BASH fancy test vs if statements how to?
 

I cannot figure out what search words to get this off of google. So I am coming here to seek my answer(s).

I am wanting to see if I can get this to run faster then it already is by shorting up the code for bash to preform checks before issuing the commands.

This is the current way this code block is written. I do not really need it to check to see if the first two varitables are empty or not. Because I already ensured they are not with puddletag.

With this BASH syntext
As I figured one cannot add an else to this from of writting test because it lacks the if then
Writting it this way


gets me these results
It already moves the file reguardless if the test to see if the directroy is not there so then it gets to the is the directroy there and goes to move it it cannot be found because it already movied it. making the first test if not there then create it obsolete. It needs to be created once for the first file then the rest get moved into it after words, But not putting faith in this BASH I run a test to be sure it is there before telling it to move the file to same directory.

I hope I explaned that logic ok.

even when I chance it. getting rid of all of the echo and making it just one liners

I get this
as it moved that file already when it goes to check that next test of course the directory is already in place and tries to move a file that has alredy been moved.

SO I am thinking well I got to use the old if then else to get this, or is their a better logical way of doing this so that it will just run faster that I have not thought of yet to do this out there in someone elses head?

I guess I could do it like this: But I was looking to beaf up my BASH with using [[ check for true ]] && do something(s)


Does anyone have a link to the documentataion on that from of writting BASH to share?

[[ if test true ]] && do something(s)

in short you need { } if you want more commands after &&, otherwise condition will only be valid for the first one

So it does use brackets. I dismissed that idea before trying it. Because it is BASH and not C or similar. Thanks.

But that leaves an else do something "esle" out of the picture.

Suppose I'll see if I can blow something up.

doesn't work
error
OK

I think I almost got it, I am still getting one error on the first creation of a Directory due to the next line

error
I want to eliminte having to check it if is already there because the first block of code made sure it is while keeping it down to the lest amount of lines of code as possible.

what was that one liner that C has? Something like this (its been a while)
I think that is how it went.

OK I think I found it.


BASH Ternary Operators

No, you cannot use "else" without "if ... then", but you can accomplish it this way:The catch (familiar to Python programmers) is that you hve to ensure that code block 1 always ends with a "true" condition (zero return code). You can do that by making the last command in code block 1 one that always succeeds, like "true" or ":".

Doing that should be an intellectual exercise only. In the real world, "if ... then ... else ... fi" would be preferable.

NOT WORKING YET

using this example
mine is
I get this error
This does not work either I am getting the same error. done unexpected.

I would like to step back a little from what is perhaps the actual problem.

1. mkdir -p will already perform its own test if the path exists and create if not or skip, so I am not seeing the point of the test??

2. Testing (or using above) on both $move_to and "$move_to"/"$ARTIST"/"$ALBUM" is again a waste as it will make all required parent directories as needed, or again, skip if they all exist

3. This one is personal, but you only need one set of quotes, eg.
4. I am also not a fan of mixing my arithmetic operations, so either use (()) or expr, eg.
5. I would also use above for the while loop test

6. Remember that when piping into a while loop, you will not be able to use any of the variable values outside the loop due to be in a subshell. The alternative would be:
Hope some of that helps. It may also resolve the actual issue you are having ... maybe

That closing curly brace is only recognized when it's at the start of a command. You need a semicolon after the command that precedes it:

I am starting to figure that out. Too it seems that the Ternary Operator (?:) while it does work in BASH if used with two brackets ((?:)) it can only be used with non-strings comparisons.

Regardless, I am not getting it to work. lol

But according to this

Ternary operator in bash

Their is a way to fake it.
In here Ternary operator (?:) in Bash it shows many different ways to perform this task.
one example
But I am not having any success. With any of these one liners. When I place it in a one liner I keep getting an error
within my while loop

The only one I am getting to work is this one.
So I do suppose I'll mark this solved unless someone can give me a one liner that will work within a while loop.

Cheers and thanks!

btw
looking at your code example again after I posted this. I see a difference from what I tried. so I'll give that a try.

OK I did it! yeah!! woo hoo! :D
I needed one more ; within that first pair of { } at the end to get rid of the unexpected done error along with what you did placing a semi-colon at the end of the second command. ;

@pan64
@rknichols

+1 given thanks!
and to
@grail
for the tips in coding BASH

Just to conclude, the simplest one liner is:
The mkdir will always be true whether it creates the path or not :)

I actually didn't know that. Thanks for pointing that out. I only used it to do directory/subdirectory. Habit to check before jumping mode removed.

yeah I knew it was redundant, but I left it there anyways.


Done. Good recommendation.

Changed it to the later.
Thanks, I've been not liking doing it that way for some time now. Changed.


My Code it now way shorter than the one liner I just posted got me to mark solved. I went back over this post that is when I noticed yours within it. Gave it a look see took your advice and this is what I ended up with.

No more test before issuing commands.

Thanks again!

No probs ... here are some twists I had on your code:
The typset and let are again a personal preference but up to you :)

Take what you like :D

Just to check out everything you did for a look see. I get an error.. what? yep an error
It is showing green in greny color code for bash script.
the error
Not that I understand what it going on with but that is why I set -x
the EOF is doing what?

you got links to BASH pages that I could look over to educate myself on this?


commenting it out the cat <<-EOF -- to --- EOF - , it runs fine and I see what that set is doing thanks.

Changed the echo count to this
I diffidently see a speed up between files.

For the <<-EOF explanation:

http://man.cx/bash

Under the "Here Documents" section.

And for the set -- explanation:

http://man.cx/set

Search for -- in the page for information.