log in shell scripts
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In some scenarios, we need to store shell script console output to a log file.
In log4j, we can define two appenders, one for ConsoleAppender and the other
one for FileAppender. In console, we can use FIFO (named pipe) to redirect the
output to log files. Unfortunately, in sh/ksh, we have to do it manually.
Here is one implementation:
Step 1: define a utility shell function
shell_functions.sh
startLogging(){
if [ -p "/tmp/$$.fifo" ]; then
then 1
fi
logginTo=$1
mkfifo /tmp/$$.fifo
exec 3>&1 4>&2
tee "$1" < /tmp/$$.fifo >&3 & tpid=$!
exec > /tmp/$$.fifo 2>&1
echo "Logging started to $1" >&2
}
stopLogging(){
if [ -p "/tmp/$$.fifo" ]; then
echo "logfile written to ${loggingTo}" >&2
exec 1>&3 3>&- 2>&4 4>&-
wait $tpid
rm /tmp/$$.fifo
fi
}
Step 2: You can put it in a central place for all caller shell scripts.
in setenv.sh
if [ $VERBOSE -ne 0 ]; then
if [ -z "${RT_SCRIPT_LOGDIR}" ]; then
RT_SCRIPT_LOGDIR="${APP_LOG_DIR}/$(basename "$0").$(date
+"%Y%m%d_%H%M%S").log"
fi
startLogging "${RT_SCRIPT_LOGDIR}"
fi
Step 3: then include both utility script and common ‘setenv.sh’ in execution script.
in a real calling script
BASEDIR=$(cd $(dirname $0); pwd)
# pull in common shell functions
. $(dirname "$0")/shell_functions.sh
# stop logging on exit
trap "stopLogging" EXIT
. $(dirname "$0"/setenv.sh
