Compare date values between two files

Question

I have two files with dates:

File1

12/22/2017

File2

12/21/2017    
12/20/2017    
12/23/2017    

File1 will only have one record. File2 will have multiple records. I need to check if any of the dates in file2 is greater than the date in file1. Date Format in both files will be MM/DD/YYYY.

Answer 1

Here is small script which sorts both files, greps for later dates than file1, and then counts (wc -l) if there are more than 1 uniq line (should be only 1 which comes from file1):

if [[ "$(sort -t/ -k3,3n -k1,1n -k2,2n file1 file2 | grep -A 1 -f file1 | uniq | wc -l)" -gt 1 ]]
    then
       echo "Date in file2 is greater than file1"
    else
       echo "Date in file2 is not greater than file1"
fi

Answer 2

GNU awk solution:

awk -F'/' '{ d=$3$1$2 }
           NR==FNR{ t=d; nextfile }
           d > t{ 
               print "file2 has date(s) greater than in file1";
               exit 
           }' file1 file2

The output:

file2 has date(s) greater than in file1

Answer 3

Get the time in seconds from epoch (see man stat) and print the difference.

T1=$(stat --printf='%Y\n' file1.txt)
T2=$(stat --printf='%Y\n' file2.txt)

echo $(($T1 - $T2))