Problems using the date command command in awk

Question

I am writing a section of awk code that reads a log file of this format:

[03/02/2020 10:01:01] SOME DATA [03/02/2020 10:05:25] SOME MORE DATA [03/02/2020 11:54:38] AND YET SOME DATA

etc.

I wish to determine the epoch timestamp by combining the data in fields $1 and $2 and including a space between them to satisfy the input format needed by the bash date command.

This is the section of code I have written:

cmd="date -d" substr($1,2,10) substr($2,1,8) " +%s" cmd | getline this_date print this_date

At the moment, when i run the script, i get this error...

date: invalid date ‘03/02/202010:01:01’ date: invalid date ‘03/02/202010:05:25’ date: invalid date ‘03/02/202011:54:38’

etc.

So it seems to me I am nearly there but, as expected, the date command wants a space between the date and time portions.

I have tried many ways to try and code a 'space' between substr($1,2,10) substr($2,1,8) in the first line of code above but each time I get an error.

Can anyone advise the best approach?

Do you have or can you get GNU awk? It has built in time functions that'd make this task easier and more efficient and since you're using GNU date for -d I suspect you do also have GNU awk (run awk --version if you're not sure). Which timezone are the dates in your log file? Which timezone will you be running the tool from? — Ed Morton
– Ed Morton, Commented Feb 7, 2020 at 16:17

tripleee · Accepted Answer · 2020-02-07 13:49:23Z

You are lacking a space between the two substrs you extract; and you need to add quotes to join them into a single string.

cmd="date -d \"" substr($1,2,10) " " substr($2,1,8) "\" +%s"

If you can use single quotes instead of double, that will simplify things a bit; but Awk scripts are often passed between single quotes, so I assumed you'd prefer double quotes here.

Just to spell this out, the command being run is

date -d "03/02/2020 10:01:01" +%s

which gets turned into

date -d 03/02/2020 10:01:01 +%s

once the shell is done parsing it. The quotes are necessary to preserve the argument to the -d option as a single string even though it contains a space. As such, this is more of a shell question than an Awk question really.

I'm guessing this is Apache log format; most sane programs produce computer-readable time stamps in their logs.

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