a few bash techniques for error handling

funcs.sh

#!/usr/bin/bash

trap "echo inner ERR" ERR
trap "echo inner EXIT" EXIT

aThunk()
{
        unsurprisingly
}

doIts()
{
        aThunk | cat ; echo "dollar zero: $?"
        echo $very
        aThunk | obviously ; echo "dollar zero: $?"
        echo $thisIs theEnd
}

doIts

test.sh

#!/usr/bin/bash

trap "echo outter ERR" ERR
trap "echo outter EXIT" EXIT

setMode()
{
        echo set "$*"
        eval set "$*"
        export SHELLOPTS
}

DEFAULTS=$(set +o)
MODES=("-o pipefail" "-u" "-e" "-Ee")

echo "baseline (default options) "
./funcs.sh ; echo ''
for i in `seq 1 ${#MODES[@]}`;
do
        echo -n "Test $i: "
        setMode ${MODES[$i-1]}
        ./funcs.sh || true
        echo ''; eval ${DEFAULTS}; export SHELLOPTS
done

Looks like:

$ ./test.sh
baseline (default options)
./funcs.sh: line 8: unsurprisingly: command not found
dollar zero: 0

./funcs.sh: line 15: obviously: command not found
./funcs.sh: line 8: unsurprisingly: command not found
dollar zero: 127
theEnd
inner EXIT

Test 1: set -o pipefail
./funcs.sh: line 8: unsurprisingly: command not found
dollar zero: 127

./funcs.sh: line 15: obviously: command not found
./funcs.sh: line 8: unsurprisingly: command not found
dollar zero: 127
theEnd
inner EXIT

Test 2: set -u
./funcs.sh: line 8: unsurprisingly: command not found
dollar zero: 127
./funcs.sh: line 14: very: unbound variable
inner EXIT

Test 3: set -e
./funcs.sh: line 8: unsurprisingly: command not found
inner EXIT

Test 4: set -Ee
./funcs.sh: line 8: unsurprisingly: command not found
inner ERR
inner ERR
inner EXIT

outter EXIT