18.18"Cannot open /dev/ttyS?: Permission denied"

Check the file permissions on this port with "ls -l /dev/ttyS?"_ If you own the ttyS? then you need read and write permissions: crw with the c (Character device) in col. 1. It you don't own it then it will work for you if it shows rw- in cols. 8 & 9 which means that everyone has read and write permission on it. Use "chmod" to change permissions. There are more complicated (and secure) ways to get access like belonging to a "group" that has group permission.


Some programs change the permissions when they run but restore them when the program exists normally. But if someone pulls the plug on your PC it's an abnormal exit and correct permissions may not be restored.

* License

* Modem How-To Index