How to treat strings with spaces as a whole in bash?

Question

I'd like to build an error handler which will make an empty file marked with the error_occur time.

The core idea is to use the result of date command as a parameter.

I did:

time_stamp=$(date)
touch $time_stamp

But this turns out to create a series of empty file like 2014, Wed, 11:15:20.

How to convert time_stamp to a whole string here?

Solution 1

You must double quote your variable:

time_stamp="$(date)"
touch "$time_stamp"

In this case, double quote in "$(date)" is not mandatory, but it's a good practice to do that. You can read this for more understanding.

Solution 2

cuonglm's answer solves the problem of creating a file with spaces in general, but the problem starts by using the default output from date.

If you ever want to use a date or date-time string as part of your file name you should always use the --rfc-3339 option (if on a recent GNU system) or an appropriate format string. This will give you file names that are sortable in a logical way. The --rfc-3339 option takes a parameter, use seconds, ns or date depending on the accuracy you want in the filename:

time_stamp="$(date --rfc-3339=seconds)"
touch "$time_stamp"

You can also get a specific string without any spaces and just the info that you need from date +FORMAT (use man date for details).

time_stamp="$(date +%Y%m%d-%H%M)"
touch "$time_stamp"

will give you a file with a name like 20141029-0944 with no spaces and give you the illusion that you don't need to quote. But you still do, as you'd still be invoking the split+glob operator which could still actually split if used in a context where $IFS has been changed from the default.

Comments

[nyuszika7h]

The output of date --rfc-3339=seconds still contains spaces, why not date --iso-8601=seconds (or just date -Iseconds)?

[Anthon]

@nyuszika7h That looks good and works for date on my Ubuntu 12.04 box, but neither man date nor date --help mentions it. So I hope that is good enough an excuse.

[nyuszika7h]

It appears to be undocumented on Debian too, but it's in the man page on Arch Linux. Not sure why.

[user1730706]

You do not need quotes on the first line unix.stackexchange.com/a/131784

[cuonglm]

@StevenPenny: Yes, of course, I also noted this in my answer.