Script bash

[antonellocaroli]

I'm trying to make some bash scripts to perform some operations with beets.

But with this I can't find a way to make it work and I don't really understand why, if anyone has any more knowledge....

This is the script, just a test to see how it works:

#!/bin/bash

set -e

repeats=1
clear=false


while (( $# >= 1 ))
do
    key="$1"

    case $key in
        -a)
            genre="$2"
            shift # past argument
            ;;
        -c)
            exgenre="$2"
            shift # past argument
            ;;
         *)
            # unknown option
            ;;
    esac
    shift # past argument or value
done




if [ ${#exgenre} -eq 0 ]; then
  exgenre=
else
  exgenre="^genre:$(echo \"$exgenre | sed 's/,/\" \^genre:\"/g' | sed 's/$/"/')"
fi

echo "variable:"
echo $exgenre
echo

#beet test
echo "command with variable:"
beet ls -f '$path' genre:"$genre" $exgenre | wc -l
echo
echo "command normal:"
beet ls -f '$path' genre:Jazz ^genre:"Art Rock" ^genre:"Rock" | wc -l

Running the script in this way should give me the same result for the two 'beets' commands, instead it gives two different results, and I don't really understand why...

./test.sh -a Jazz -c "Art Rock","Rock"

this is the result:

variable:
^genre:"Art Rock" ^genre:"Rock"

command with variable:
20

command normal:
17339

they should both be 17339

I do not understand how the variable is interpreted by beets

[sampsyo]

"Splicing" shell commands using shell variables like this is notoriously difficult! Especially when the arguments you're trying to expand include shell-escape characters like ". You would like the value of $exgenre, which is ^genre:"Art Rock" ^genre:"Rock", to be passed as two arguments to beets. However, the shell doesn't split up strings like that when they come from variables: it's split only on whitespace, as controlled by the IFS variable. So it will pass three arguments to beets.

You can see this behavior even without beets, as in this small shell script:

#!/bin/sh

exgenre='^genre:"Art Rock" ^genre:"Rock"'

sh -c 'echo $#' -- $exgenre
sh -c 'echo $#' -- ^genre:"Art Rock" ^genre:"Rock"

sh -c 'echo $#' is a way to count the arguments. This prints 3 and then 2, indicating that the argument grouping is different for the two commands.

Anyway, shell scripting is painful, and I think the best solutions here either escaping with printf or using bash's arrays. Or give up on shell scripting altogether, in favor of something like zx…

[stale[bot]]

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