yes there is iostat and all the other fancy software but sometimes, it’s not possible to access the internet or install packages

so here is the poor man’s iotop in pure bash

v4

will give this output, in a bit flickering way

hostnamectl; # tested on
Operating System: Debian GNU/Linux trixie/sid
Kernel: Linux 6.12.12-amd64
Architecture: x86-64

# scripts could be stored here
mkdir /scripts
cd /scripts
# download it
wget https://dwaves.de/scripts/diskio.sh

# or copy paste (if wordpress js did not mess anything up)

vim /scripts/diskio.sh

#!/bin/bash

# iterates over every line in /proc/diskstats that does not start with loop*
# and tries to calculate read | write in MBytes/s according to sectors per second
# Declare an associative array to store device names and their sector read/write values
declare -A devices

# First pass: collect the device names and initial read/write sector values
while read -r line; do
    # Extract the device name (3rd column in /proc/diskstats)
    device=$(echo $line | awk '{print $3}')
    
    # Skip devices starting with 'loop'
    if [[ ! $device =~ ^loop ]]; then
        # Get read sectors (6th column) and write sectors (10th column)
        read_sectors=$(echo $line | awk '{print $6}')
        write_sectors=$(echo $line | awk '{print $10}')
        
        # Store the device's initial read and write sector values in the array
        devices["$device"]="$read_sectors,$write_sectors"
    fi
done < /proc/diskstats

# Wait for 1 second to measure sector changes
sleep 1

# Second pass: calculate read and write speeds for each device
for device in "${!devices[@]}"; do
    # Get the initial read/write sector values
    initial_read_sectors=$(echo ${devices[$device]} | cut -d',' -f1)
    initial_write_sectors=$(echo ${devices[$device]} | cut -d',' -f2)
    
    # Get the updated read/write sector values
    updated_line=$(grep " $device " /proc/diskstats)
    updated_read_sectors=$(echo $updated_line | awk '{print $6}')
    updated_write_sectors=$(echo $updated_line | awk '{print $10}')
    
    # Calculate the difference in sectors read and written
    read_sectors_diff=$((updated_read_sectors - initial_read_sectors))
    write_sectors_diff=$((updated_write_sectors - initial_write_sectors))
    
    # 1 sector = 512 bytes (verify with `lsblk -o NAME,PHY-SEC`)
    read_bytes=$((read_sectors_diff * 512))
    write_bytes=$((write_sectors_diff * 512))
    
    # Convert to MB/s
    read_mbps=$(echo "scale=2; $read_bytes / 1024 / 1024" | bc)
    write_mbps=$(echo "scale=2; $write_bytes / 1024 / 1024" | bc)
    
    # Display the results
    echo "$device | read $read_mbps MBytes/s | write $write_mbps MBytes/s"
done

# run it like
chmod +x /scripts/*.sh
while true; do clear; /scripts/diskio.sh | column -t | sort -t' ' -k1,1V; sleep 1; done

# example output
dm-0       |  read  0       MBytes/s  |  write  0       MBytes/s
dm-1       |  read  0       MBytes/s  |  write  0       MBytes/s
dm-2       |  read  0       MBytes/s  |  write  0       MBytes/s
nvme0n1    |  read  0       MBytes/s  |  write  0       MBytes/s
nvme0n1p1  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme0n1p2  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme0n1p3  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme1n1    |  read  0       MBytes/s  |  write  0       MBytes/s
nvme1n1p1  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme1n1p2  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme1n1p3  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme1n1p4  |  read  0       MBytes/s  |  write  0       MBytes/s
nvme1n1p5  |  read  0       MBytes/s  |  write  0       MBytes/s
sda        |  read  154.09  MBytes/s  |  write  0       MBytes/s
sda1       |  read  139.09  MBytes/s  |  write  0       MBytes/s
sdb        |  read  0       MBytes/s  |  write  168.79  MBytes/s
sdb1       |  read  0       MBytes/s  |  write  161.86  MBytes/s
sdc        |  read  0       MBytes/s  |  write  0       MBytes/s
sdc1       |  read  0       MBytes/s  |  write  0       MBytes/s
sr0        |  read  0       MBytes/s  |  write  0       MBytes/s

pretty neat eh?

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