silence-unless-failed

#!/bin/bash
# Executes the given command, silencing all its output.
# Its output is only printed to STDERR if the command failed.
#
# The output of the given command is buffered in a temporary file.
# You can also invoke this tool with the following parameters:
#   -f FILENAME   Buffer to a specific file. The file is truncated on opening.
#   -a FILENAME   Like -a, but appends to the file.

if [[ "$1" == "-f" ]]; then
	buffer_file="$2"
	should_delete=0
	should_append=0
	shift
	shift
elif [[ "$1" == "-a" ]]; then
	buffer_file="$2"
	should_delete=0
	should_append=1
	shift
	shift
else
	buffer_file=`mktemp /tmp/buffer.XXXXXXXXXX`
	should_delete=1
	should_append=0
fi

function cleanup()
{
	pids=$(jobs -p)
	if [[ "$pids" != "" ]]; then
		kill $pids
	fi
	if [[ $should_delete = 1 ]]; then
		rm -f "$buffer_file"
	fi
}

trap cleanup EXIT

if [[ $should_append = 1 ]]; then
	"$@" >>"$buffer_file" 2>&1
	exit_code=$?
else
	"$@" >"$buffer_file" 2>&1
	exit_code=$?
fi

if [[ $exit_code != 0 ]]; then
	cat "$buffer_file" >&2
fi
exit $exit_code