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better handling of SIGINT / Ctrl-C #44

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54 changes: 13 additions & 41 deletions prettyping
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Original file line number Diff line number Diff line change
Expand Up @@ -198,52 +198,23 @@ parse_arguments "$@"

export LC_ALL=C

# Warning! Ugly code ahead!
# The code is so ugly that the comments explaining it are
# bigger than the code itself!
#
# Suppose this:
#
# cmd_a | cmd_b &
#
# I need the PID of cmd_a. How can I get it?
# In bash, $! will give me the PID of cmd_b.
#
# So, I came up with this ugly solution: open a subshell, like this:
#
# (
# cmd_a &
# echo "This is the PID I want $!"
# wait
# ) | cmd_b

# Ignore SIGINT (Ctrl-C) downstream of ping, so the pipeline can cleanly finish when ping is interrupted.

# Ignore Ctrl+C here.
# If I don't do this, this shell script is killed before
# ping and gawk can finish their work.
trap '' 2
"${PING_BIN}" "${PING_PARAMS[@]}" 2>&1 | (
trap '' INT

# Now the ugly code.
(
"${PING_BIN}" "${PING_PARAMS[@]}" &
PING_PID="$!"

# Commented out, because it looks like this line is not needed
#trap "kill -2 $PING_PID ; exit 1" 2 # Catch Ctrl+C here

wait
) 2>&1 | (
if [ "${IS_TERMINAL}" = 1 ]; then
# Print a message to notify the awk script about terminal size change.
trap "echo SIGWINCH" 28
trap 'echo SIGWINCH' WINCH
fi

# The trap must be in another subshell because otherwise it will interrupt
# the "wait" commmand.
while read line; do
echo -E "$line"
while read -r line; do
printf '%s\n' "$line"
done
) 2>&1 | "${AWK_BIN}" "${AWK_PARAMS[@]}" '
) 2>&1 | (
trap '' INT

"${AWK_BIN}" "${AWK_PARAMS[@]}" '
# Weird that awk does not come with abs(), so I need to implement it.
function abs(x) {
return ( (x < 0) ? -x : x )
Expand Down Expand Up @@ -478,12 +449,12 @@ function print_received_response(rtt, block_index) {
} else {
block_index = 1 + int((rtt - BLOCK_RTT_MIN) * (BLOCK_LEN - 2) / BLOCK_RTT_RANGE)
}
printf( BLOCK[block_index] )
printf( BLOCK[block_index] ESC_DEFAULT)
CURR_COL++
}

function print_missing_response(rtt) {
printf( ESC_RED "!" )
printf( ESC_RED "!" ESC_DEFAULT)
CURR_COL++
}

Expand Down Expand Up @@ -889,3 +860,4 @@ BEGIN {
# Not needed when the output is a terminal, but does not hurt either.
fflush()
}'
)