Append date and time to an environment variable in linux makefile

Question

In my Makefile I want to create an environment variable using the current date and time. Pseudo code:

LOG_FILE := $LOG_PATH + $SYSTEM_DATE + $SYSTEM_TIME

Any help appreciated - thanks.

Solution 1

you can use this:

LOGFILE=$(LOGPATH) `date +'%y.%m.%d %H:%M:%S'`

NOTE (from comments):

it will cause LOGFILE to be evaluated every time while used. to avoid that:

LOGFILE=$(LOGPATH)$(shell date)

Solution 2

You need to use the $(shell operation) command in make. If you use operation, then the shell command will get evaluated every time. If you are writing to a log file, you don't want the log file name to change every time you access it in a single make command.

LOGPATH = logs
LOGFILE = $(LOGPATH)/$(shell date --iso=seconds)

test_logfile:
    echo $(LOGFILE)
    sleep 2s
    echo $(LOGFILE)

This will output:

echo logs/2010-01-28T14:29:14-0800
logs/2010-01-28T14:29:14-0800
sleep 2s
echo logs/2010-01-28T14:29:14-0800
logs/2010-01-28T14:29:14-0800

Solution 3

you can use "date" command