How to get permissions from code to use serial port

Posted on 2006-07-14
Medium Priority
Last Modified: 2012-05-05
I writing code to talk out the com port ttys0. When I run this code I am unable to open a port and get back a -1 from the open command. I've been told that under linux i need to somehow get permission from within my code to use the port. I'm tried excuting loggged in as root and still bo luck. Can anyone help?

When I run this same code under cygwin on a windows machine it works.
Question by:BlackRussian
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3

Expert Comment

ID: 17108878
You can easily use open, read, write and ioctl. The  permission bits in the device file needs to be arranged first.

you can grant the permission by issuing
chmod o+rw /dev/ttyS0

But you need to call ioperm(), if you are directly accessing hardware (like direct port programming.)

Manish Regmi

Expert Comment

ID: 17108900
If you are into I/O port programming, This howto is worth reading


Manish Regmi


Author Comment

ID: 17110032
Hi manish. The article shows using I/O ports. Do need to know what port 0x.. my serial port is to use this ?. is there a way to use /dev/ttys0 as a parameter?.

Accepted Solution

manish_regmi earned 800 total points
ID: 17110159
You need that only if you are accessing hardware directly. But the Linux kernel already have a serial device driver. You might not need to use it.

if you are interested see the serial port specs here

you can just use /dev/ttys0 interface and use open, read, write and ioctl

Manish Regmi

Featured Post

What is SQL Server and how does it work?

The purpose of this paper is to provide you background on SQL Server. It’s your self-study guide for learning fundamentals. It includes both the history of SQL and its technical basics. Concepts and definitions will form the solid foundation of your future DBA expertise.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The purpose of this article is to fix the unknown display problem in Linux Mint operating system. After installing the OS if you see Display monitor is not recognized then we can install "MESA" utilities to fix this problem or we can install additio…
The purpose of this article is to demonstrate how we can upgrade Python from version 2.7.6 to Python 2.7.10 on the Linux Mint operating system. I am using an Oracle Virtual Box where I have installed Linux Mint operating system version 17.2. Once yo…
If you’ve ever visited a web page and noticed a cool font that you really liked the look of, but couldn’t figure out which font it was so that you could use it for your own work, then this video is for you! In this Micro Tutorial, you'll learn yo…
Sometimes it takes a new vantage point, apart from our everyday security practices, to truly see our Active Directory (AD) vulnerabilities. We get used to implementing the same techniques and checking the same areas for a breach. This pattern can re…
Suggested Courses

764 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question