Getting Specific Value from Dmidecode Output with Bash Script

Question

Below is a section from the dmidecode output. There is a part of this section that I want to break down. I want to get the 4 bytes after pattern 01 85 30. And I want to change the byte order. Then I will compare with the hex strings I have.

....... 
Handle 0x0027, DMI type 219, 106 bytes
OEM-specific Type
 Header and Data:
 DB 6A 27 00 01 04 01 45 02 00 90 06 *01 85 30* 20
 00 00 00 00 40 00 00 03 1F 24 02 C9 02 60 44 02
 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
 FF FF FF FF FF FF FF FF 03 00 00 00 80 00 00 00
 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 00 04 FF FF FF FF FF FF FF FF FF FF FF FF FF FF
 FF FF FF FF FF FF FF FF FF FF
.......

I prepared a bash script and it works, is there a better way?

#!/bin/bash
id_array=("00000020", "00000040")
unique_id=$(dmidecode -t 219 | grep "01 85 30" -A 1 | xargs | cut -c 46-56 | tr -d '[:space:]' | grep -o .. | tac | paste -sd '' -)
if [[ " ${id_array[*]} " == *"$unique_id"* ]];
then
 echo "1"
else
 echo "0"
fi

Answer 1

Your script should work, but there is room for improvement. Instead of using grep and cut, you can use awk to extract the bytes after the pattern 01 85 30 and reverse their order. Here's an example:

unique_id=$(dmidecode -t 219 | awk '/01 85 30/ {getline; gsub(/ /,""); print substr(0,9,8ドル)}' | tac -rs ..)

This awk command searches for the pattern 01 85 30, reads the next line, removes all spaces, and prints the 4 bytes starting from the 9th position (which is after the 8-byte timestamp). The result is then piped to tac -rs .. to reverse the byte order.

In addition, you can simplify the array search by using parameter expansion instead of grep:

if [[ ${id_array[*]} =~ $unique_id ]]; then
 echo "1"
else
 echo "0"
fi

This tests whether the expanded array ${id_array[*]} contains the string $unique_id. The =~ operator is used for pattern matching.

• embeddedstack: Thanks your finger but not worked, after the pattern 01 85 30. There is a 20. But you eliminated it.
• Simon: @embedded4ever maybe add ` | tail -n1 | tac -rs ..` instead of just ` | tac -rs ..` ?
• embeddedstack: Nothing changed, because you have already eliminated once using getline.
• Simon: @embedded4ever oh, then print substr(0,11,8ドル)? sorry for guessing, I can't check that out for myself right now
• embeddedstack: i see, but not worked again :)