Re^4: Date/Time Manipulation

OK I have been looking at that statement

$stuff =~ s/ (\d\d)/sprintf(" %2.2i",$1-1)/e;

I have poured over my Perl O'Reilly book and am still clueless. Since the input lines look like this

2016-05-16 10:51:07 random text

How does the expression pick out the hours versus any other two digits?

Then what does the sprintf do? I'm willing to learn but would need a starting point.

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Re^5: Date/Time Manipulation by haukex (Archbishop) on May 25, 2016 at 18:47 UTC
Hi RobertJ, The regex picks those two digits because they're the only ones preceded by a space. As for the rest: because the `/e` modifier is used on the substitution, the replacement part is evaluated as a Perl expression. `sprintf` is documented in sprintf: the first argument is the format specifier, in this case `%i`, aka `%d`: "a signed integer, in decimal", where `2.2` specifies a minimum width of 2 and a precision of 2 (personally, I would have written it as `%02d`, TIMTOWTDI). As for the argument to be formatted, `$1` refers to the first capture group of the regex, in this case the two digits of the hour, from which 1 hour is subtracted. The formatted string returned by sprintf is then used as the substitution. Hope this helps, -- Hauke D	[reply] [d/l] [select]
Re^6: Date/Time Manipulation by RobertJ (Acolyte) on May 25, 2016 at 19:22 UTC
Didn't notice the space (it is an actual character). The rest I was able to figure out from O'Reilley and a little Googling. Thanks for reminding me that " " is a character.	[reply]