works with devices in /dev/*

hi,i am new in c programming and lately i have been wondering:

if in linux, all devices are considered as files, why some devices like usb webcam connected to linux machine are as not simple to open and use as opening a normal file in a c program?
ex: i connected a usb webcam on my linux(ubuntu) laptop and i tried to open it and read from it as normal file but i could work, and i wonder why i can open a camera as normal file and read from it if linux consider it as a file. thank you.

ps: i apologise in advance if i asked a stupid question .

Quote:

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i tried to open it and read from it as normal file but i could [not get it to] work

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What exactly did you do? (Post code/script.)
How exactly did it not work?

May be you need to have root Permissions to use usb-devices.
For example if you want to use an usb-stick with windows emulated on qemu-kvm
you need first to login as superuser.
Then, start terminal and type 'lsusb' to detect what for a bus and what for a device
you must use to access an usb-stick with an emulated operating system.

If you want to get only informations you can use 'lsusb' without root permissions.

I don't know if you can change the permissions with chmod for the device, but it is
possible that the permissions will change to the former status after a new start of
the system.

Quote:

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Originally Posted by j3ph

hi,i am new in c programming and lately i have been wondering:

if in linux, all devices are considered as files, why some devices like usb webcam connected to linux machine are as not simple to open and use as opening a normal file in a c program?

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Yep.. use open() to get a file desciptor and...

Quote:

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Originally Posted by j3ph

ex: i connected a usb webcam on my linux(ubuntu) laptop and i tried to open it and read from it as normal file but i could work, and i wonder why i can open a camera as normal file and read from it if linux consider it as a file. thank you.

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... there is a special syscall to deal with devices: ioctl(), to send "commands" to control the device. Those commands are device dependent...