vttime

#!/bin/bash

# vttime. 
# Measure run time of any command on a VT terminal.

# Stops timing when the terminal responds to
# Device Status Request 5 (howyadoin?).

# Note, accuracy is far less than the precision indicated.
# It is probably closer to milliseconds, not nanoseconds.

# hackerb9 2024

if [[ -z "$0" ]]; then
    echo "Usage: vttime <command> [args...]" >&2
    exit 1
fi

declare -i ns=0 s=0 m=0 h=0
declare -i latency=0 i=0 start=0 end=0

# Attempt to subtract the latency of using Device Status Request 5.
# On a VT340 at 19200bps, the latency is under 30ms. (30,000,000 ns).
read -s -d "n" -p $'\e[5n'
start=$(date +%s%N)
read -s -d "n" -p $'\e[5n'
end=$(date +%s%N)
latency=end-start

printf "%12s: %'12d ns\n" "Latency" $latency

printf "%12s: " "Executing"
echo "$*"
read -s -d "n" -p $'\e[5n'	# Make sure terminal is ready.
start=$(date +%s%N)
"$@"				# Run the command
read -s -d "n" -p $'\e[5n'	# Wait for terminal to finish.
end=$(date +%s%N)
ns=end-start

ns=ns-latency			# Attempt correction
if (( ns < 0 )); then ns=0; fi

if (( ns > 1000000000 )); then
    s=ns/1000000000
    ns=ns%1000000000
fi
if (( s > 60 )); then
    m=s/60
    s=s%60
fi

exec >&2
printf "%12s: " "Run time"

if ((m>0)); then
    printf "%'12d m " $m 
fi

if ((s>0)); then
    printf "%'12d s " $s 
fi

printf "%'12d ns\n" $ns