From within a bash script, how do I create a new filename, place a $variable in part of it?

Question

Within a loop in my bash script, I am 'doing work', then writing the result of each iteration to its own file. I'd like to name these files

# User-defined Function (UDF)
processLine(){

line="$@" # get all args 
index=$(echo $line | gawk -F::: '{ print $1 }')
content=$(echo $line | gawk -F::: '{ print $2 }')

# Let's tr it to remove double-quotes(42) and lfs(12)!
content=$(echo $content | tr -d \012)
content=$(echo $content | tr -d \042)
content=$(echo $content | tr -d \054)

# - THEN APPEND THE LINE to OUTPUT FILE
echo $index','$content>>OUTPUT

# - ALSO, save 'raw' individual student data as a backup
echo $content>STUDENTS/STUDENT.$index
}

Yes, I know, that tr stuff is poorly written! Hey, it's almost my first script!

I'd like to write filenames like STUDENT.7534, not STUDENT."7534" - which can't even be opened.

Hmmm... What to do?

Answer 1

Critique:

# User-defined Function (UDF)
processLine(){

    index=$1  # First argument is the index
    shift     # Remove the index
    # Grab the content - "$*" is fine here,
    # and $* or $@ without quotes would probably work
    # And do the editing in a single tr operation
    # And document what we're doing completely
    # Let's tr it to remove double-quotes (42) and lfs (12) and comma (54)!
    content=$(echo "$*" | tr -d \012\042\054)

    # - THEN APPEND THE LINE to OUTPUT FILE
    # Single quotes around the comma are unnecessary
    echo $index,$content >>OUTPUT

    # - ALSO, save 'raw' individual student data as a backup
    echo $content >STUDENTS/STUDENT.$index
}

There is nothing in this which adds (or removes) double quotes in the index - so the call to this code must be putting the quotes there.

You say the output file name is:

STUDENT."7534" - which can't even be opened.

It can be opened as long as you remember that the shell removes double quotes, so you have to stop it doing so:

cat 'STUDENT."7534"'

All you have to do is persuade your instructors that it is a security precaution to ensure they know enough shell to be able to access your protected files.