Question

I have a normal…

for file in *
do
    #do something here
done

…Code.
The problem is that I want to sort the row of the files by a custom date, the date is defined in the second line of the files.
I got to problems here:

1.How do I find out what’s in the second line of these multiple files before I actually run

for file in * do

2.How do I sort the loop by this custom string then?

This doesn’t work but maybe it will help you understanding my problem:

for file in *
do
    customdate="$(sed -n 2p $file)"
done

for file in * sort by $customdate
do
    #do something here
done

Answer 1

I think you need two loops. The first list reads that date out of the files and builds an index. and the second loop goes through that index. You can use a delimiter to split the index out again to get the filename out of the index again.

index=""
for file in *
do
   customdate="$(head -2 $file | tail -1)"
   index="${index}${customdate},${file}\n"
done

for key in `echo -e ${index} | sort`
do
   customdate=${key/,.*/}
   file=${key/.*,/}
   # PROCESS FILE HERE
done