Reading an array from another file

nobody123 · 02-19-2009, 03:13 PM

Hello, I am very new to Linux so please bear with me. Onto the problem:

I have created an array in a file (let's call this file file1). I then create another file (file2) to run a few scripts. My question is:

How to you access the array created in file1 from file2?

Any help would be greatly appreciated. Thank you for your time.

PatrickNew · 02-19-2009, 03:27 PM

Okay, well to help you, we're going to need you to answer a few questions.

1. What programming language are you using?
2. What format are these arrays in?

nobody123 · 02-19-2009, 04:05 PM

Quote:

Originally Posted by PatrickNew

Okay, well to help you, we're going to need you to answer a few questions.

1. What programming language are you using?
2. What format are these arrays in?

Thank you for your quick response. To answer your questions, I am programming in BASH and the format of the arrays are as follows:
arrayname=(arrayelements)

PatrickNew · 02-19-2009, 04:09 PM

Okay, so we have the name, followed by the list in parentheses. Are these elements separated by commas, tabs, spaces?

In bash, most array handling is kinda ad-hoc. By that I mean that it depends a lot on what you want to do. Bash doesn't really have built in arrays. So do you want to iterate over each element and execute some command? Or do you want to add them up? Or something else?

nobody123 · 02-19-2009, 04:19 PM

Quote:

Originally Posted by PatrickNew

Okay, so we have the name, followed by the list in parentheses. Are these elements separated by commas, tabs, spaces?

In bash, most array handling is kinda ad-hoc. By that I mean that it depends a lot on what you want to do. Bash doesn't really have built in arrays. So do you want to iterate over each element and execute some command? Or do you want to add them up? Or something else?

The elements are indeed separated by spaces. What I want to do with the array is read the array elements and execute a command (e.g. using the 'grep' command to search for a specific value and display).

PatrickNew · 02-19-2009, 04:25 PM

Code:

for X in `sed name_of_the_file -r -e 's/.*\((.*)\)/\1/g' | tr -d ','`
do
   #Your command here, where $X is replaced with this entry in the array
done

This takes the file and the sed command strips off the name of the array and the parentheses. The output of that is then sent (because of the |) to tr -d ',' which pulls off all the commas, so that now you just have numbers separated by spaces.

the
for [variable name] in [series of values separated by spaces]
do
#stuff
done

is the bash for-each loop.

nobody123 · 02-19-2009, 04:44 PM

Quote:

Originally Posted by PatrickNew

Code:

for X in `sed name_of_the_file -r -e 's/.*\((.*)\)/\1/g' | tr -d ','`
do
   #Your command here, where $X is replaced with this entry in the array
done

This takes the file and the sed command strips off the name of the array and the parentheses. The output of that is then sent (because of the |) to tr -d ',' which pulls off all the commas, so that now you just have numbers separated by spaces.

the
for [variable name] in [series of values separated by spaces]
do
#stuff
done

is the bash for-each loop.

Thank you for your piece of code. There are a few questions I have about it though:

Is it really necessary to have commas in an array? I have not been using any. If not, it is necessary to have | tr -d ','?
"Where X is replaced with this entry in the array"...does that mean an array element is supposed to be in 'X'?

Here is how I have been creating my arrays as of late:

Code:

artist = ( “The Beatles” “Elvis Presley” “Bing Crosby” “Michael Jackson” “AC/DC” “ABBA” “Bee Gees” “Bob Marley” “Cliff Richard” “Led Zeppelin” )

And yes, I am trying to read string values from the array. I do hope this does not make anything problematic. Thank you again for helping me

PatrickNew · 02-19-2009, 04:59 PM

Haha, no that is my mistake. I forgot that you said they were separated by spaces, I thought they were separated by commas. So yes - if you leave out the spaces, you can also leave out the tr -d ','.

Now I didn't realize that the elements of the arrays have spaces within them. That breaks the for - loop because it will try to call on things like '"The', 'Beatles"', '"Elvis', 'Presley"' and so on. Hrm, we'll need a new approach.

I'll think about this, and get back.

PatrickNew · 02-19-2009, 05:00 PM

Do you put multiple arrays in one file? The whole problem gets much easier if the entries are one per line.

nobody123 · 02-19-2009, 05:00 PM

Quote:

Originally Posted by PatrickNew

Haha, no that is my mistake. I forgot that you said they were separated by spaces, I thought they were separated by commas. So yes - if you leave out the spaces, you can also leave out the tr -d ','.

Now I didn't realize that the elements of the arrays have spaces within them. That breaks the for - loop because it will try to call on things like '"The', 'Beatles"', '"Elvis', 'Presley"' and so on. Hrm, we'll need a new approach.

I'll think about this, and get back.

Thanks again for your help. Please take your time!

nobody123 · 02-19-2009, 05:16 PM

Quote:

Originally Posted by PatrickNew

Do you put multiple arrays in one file? The whole problem gets much easier if the entries are one per line.

Yes, I do put multiple arrays in one file. I do believe I have been putting the arrays one per line (I do have more than one array. Here they are if you are interested in addition to the previous array stated:

Code:

CDName=( “Please Please Me” “Loving You” “Seasons” “Thriller” “Black Ice” “18 Hits” “Man To Man” “Two's Company” “Coda” )

PurchaseDate=( “11/12/2002” “9/23/1988” “1/1/2000” “6/15/1993” “12/19/1990” “3/30/1987” “5/20/2004” “2/19/1995” “5/8/2005” “7/31/2007” )

Cost=( “19.87” “20.00” “21.35” “18.21” “25.99” “30.00” “12.85” “18.00” “25.61” “10.21” )

jschiwal · 02-20-2009, 03:29 PM

If that is the actual form of the file you saved, the lines are also legal bash statements, and you can simply source it.

You are using a strange double quote. If you convert them to simple double quotes `"', then simply run:
. yourfile

After that, you can access the arrays normally.
. tempfile.sh
jschiwal@hpmedia:~> echo ${CDName[0]}
Please Please Me
jschiwal@hpmedia:~> echo ${CDName[1]}
Loving You

Here is an example where I used sed to use the NAME=VALUES results from ogginfo. I eval the results to set variables for a ogg2mp3 script.

Code:

cat bin/get_tags
get_tags()
{
    # clear out old tags
    ALBUM='';
    ARTIST='';
    DATE='';
    GENRE='';
    TITLE='';
    # the tags returned by ogginfo are of the form NAME=VALUE.
    # put single quotes around the values to encapsulate white space.
    # eval will set the tag variables ALBUM, ARTIST, DATE, GENRE, TITLE
    eval $(ogginfo ${1} | sed '/[A-Z][A-Z]*=/!d;s/=\(.*\)$/='"'"'\1'"'"'/;s/^\t//')
}

PatrickNew · 02-20-2009, 03:43 PM

Quote:

Originally Posted by jschiwal

If that is the actual form of the file you saved, the lines are also legal bash statements, and you can simply source it.

You are using a strange double quote. If you convert them to simple double quotes `"', then simply run:
. yourfile

After that, you can access the arrays normally.
. tempfile.sh

That is really cool. I'm adding that to the toolbox.

nobody123 · 02-20-2009, 09:04 PM

Quote:

Originally Posted by jschiwal

If that is the actual form of the file you saved, the lines are also legal bash statements, and you can simply source it.

You are using a strange double quote. If you convert them to simple double quotes `"', then simply run:
. yourfile

After that, you can access the arrays normally.
. tempfile.sh
jschiwal@hpmedia:~> echo ${CDName[0]}
Please Please Me
jschiwal@hpmedia:~> echo ${CDName[1]}
Loving You

Here is an example where I used sed to use the NAME=VALUES results from ogginfo. I eval the results to set variables for a ogg2mp3 script.

Code:

cat bin/get_tags
get_tags()
{
    # clear out old tags
    ALBUM='';
    ARTIST='';
    DATE='';
    GENRE='';
    TITLE='';
    # the tags returned by ogginfo are of the form NAME=VALUE.
    # put single quotes around the values to encapsulate white space.
    # eval will set the tag variables ALBUM, ARTIST, DATE, GENRE, TITLE
    eval $(ogginfo ${1} | sed '/[A-Z][A-Z]*=/!d;s/=\(.*\)$/='"'"'\1'"'"'/;s/^\t//')
}

Thank you jschiwal for your lovely piece of code. The reasons why I had those strange double quotes is because I thought of simulating strings. Then I realized that it is already in a string so there is actually no need

. Anyways, I'll work with your code and get back here when I finally get the script to work the way I want it to. Thank you again!

nobody123 · 03-21-2009, 02:45 PM

I just ended up creating a text file instead of using arrays. Makes it a whole lot easier to get values using grep. Srry for wasting everyone's time.