View Full Version : [SOLVED] Bash Variable from Data Question

December 4th, 2008, 11:12 PM

I'm creating a shell script that will be taking in data and I want to create separate variables that contain the name of the data taken in.

for instance, if the data obtained is in a variable called $var1 = "txt", I want to create a new variable named "txt_count" somehow using $var1. I am also wondering if I can later test these variables in an if statement, using the same kind of concept.

Something along the lines of $var1_count.

I can't just use an if statement, as I am dealing with a lot of data that I want to do this for.

For instance, in the vain of filenames, if I had txt, jpg, ogg, cpp, I'd want to create corresponding variables txt_count, jpg_count, ogg_count, and cpp_count [except that I am doing this with over 100 pieces of data]. And then later, I want to be able to say, based on having only this $var1 [which could be equal to txt, jpg, ogg, or cpp], and say does $var1_count exist in an if statement or something along those lines.

I'm not sure if this is possible in bash.

December 4th, 2008, 11:29 PM
note, something like this:

echo $var_count


0_count=2: command not found

I suppose an easier problem to tackle would be can I create variables like this?

If I have a file containing:


And I read those [individually] off of the file into a variable called $ftype, could I then make a new variable which is the basically equal to the value of $ftype. Basically, it's like psuedo-dynamically creating variables. Is that possible?

December 4th, 2008, 11:59 PM
Possible, yes, but you really should avoid such programming. Instead, you could use arrays for example. Here's a small bash script checking all files in the current directory, counting the number of files with the same extensions:


# Declare $extensions and $counts to be arrays. Not really necessary, but it
# shows that you intend these to be arrays.
declare -a extensions
declare -a counts

for file in *.*; do
# Set $ext to $file with everything up to the last '.' removed.

# Check if $extensions has this extension already and increment the count
# for that extension if that is the case
for ((i=0; i < ${#extensions }; i++)); do
if [ "$ext" = "${extensions[i]}" ]; then
# If $i equals the size of the array, there wasn't an entry for that
# extension already, so we add a new element to the arrays.
if [ $i -eq ${#extensions } ]; then

# Print the results
for ((i=0; i < ${#extensions }; i++)); do
echo "There are ${counts[i]} files with '${extensions[i]}' extension"

To do what you originally wanted, you'd need to use eval

$ var=txt
$ eval ${var}_count=2
$ echo $txt_count

December 5th, 2008, 03:17 PM
Yes, I was thinking about using arrays. Thanks for both tips! =)