Function to get specified key from /proc/cpuinfo

Question

On Linux, the file /proc/cpuinfo returns a set of key-value pairs, where the key and value are separated by a colon and each pair has its own line. It's a bit more complicated than that in reality, but for my needs that's as complicated as it needs to be. (I have only one processor core.)

My goal is to write a function in bash that takes the key for one of those items and returns the value corresponding to that key. Here's my current function:

function get_cpuinfo_prop () {
    TARGET_LINE=$(cat /proc/cpuinfo | grep ^$1)
    IFS=':'
    read -ra PARTS <<< "$TARGET_LINE"
    PROP_VALUE=${PARTS[1]}
    echo $PROP_VALUE
}

And you'd call it like this:

$(get_cpuinfo_prop 'key_name')

Is there a better way of doing it? How could I improve this code? Additionally, I think this might be returning extra whitespace before the actual value. How can I trim those characters off the beginning/end?

Answer 1

Useless use of cat

Grep can open files all by itself, cat isn't necessary in most circumstances. Also, quote everything - that's save you some debugging when you need to handle spaces in them - like for the "model name" property.

target_line=$(grep -m1 ^"$1" /proc/cpuinfo)

-m1 to stop at the first match, so you won't get weird results when you run your script on a machine with more CPUs. That's not portable unfortunately (not in POSIX), so if you don't have that, the usual options are: pipe to head -n 1, use awk instead and exit early, sed and exit early. The latter two can do it all in one go too.

Use your shells string manipulations for simple things

Assuming you want everything after the :, you can simply do:

value="${target_line##*: }"

See How do I do string manipulations in bash? for more like this, or the POSIX parameter expansion reference.

function keyword not necessary

It's less portable and doesn't buy you anything, so just omit it. See difference between “function foo() {}” and “foo() {}” for more details.

Variable names don't need to be in all caps

Personal preference of course, but especially for locals, lowercase is good - keep uppercase for globals/environment variables.

So:

get_cpuinfo_prop () {
  target_line=$(grep -m1 ^"$1" /proc/cpuinfo)
  echo "${target_line##*: }"
}