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Old 04-04-2008, 08:27 PM   #1
Registered: Apr 2004
Location: Hell, Arizona
Distribution: Slackware 14.1
Posts: 492

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How to capture output of system call that uses printk?

I have a simple system call that uses printk to output some text. I have a small c program that calls the system call. This works, and the desired text is output to the console. How can I capture this text? If I call my program with >somefile.txt, somefile.txt is blank. If I use script, I see the line that calls the c program, but the output from the system call does not appear. If I use script -c <myprogram>, same thing. I'm using a virtual machine via VMware, so I can't even capture the screen because AFAICT, VMware only captures .bmp files. So, how can I capture the output of a system call that uses printk?

Debian kernel.

Edit: FWIW, I was able to:

dmesg | tail > output.txt

to get the text I wanted. So I did what I needed to do - but why can't the output from printk be captured using script or > ?

Last edited by Ook; 04-04-2008 at 08:48 PM.
Old 04-23-2008, 11:22 PM   #2
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Registered: Oct 2003
Distribution: Fedora 25 Gnome (Wayland)
Posts: 5,132

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I am glad you solved it.

by any chance have you tried virtualbox vs vmware?

2) I am no expert but I assume you have read the kernel dox on kernel hacking?


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