Adding ";" (semi-colon) in each space between hour and filename

Since there are no other space characters in your list, you can use sed to replace the first space character in each line with a semicolon:

sed 's/ /;/' file

This can be done with awk or sed:

awk '{print $1";"$2}' file

awk -F ' ' '{print $1,$2}' OFS=";" file

sed 's| |;|' file

The first awk command prints a ; between the first and second column and the second converts the space delimiter to a ;. The sed command simply replaces the space with a ;. To edit the file in place with sed:

sed -i 's| |;|' file

With awk, assuming that the version is 4.1.0 or later:

awk -i inplace '{print $1";"$2}' file

awk -i inplace -F ' ' '{print $1,$2}' OFS=";" filename

Had similar problem at an email server, just put this list in a file01.txt text file, then apply following command:

cat file01.txt | sed 's/[ \t]/;/g' > file02.txt