How to invoke ioctl in shell script?

Question

I'm trying to execute an ioctl call on a system with only bash and primitive base utilities.

Is there any way to execute arbitrary ioctl command (if the params are simply integers) to a specific device file in /dev in shell script, without writing C / perl / python programs? Something like "magic_ioctl /dev/console 30 1 2" which would calls "ioctl(open("/dev/console"), 30, 1, 2);".

Being able to issue `ioctl` calls in, for example, init scripts on embedded devices (no perl/python), without having to deal with cross-compilation/deployment of a C program (just one line in the script!) would be really handy. Did you manage to get any further with this? — Anthony, Feb 24 '15 at 02:29

Jérôme Pouiller · Answer 1 · 2015-12-19T16:52:11.157

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I wrote ioctl tool exactly for this purpose: https://github.com/jerome-pouiller/ioctl.

Currently, it is not possible to pass multiple argument to ioctl call. Have you an example where it would be usefull?

If you want to call ioctl(open("/dev/console"), 30, 1);, you can run:

ioctl /dev/console 30 -v 1

However, for most ioctl, you want to allocate a buffer and pass a pointer to this buffer in argument to ioctl call. In this case, just forget -v. ioctl will read/write buffer content from/to standard input/output. ioctl try to guess buffer size and direction from ioctl number.

The best is: ioctl understand many (around 2200) ioctl symbolic names. Thus you can call:

ioctl /dev/video0 VIDIOC_QUERYCAP > video_caps

edited Dec 19 '15 at 16:52

answered Dec 19 '15 at 16:43

Jérôme Pouiller

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Found similarly named stock utility in my android 2.3 at /system/bin/ioctl. – ogurets Mar 25 '17 at 21:51
@ogurets: interesting, do you know where is source code of this utility? – Jérôme Pouiller Mar 26 '17 at 21:11
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I think this is the one: https://android.googlesource.com/platform/system/core/+/android-4.4_r1/toolbox/ioctl.c – ogurets Mar 26 '17 at 21:24
What if you want to run ioctl on an existing file descriptor without opening? – Pavel Šimerda Apr 23 '20 at 09:09
@PavelŠimerda No, it is not supported. However, the feature is not complicated.Patches welcome. Don't forget to provide a usage example (playing with file descriptors in shell is not obvious). – Jérôme Pouiller Apr 24 '20 at 07:29
Is this ioctl program still maintained? Looks like GitHub PRs are not being processed. – Alex D May 05 '20 at 20:59
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@AlexD Indeed, `ioctl` would need some attention. I will do the housework next week. – Jérôme Pouiller May 06 '20 at 11:05

score 7 · Answer 2 · answered Nov 27 '11 at 22:41

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Why you reject perl/c/python solutions ? You can made this by perl one-liner like this: perl -e require "sys/ioctl.ph"; ioctl(...);

answered Nov 27 '11 at 22:41

Sergey Beduev

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There are reasons. E.g. on my target platform, there's no perl/python at all. And creating a C program for this purpose is a bit cumbersome. – t7ko Dec 02 '16 at 19:18
I don't want to recompile the C everytime the system changes. – Andy_A̷n̷d̷y̷ Jul 28 '17 at 21:59

How to invoke ioctl in shell script?

2 Answers2