Question

Preamble:
So I have a project whereby I need to run a conversion tool on a bunch of files. There are multiple steps to the conversion, and it can take a while. Since these files aren’t necessarily in the same directory, I created a text file with the filenames to convert:

<filenames.txt>

/home/me/Documents/file1.txt
/home/me/Documents/file2.txt
/home/me/Documents/file3.txt

Problem:
I then have a bash script to run over these files, and do the conversion steps. However, I try and echo the phase and filename, and echo, in this case, sticks the echo’d text in the middle of the filename:

<script.sh>

cat filenames.txt | while read some_file
do
    echo
    echo "Begin FORMAT_A to FORMAT_B conversion..."
    echo "FORMAT_A Filename:"
    echo $some_file
    formatb_dir= dirname $some_file | tr '\n' "/"
    formatb_file= basename $some_file ".xml" | tr '\n' "_"
    formatb=$formatb_dir$formatb_file"form_b.xml\n"

    echo "FORMAT_B Filename:"
    echo $formatb
done

Produces output like this:

Begin FORMAT_A to FORMAT_B conversion...
FORMAT_A Filename:
/home/me/Documents/file1.txt
/home/me/Documents/file1.txt_FORMAT_B Filename:
form_b.xml


Begin FORMAT_A to FORMAT_B conversion...
FORMAT_A Filename:
/home/me/Documents/file2.txt
/home/me/Documents/file2.txt_FORMAT_B Filename:
form_b.xml


Begin FORMAT_A to FORMAT_B conversion...
FORMAT_A Filename:
/home/me/Documents/file3.txt
/home/me/Documents/file3.txt_FORMAT_B Filename:
form_b.xml

“FORMAT_B Filename”, the echo’d text, has appeared before the appended text “form_b.xml”.

I looked at the man pages for dirname, basename, echo and tr, but I didn’t spot anything that looks like it’d cause what I’m seeing. I tried looking around on Google, but I’m not sure I’m asking the right questions (“bash echo text before variable”?).

Question: Why is my echo putting the echo’d text in the middle of my variable?

(possible related question: “Am I going about what I’m doing in completely the wrong way?”)

Edit: I accepted fortea’s answer because it walked me through what I didn’t understand about variables and getting the output from commands. That said, dogbane and Jonathan Leffler showed better ways of doing what I was doing.

Answer 1

The problem is in the declaration of variables:

formatb_dir= dirname $some_file | tr '\n' "/"
formatb_file= basename $some_file ".xml" | tr '\n' "_"
formatb=$formatb_dir$formatb_file"form_b.xml\n"

Try a new line: echo $formatb_dir: it does not contain anything because after the ‘=’ there is a blank space. Then bash reads dirname $somefile |tr '\n' "/" and it executes this command. The same when you create formatb_file, but this time the command is basename. (this is what appears before “FORMAT_B Filename:”).
Then formatb is created correctly, but $formatb_dir and $formatb_file are empty, so $formatb will contain only "form_b.xml\n".
Then you echo “FORMAT_B Filename:”.
Then you echo $formatb, which will output “form_b.xml”.

So, you should use something like this:

formatb_dir=$(dirname $some_file | tr '\n' "/")
formatb_file=$(basename $some_file ".xml" | tr '\n' "_")
formatb=$formatb_dir$formatb_file"form_b.xml\n"

Read here