LinuxQuestions.org - Bash indirect reference to array variable(s)

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Bash indirect reference to array variable(s)

I'm trying to programmatically create and reference arrays which
are based on the files in a directory. The arrays are created using
a 'for' loop, that's not a problem. The difficulty arises in referencing each array after creation. I tried creating a separate file which contains the file names, then accessing each array by filename (either directly or indirectly), but niether is working.

Consider:

Code:

for fname in *

do

    fnamearray[$index]=$fname

    stat -c %n,%U,%x,%y $fname > $TEMPFILE

    fnamen=$(awk -F"," '{ print $1 }' $TEMPFILE)      # File name

    fnameu=$(awk -F"," '{ print $2 }' $TEMPFILE)      # User name

    fname=$(awk -F"," '{ print $3 }' $TEMPFILE)        # Access time

    fname[3]=$(awk -F"," '{ print $4 }' $TEMPFILE)    # Modification time

    let 'index+=1'

    echo ${fnamearray[$index]} >> $TEMPFILE2

done



echo ${fnamearray[0]}                                  # 1st file name

echo $(!fnamearray[1])                                  # Should be element 1 (user name)?

Maybe what I'm trying to do is not yet implemented in Bash? If not,
what is the proper syntax/construction to dereference an array variable indirectly?

you may find this idiom a bit cleaner rather than all that
awk tempfile nonsense.
(I am using date, as no 'stat' on solaris)

you can use set to extrapolate to the numbered parameters

Code:

$ date

Wednesday October 18 14:57:28 BST 2006





$ set -- $(date)

$ echo $*

Wednesday October 18 14:57:39 BST 2006



# let's reverse it!

$ echo $6 $5 $4 $3 $2 $1

2006 BST 14:57:39 18 October Wednesday

what is "!" for

echo $(!fnamearray[1]) # Should be element 1 (user name)?

THANK YOU! Yes, the awk/TEMPFILE is ugly and unnecessary, but it was my first try at the script and I was stuck. I always have the feeling that the more ugly and unwieldy the code I'm writing is, the more likely there's a much easier way to do it. Thanks again! :-D

very very true.
uglyness is KEY.

If my code starts getting ugly, or complicated I seriously
think about re-doing it.

It's a cool technique the set, very few people know of it.
remember that set technique will clobber your existing parameters
unless you put in a function or a subshell,

try this to show your PATH:

Code:



(IFS=:;set -- $PATH;for x;do echo $x;done)

ygloo, the "!" notation in that context is an attempt to indirectly reference a variable via the contents of another variable. I solved the problem by abandoning the indirect variable stuff and just assigning a unique variable for each file name called "$fname.stat" in the "for" loop.

I made some minor corrections to your original script:

Code:

TEMPFILE=tempfile

TEMPFILE2=tempfile2

for fname in *

do

    fnamearray[$index]=$fname

    stat -c %n,%U,%x,%y "$fname" > $TEMPFILE

    fnamen=$(awk -F"," '{ print $1 }' $TEMPFILE)      # File name

    fnameu=$(awk -F"," '{ print $2 }' $TEMPFILE)      # User name

    fname=$(awk -F"," '{ print $3 }' $TEMPFILE)        # Access time

    fname[3]=$(awk -F"," '{ print $4 }' $TEMPFILE)    # Modification time

    let 'index+=1'

    echo ${fnamearray[$index]} >> $TEMPFILE2

done



echo ${fnamearray[0]}                                  # 1st file name

echo "${!fnamearray[1]}"                                # Should be element 1 (user name)?

But I don't understand what you are trying to to in the last line. Suppose that ${fnamearray[1] is "poodle.jpg".
The indirection will expand to "echo ${poodle.jpg}".

----

To create an array of the files in the current directory you could do something like this:

Code:

fnamearray=($(find ./ -maxdepth 1 -type f -printf "%f "))