Question

I am trying to write shell script to read the value from /sys/class/net/eth0/carrier but it’s giving me the “permission denied” exception . The command I am trying to write in the shell script is

sudo echo $(/sys/class/net/eth0/carrier)

What I also noticed is that I am getting the same exception when I logged in as root and tried this:

echo $(/sys/class/net/eth0/carrier)

Any help in trying to read the value executing the shell script is greatly appreciated.

Answer 1

The syntax you have tries to execute that file. If you want to contents of the file in a variable, do something like this (probably bash-only syntax):

foo=$(</sys/class/net/eth0/carrier)

Or (portable)

foo=$(cat /sys/class/net/eth0/carrier)

If you just want to print it out to stdout:

cat /sys/class/net/eth0/carrier