
drm:card0 sound:pcmC0D1p tty:tty43 vc:vcs5
input:event0 sound:seq tty:tty44 vc:vcs6
input:event1 sound:sequencer tty:tty45 vc:vcs7
input:event2 sound:sequencer2 tty:tty46 vc:vcs8
input:mice sound:timer tty:tty47 vc:vcsa
input:mouse0 tty:console tty:tty48 vc:vcsa1
mem:full tty:ptmx tty:tty49 vc:vcsa2
mem:kmsg tty:tty tty:tty5 vc:vcsa3
mem:mem tty:tty0 tty:tty50 vc:vcsa4
mem:null tty:tty1 tty:tty51 vc:vcsa5
mem:oldmem tty:tty10 tty:tty52 vc:vcsa6
mem:port tty:tty11 tty:tty53 vc:vcsa7
mem:random tty:tty12 tty:tty54 vc:vcsa8
mem:urandom tty:tty13 tty:tty55
mem:zero tty:tty14 tty:tty56
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01-29-2010, 08:26 PM
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#2
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LQ Newbie
Registered: Jan 2010
Posts: 21
Original Poster
Rep:
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bump
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01-29-2010, 10:43 PM
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#3
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LQ Newbie
Registered: Jan 2010
Posts: 21
Original Poster
Rep:
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This may not be the best forum for this question; it might be a complicated one. I thought there was some kind of basic lack of understanding on my part on what is in /dev/.
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01-30-2010, 02:04 PM
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#4
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LQ Newbie
Registered: Jan 2010
Posts: 21
Original Poster
Rep:
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bump
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01-30-2010, 02:15 PM
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#5
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Moderator
Registered: Nov 2002
Location: Kent, England
Distribution: Debian Testing
Posts: 19,192
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Per the LQ Rules, please do not bump your own thread until at least 24 hours have elapsed without a reply. Because the LQ membership is global, people in other time zones may not have seen this post yet, and thus it may take some time before a response is received.
http://www.linuxquestions.org/rules.php
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01-31-2010, 12:26 PM
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#6
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LQ Veteran
Registered: Jul 2006
Location: London
Distribution: PCLinuxOS, Salix
Posts: 6,185
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Further advice: bumping actually reduces the chance of getting answered, because it means your thread won't be found by those helpful people who routinely check for zero reply threads.
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01-31-2010, 12:52 PM
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#7
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LQ Veteran
Registered: Nov 2005
Location: Annapolis, MD
Distribution: Mint
Posts: 17,809
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[QUOTE=stonehinge03;3845464]I use ubuntu 9.10. I expected a "hexdump" of the files in /dev/ (on my system the directory is /dev/.udev/db) to give me a stream of bytes that are actually going in or out of various devices. Instead I get tiny little blocks or complaints that the file is not there if it is a link. Why doesn't this work?
hexdump reads the contents of a file, not the real-time data stream. Further, the contents of a device file is not the data going to/from a device.
What exactly are you trying to do?
(Also, in that directory, I don't seen anything remotely resembling what you show.)
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01-31-2010, 03:39 PM
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#8
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LQ Newbie
Registered: Jan 2010
Posts: 21
Original Poster
Rep:
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I apologize to this board. It has never failed to answer any question I have ever posed to it (I've used several names over the years) but this question I didn't properly research. First off: the directory /dev/.udev/db is something used by udev and I don't want to interfere with the workings of that in anyway.
What I am trying to do is to read the character blocks that the kernel abstracts the data streams of the hardware into. Is there a command/program that will enable me to see hexadecimal values of those things? And will that be hexadecimal representations of the actual data stream that is coming from the device in question?
Last edited by stonehinge03; 01-31-2010 at 06:10 PM.
Reason: didn't research it myself properly.
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