bash function to write comments to a newly created file

Question

Please see the following function —

function touchm(){
    date=$(date +'%Y-%m-%d %H:%M:%S')
    read Y M D h m s <<< ${date//[-: ]/ }
    file_name=$1

    if [[ $file_name =~ ^[0-9a-zA-Z+_-]+.[py|pl|rb|sh] ]]; then
        echo "#
# $file_name
#
# Created by $MASTER on $M/$D/$Y at $h:$m:$s
# Copyright (c) $Y $MASTER. All rights reserved.
#
" > $1

    elif [[ $file_name =~ ^[0-9a-zA-Z+_-]+.[m|h|c|cpp|] ]]; then
        echo "//
// $file_name
//
// Created by $MASTER on $M/$D/$Y at $h:$m:$s
// Copyright (c) $Y $MASTER. All rights reserved.
//
" > $1

    elif [[ $file_name =~ ^[0-9a-zA-Z+_-]+.[ml] ]]; then
        echo "(* *)
(* $file_name *)
(* *)
(* Created by $MASTER on $M/$D/$Y at $h:$m:$s *)
(* Copyright (c) $Y $MASTER. All rights reserved. *)
(* *)
" > $1

    else
        echo "What bullshit. Give me a good file name"

    fi
}

so whenever I execute:

touchm 2-r_f.ml

this should generate an ml file with ml type comments. But it doesn't do that. It generates c type comments.

Moreover, I need to accommodate for + and _ (underscore) as well but currently it doesn't seem to work. Is that a bad regex? If so, can I get pointers to correct it?

Thank you

Answer 1

You can try using cat to do this instead, i.e.

cat << EOF > output-filename
# $file_name
#
# Created by $MASTER on $M/$D/$Y at $h:$m:$s
# Copyright (c) $Y $MASTER. All rights reserved.
#
EOF

If you want to indent the code above, change << for <<- which will remove leading tabs.

Also, yes, it is bad regex. character classes (square brackets) don't need pipes, that is for having alternative matches inside of round brackets. you want something like:
Replace: $file_name =~ ^[0-9|a-z|A-Z|-].[ml]
With: $file_name =~ ^[0-9a-zA-Z+_-].[ml]

You could also replace the * with a + to indicate 1 or more, as that regex would also match '.ml'. Make sure a hyphen is the last character in a character class, otherwise it will assume you are specifying a range.

EDIT: try this, just tested with a .sh, .cpp and .ml file. Out of curiosity, is the 3rd if statement supposed to be for .ml, or .m OR .l as you seemed to be matching? the second if statement also matched .m, so one of them is probably wrong, below code assumes the 3rd if should be .ml

function touchm(){
    date=$(date +'%Y-%m-%d %H:%M:%S')
    read Y M D h m s <<< ${date//[-: ]/ }
    file_name=$1

    if [[ $file_name =~ ^[0-9a-zA-Z+_-]+\.(py|pl|rb|sh)$ ]]; then
        echo "\#
# $file_name
#
# Created by $MASTER on $M/$D/$Y at $h:$m:$s
# Copyright (c) $Y $MASTER. All rights reserved.
#
" > $1

    elif [[ $file_name =~ ^[0-9a-zA-Z+_-]+\.(m|h|c|cpp)$ ]]; then
        echo "//
// $file_name
//
// Created by $MASTER on $M/$D/$Y at $h:$m:$s
// Copyright (c) $Y $MASTER. All rights reserved.
//
" > $1

    elif [[ $file_name =~ ^[0-9a-zA-Z+_-]+\.ml$ ]]; then
        echo "(* *)
(* $file_name *)
(* *)
(* Created by $MASTER on $M/$D/$Y at $h:$m:$s *)
(* Copyright (c) $Y $MASTER. All rights reserved. *)
(* *)
" > $1

    else
        echo "What bullshit. Give me a good file name"

    fi
}