How to change a file name containing ":" in timing info

To loop over all files in the current directory that contain at least one : character in their name and ends with .txt, and to change the : characters to _, with the ksh93, zsh, bash, mksh shells (or recent versions of busybox sh), you may use

for name in ./*:*.txt; do
    newname=${name//:/_}
    mv -i "$name" "$newname"
done

or, shorter,

for name in ./*:*.txt; do
    mv -i "$name" "${name//:/_}"
done

The parameter substitution ${name//:/_} would change all : to _ anywhere in the value $name (a ksh93 operator also supported by the shells mentioned above).

The mv -i would rename the file, but would ask for confirmation if the new name is already taken.

The filename that you show as an example would be changed to ee_Sun_Aug_11_22_20_27_GMT-8_2019.txt.

Your command

cp /var/log/ee.txt ee_`date`.txt

does not work because date outputs a string with spaces in it. The spaces would have made cp think you wanted to copy several files into a directory. Hence the "is not a directory" error.

The following would have worked better:

cp /var/log/ee.txt "ee_$(date).txt"

It works better, not because I changed your backticks to $(...) but because I double-quoted the new name.

This would have created the file ee_Sun Aug 11 16:57:37 CEST 2019.txt (or something similar).

To get a neater looking filename, you may want to specify the output format for date a bit more precisely:

cp ee.txt "ee_$(date +"%F_%H-%M-%S").txt"

The format string %F_%H-%M-%S would be described in the strftime(3) manual on your system (man 3 strftime), or in the manual for the date command, and you would end up with a filename like ee_2019-08-11_16-59-55.txt. If your date doesn't support the %F directive, you can replace with %Y-%m-%d.

Alternatively,

cp ee.txt "$(date +"ee_%F_%H-%M-%S.txt")"

(letting the date command format do most of the work in creating the new filename)