trouble piping grep into select--best solution?

[jamesisin]

I am writing a script to sync playlists onto a music device.

I have some code which will give me a list of user-generated playlists:


PLAYLISTS=$( grep playlist\ name.*type=\"static\" $RHYTHMBOXLISTS | awk -F '"' '{ print i$2 }' )

The variable $RHYTHMBOXLISTS is the location of the playlists file:


RHYTHMBOXLISTS="/home/$USER/.gnome2/rhythmbox/playlists.xml"

Running the code under PLAYLISTS (ie, that which resides in the parentheses) returns a list of the names of the playlists which the user has created using Rhythmbox.


grep playlist\ name.*type=\"static\" /home/username/.gnome2/rhythmbox/playlists.xml | awk -F '"' '{ print i$2 }'
_0_0_Burn_0_0_
_0_0_RockBox1
_0_0_RockBox2
_0_j2 [16]
_1_2_BeattlesCovers
...

I would like to put selectable numbers before each playlist. I tried using select:


select SYNKLIST in "$PLAYLISTS"; do

echo "You chose "$SYNKLIST", processing..."

done

The problem is that the list gets transformed somewhere. As written above I get a one item list which gives the entire list (with line breaks, but all one item). If I remove the quotes around $PLAYLISTS I get a list of each space separated word (no longer broken at the line breaks in the grep list):


./RockBoxSynk.sh
...
1) _0_0_Burn_0_0_
_0_0_RockBox1
_0_0_RockBox2
_0_j2 [16]
_1_2_BeattlesCovers

or

./RockBoxSynk.sh
...
1) _0_0_Burn_0_0_ 51) Slow
2) _0_0_RockBox1 52) Fire
3) _0_0_RockBox2 53) [16]
4) _0_j2 54) Digital
5) [16] 55) Dawn
6) _1_2_BeattlesCovers 56) [13]


Am I going about this all wrong? What is the best solution?

I would like the user to be able to select one or more playlist from the list (with options to QUIT and select ALL).

[falconindy]

You probably want to wrap the results into an array. You'll need some tricky to avoid having issues with spaces:


SAVEIF=$IFS
IFS=$'\n'
PLAYLISTS=($( grep playlist\ name.*type=\"static\" $RHYTHMBOXLISTS | awk -F '"' '{ print i$2 }' ))

for list in "${PLAYLISTS[@]}"; do
# good stuff goes here
done

[jamesisin]

Thanks for stopping by to help out.

Perhaps I'm still a little confused. I built this to test your suggestion:


RHYTHMBOXLISTS="/home/$USER/.gnome2/rhythmbox/playlists.xml"

SAVEIF=$IFS
IFS=$'\n'
PLAYLISTS=($( grep playlist\ name.*type=\"static\" $RHYTHMBOXLISTS | awk -F '"' '{ print i$2 }' ))

for list in "${PLAYLISTS[@]}"; do
# good stuff goes here

read -p "Please select PlayLists to synk: "

done

No list appears.

Does it matter that the parsing of the IFS comes before the grep pipeline?

What does the second parenthetical pair in PLAYLISTS do?

What does the enclosed snail [@] in the for loop do?

[falconindy]

Ah. Got it. Assumed you were a little more familiar with Bash. Consider the following:


var=zero one "two alsotwo" three four
On it's own, you have no way to separate out these elements except to iterate over them with a construct like a for loop. You'll also run into issues with the 3rd element because the quotes won't be preserved in a meaningful way.

Fear not, Bash gives you arrays!

var=(zero one "two alsatwo" three four)
Now we can access each element directly by its index. Better yet, quoted elements are preserved.

$ echo ${var[0]}
zero
$ echo ${var[2]}
two alsotwo


If you want to iterate over the contents, you have two options:

$ echo "${var }"
zero one two alsotwo three four
$ echo "${var[@]}"
zero one two alsotwo three four
They look exactly the same, but in practice, will behave slightly differently. Whereas using the * operator with the array name quoted will return the entire content of the array as a single quoted variable, the @ operator with the array name quoted will return each element quoted for you.


$ for ele in "${var }"; do
> echo $ele
>done
one two also two three four

$ for ele in "${var[@]}"; do
> echo $ele
>done
one
two also two
three
four

9 times out of 10, you'll want to use the quoted @ syntax.

[jamesisin]

My system is behaving a little differently:


$ var=(zero one "two alsatwo" three four)
$ for ele in "${var[@]}"; do echo ele; done
ele
ele
ele
ele
ele
$ echo ${var[0]}
zero


Huh? It's parsing the correct number of elements, but then it lists the variable name when called out with the snail.

(If I substitute that syntax into my select loop from the opening it does parse the elements as expected, so I think I can beat my selection section into submission. Thanks for the education. I'm just a BASH novice with good books.)

[falconindy]

My system is behaving a little differently:


$ var=(zero one "two alsatwo" three four)
$ for ele in "${var[@]}"; do echo $ele; done
ele
ele
ele
ele
ele
$ echo ${var[0]}
zero


Huh? It's parsing the correct number of elements, but then it lists the variable name when called out with the snail.

(If I substitute that syntax into my select loop from the opening it does parse the elements as expected, so I think I can beat my selection section into submission. Thanks for the education. I'm just a BASH novice with good books.)
Working as intended. You missed a $ sign that I've inserted into your code in bold.

edit: oh, looks like i did too.

[jamesisin]

Yeah, little missing characters are so easily overlooked. Funny that I got it correct in my script but not in my test.

Ok, I'm going back to digging. Now that I have my list of playlists I need to get user input to pick which of the playlists are to be included in the synk. I hope to find a way to allow select to accept multiple numeric input (like 1 2 4 13).

I know how to get it to accept my two extra entries (ALL and QUIT) but I also should limit its numeric input to numbers within the range of the list grep/awk/sed generates.

Thanks again for your assistance.