Explode to Array

Question

I put together this shell script to do two things:

Change the delimiters in a data file ('::' to ',' in this case)
Select the columns and I want and append them to a new file

It works but I want a better way to do this. I specifically want to find an alternative method for exploding each line into an array. Using command line arguments doesn't seem like the way to go. ANY COMMENTS ARE WELCOME.

    # Takes :: separated file as 1st parameters
    SOURCE=$1

    # create csv target file
    TARGET=${SOURCE/dat/csv}
    touch $TARGET

    echo #userId,itemId > $TARGET

    IFS=","
    while read LINE
    do
        # Replaces all matches of :: with a ,
        CSV_LINE=${LINE//::/,}
        set -- $CSV_LINE
        echo "$1,$2" >> $TARGET
    done < $SOURCE

There has got to be a better title -- please update your title so it is relevant. (-1 for now, for afore mentioned reason, but that can easily be amended later.) — user166390
– user166390, Commented Jun 15, 2012 at 3:35
Place the redirection to $TARGET outside the loop, probably as > $TARGET. You can then lose the touch before the loop. Your title line needs to include quotes (echo "#userID,itemId") too. — Jonathan Leffler
– Jonathan Leffler, Commented Jun 15, 2012 at 3:42

Dennis Williamson · Accepted Answer · 2012-06-15 11:26:32Z

2

Instead of set, you can use an array:

arr=($CSV_LINE)
echo "${arr[0]},${arr[1]}"

answered Jun 15, 2012 at 11:26

Dennis Williamson

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chepner · Accepted Answer · 2012-06-15 13:57:55Z

2

The following would print columns 1 and 2 from infile.dat. Replace with a comma-separated list of the numbered columns you do want.

awk 'BEGIN { IFS='::'; OFS=","; } { print $1, $2 }' infile.dat > infile.csv

answered Jun 15, 2012 at 13:57

chepner

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John3136 · Accepted Answer · 2012-06-15 03:44:41Z

1

Perl probably has a 1 liner to do it.

Awk can probably do it easily too.

My first reaction is a combination of awk and sed:

Sed to convert the delimiters
Awk to process specific columns

cat inputfile | sed -e 's/::/,/g' | awk -F, '{print $1, $2}'
# Or to avoid a UUOC award (and prolong the life of your keyboard by 3 characters
sed -e 's/::/,/g' inputfile | awk -F, '{print $1, $2}'

edited Jun 15, 2012 at 3:44

answered Jun 15, 2012 at 3:30

John3136

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3 Comments

John3136 Over a year ago

Fair comment - never knew I could get an award for it though ;-)

contrapositive Over a year ago

I'll have to find tutorials on sed and awk. Thanks for the example.

Dennis Williamson Over a year ago

That removes the comma. Set OFS = FS in a BEGIN block.

Kevin · Accepted Answer · 2012-06-15 12:22:34Z

1

awk is indeed the right tool for the job here, it's a simple one-liner.

$ cat test.in
a::b::c
d::e::f
g::h::i
$ awk -F:: -v OFS=, '{$1=$1;print;print $2,$3 >> "altfile"}' test.in
a,b,c
d,e,f
g,h,i
$ cat altfile
b,c
e,f
h,i
$

answered Jun 15, 2012 at 12:22

Kevin

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