Building a parser to use in script (bash)

Use date to format your string:

$ date +"%d/%m/%Y %H:%m aaa bbb ccc 123456 ddd 7890 eee"
09/10/2015 14:10 aaa bbb ccc 123456 ddd 7890 eee

if that's what you meant.

Alternatively use printf, for example:

printf "%s/%s/%s %s:%s aa bb cc" 2015 01 01 00 00

or create equivalent sprintf function:

sprintf() { local stdin; read -d '' -u 0 stdin; printf "$@" "$stdin"; }

If you want to read other way round, use read, e.g.:

while IFS=':/ ' read d m y h m _; do echo "$d $m $y $h $m"; done < data.txt 

For more examples, see: How do I split a string on a delimiter in Bash?

Could be an aplroach more complex than what you need. But you are going in the same way... so:

Have you ever heard about machine learning tecniques used to recognize images? They are actually using many different masks (in your case a string mask) that you will need to chose randomly and then correct stocasticaly upon analises. XOR the mask with the string and sum characters value to a int. You will get a number for each mask, and you will actually produce a hash that tells you the matching of the string to your masks. Comparing similar hashs (with int numbers close to each other) those will be similar strings.

This is a tip. You can go easier or deeper, depend on your requirements.

At the end I solved with perl and regex, I have defined my string masks $FOO $BAR $BAZ, and then I have compared my input string with them

if ($myinputstring =~ $FOO) { 
 statement 
} elseif($myinputstring =~ $BAR) {
 otherstatment
} elseif ($myinputstring =~ $BAZ) {
 someotherstatement
} else {
 print_to_unmatched_log
}

Thanks

at the end I have simplified my issue and I got back the bash solution. This is a fast pseudo, tell me what do you think about.

pre:
myregex1="^[0-9]{2}/[0-9]{2}/[0-9]{4}[[:space:]][0-9]{2}:[0-9]{2}$"
myregex2="^[[:space:]]\([0-9]{3}\)$"
myregex3="^[[:space:]][0-9]{8}$"
myregex4="^foo[[:space:]]bar$"
myregex5="^[[:space:]]baz\([0-9]{3}\)$"
...
nospace() { printf "$1" | sed -e 's/^[[:space:]]*//'; }



   the code:
    while loop each line of my source text file; do
    buffer="";i=0
    while IFS= read -r -N 1 char; do
    buffer+="$char"; let "i++"
    if [[ $buffer =~ $myregex1 ]]; then printf -v myvar1 "$(nospace "$buffer")"; i=$(( $i - ${#buffer} )); buffer="${buffer::-$i}" 
    elif [[ $buffer =~ $myregex2 ]]; then printf -v myvar2 SAME_STATEMENT_BEFORE
    elif SAME_STATEMENT_BEOFRE_WITH_MYVAR3
    elif ...
    fi
    done <<< "$mylinegotfromtextfile"
    done < $mytextfile

That's all, did you know a better solution?