The good news is: you do not need sed for this at all. In fact, as long as you are not manipulating a data stream you usually should not use it at all and use "variable expansion" instead. It is the shells equivalent of substr(), trim(), strtok() and similar functions found in other high-level-languages.

The first thing you want to do is to cut off the extension ".csv" from the filename:

Code:

file="JAN_DAT_TES1_201807181400.csv"
echo "${file%.csv}"

This works the following way: ${variable%pattern} cuts off the pattern from the end of the variables content if it is found. "pattern" is everything you could use as a filename pattern in the shell: "*" would mean any number of any characters (like in "file*"), "?" means any one character, etc. Notice also that this only DISPLAYS the resulting string, it does NOT CHANGE the content of the variable! If you want to change it lastingly you need to assign the new value:

Code:

file="${file%.csv}"

Since you want to cut off the last two zeroes either we can do that in a single run:

Code:

file="JAN_DAT_TES1_201807181400.csv"
echo "${file%00.csv}"

The next thing we want is the date to be cut off but we need to preserve it, so we assign a new variable with a copy of "$file"s contents, but with everything up to the last underscore removed. For this there is another expansion which works like the one i showed you but it cuts off from the beginning instead of the end:

Code:

file="JAN_DAT_TES1_2018071814"
echo "${file##*_}"

Notice that i used "##" instead of "#". "##" and its companion "%%" cut off the longest possible match whereas "#" and "%" cut off the shortest possible match. That means:

Code:

file="JAN_DAT_TES1_2018071814"
echo "${file#*_}"     # gives "DAT_TES1_2018071814"
echo "${file##*_}"    # gives "2018071814"

Now, putting it all together (notice that you can use a variable as pattern too!):

Code:

for file in /some/where/*csv ; do
     file="${file%00.csv}"
     date="${file##*_}"
     file="${file%_${date}}"
     echo "my file is: $file , my date is: $date"
done

I hope this helps.

bakunin