pulling lines related to the date

Question

I've got a text-file that's sorted by the first field, which is month/day (eg: 02-20)

I've been using grep on rhe text file, but that's easiest to do with today's date, using the date command in a script.

I'd like to pull up the prior 3 days, today's date, and the coming 5 days... but I don't know an easy way to handle the end of the month/into the next month. I could, I s'pose, hard code that in? But I was looking for an elegant solution to the problem, so I'm seeking suggestions.

I'd prefer to use regular commands so the script is as portable as possible.

ie: by portable, I mean not just limited to Linux/GNU machines (and/or having to install specific utilities in order to make everything run). Currently I think I'm on a BSD machine, and I've been on most flavors of UNIX (Solaris, blah, blah, blah) - and probably will be in the future.

I'd take something that's more convoluted to program/script, that uses very basic tools, over having to remember to install packages everytime I might be on a different flavor of UNIX (when I could just scp in my scripts directory and have it work).

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FYI: Current date -d flag sets daylight savings time :)

 -d dst  Set the system's value for Daylight Saving Time.

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Okay, I just gave an example (as asked) of the type on data in the file (it's much bigger, obvs), but I didn't give edge cases. Here's an edge case, ie: how do I handle the end of month period, without programming in a test for the end of the month, for each month (Or 4 types of month: 30, 31, 28 & 29).

01-01   Something To Do Here    Notes that may run for a really long time
02-05   On the 5th of the Month         Do this other thing, because of X
02-06   The day after           Do this cleanup stuff
03-15   The Ides                Remember, remember the Brutus of December
03-29   Edge                    Does this show up on the 1st of April?
03-30   Edge2                   Does this show up on the 1st and 2nd?
03-31   Last day in the month   Shows?
04-01   Edge                    Does this show on 31st?  Or does it only show 03-35?

Answer 1

GNU date allows you to give strings to the -d option like -2 days and 5 days. The -f option allows these strings to be read from a file or pipe. So using GNU date and bash:

printf '%d days\n' {-2..5} | date -f - +%m-%d | grep -f - in_file

Update

If tcl is acceptable, here is a script to print out the dates:

#!/usr/bin/tclsh

set now [clock seconds]

for {set n -2} {$n<=5} {incr n} {
  set out_date [clock add $now $n days]
  puts [clock format $out_date -format %m-%d]
}

Just pipe the output of this to grep -f - as above.

Answer 2

Well here is a one liner that seems to do the job...

dt=$(date +%m-%d);for i in {-2..5}; do grep "$(echo "$dt"|awk -F"-" -v count=$i '{print $1"-0"$2+count}')" mtest; done

You can make this a function by adding this to your .bashrc ...

todolist(){  dt=$(date +%m-%d);for i in {-2..5}; do grep "$(echo "$dt"|awk -F"-" -v count=$i '{print $1"-0"$2+count}')" $1; done; }

and then you just call it

todolist whateverthefilename.txt

It isn't very pretty but I tested it with your data it did work.

$ echo -e "01-01   Something To Do Here    Notes that may run for a really long time\n02-05   On the 5th of the Month         Do this other thing,\nbecause of X\n02-06   The day after           Do this cleanup stuff\n03-15   The Ides                Remember, remember the Brutus of December">> mtest

$ dt=02-05; for i in {-2..5}; do grep "$(echo "$dt"|awk -F"-" -v count=$i '{print $1"-0"$2+count}')" mtest; done
02-05   On the 5th of the Month         Do this other thing,
02-06   The day after           Do this cleanup stuff

Answer 3

You can use touch to POSIXLY test the validity of a date string.

I'll use a couple options here.

• -c
  • Do not create a specified file if it does not exist. Do not write any diagnostic messages concerning this condition.

• -t

  • Use the specified time instead of the current time. The option-argument shall be a decimal number of the form:

    [[CC]YY]MMDDhhmm[.SS]
    

  • If the time cannot be represented as the file's timestamp, touch shall exit immediately with an error status.

  • Note that the [[CC]YY] fields are optional.

And so, for example:

testtime()
        if      command -v touch >&2
        then    touch -c ''
                eval '  touch -ct"$1" ""
                        [ "$?" = '"$? ]"
        else    { touch; } 2>&3
        fi      3>&2 2>/dev/null

It's pretty careful to handle matters portably, I think. In tests with both a GNU and an heirloom (Solaris) touch, the GNU tool returns 1 for a bad date and 0 for a good one, but the heirloom version returns 2 and 1 respectively. I'm fairly sure that the old Solaris tool's behavior is specifically referenced in the spec's rationale where I find:

• At least one historical implementation of touch incremented the exit code if -c was specified and the file did not exist. This volume of POSIX.1-2008 requires exit status zero if no errors occur.

I am more convinced when I compare the behavior of different versions of my heirloom tools. The one from the base set - which is designed to behave as much like the original set as is possible and still be useful on modern systems - is the one that returns the 2 and 1 as mentioned. However, when I use the /usr/heirloom/bin/posix2001/touch executable - which is the version which has been modified for standards compliance as necessary - it returns exactly as does the GNU tool.

In any case, the function handles both the old Solaris, the modified-for-compliance Solaris, and the GNU behaviors, because it compares the results of an intial call to touch on a ''null file operand (which definitely does not exist) against a second call on same and returns 0 for a good date or 1 for a bad one. It returns 127 and writes to stderr if touch cannot be found.

Here's how you can use it:

testtime MMDD0000 && echo good date || echo bad date

...where MM and DD are 2-digit decimal strings representing the date you wish to test. You can also check for valid times that way - and even with a .S seconds field.

Answer 4

I posted my first answer yesterday with way too little sleep. I am back and ready to try again. Rather than try to awk the dates I decided I was being too clever so I went back and rethought it.

todolist(){ for i in {-2..5}; do grep "$(date -d "${date} +$i days" +%m-%d)" $1 ; done; };

Just add the one-liner to your .bashrc and then feed it the file.

This time I let date do all the work. I got the hint from here. This little bit will add any number of days from today's date and output it in the format you need for your file...

date -d "${date} +$i days" +%m-%d)"

The function above should now work without resorting to hard-coded values.