Making a new file using another as template in BASH

Question

I have two files such as:

File_1

c1,c2,c3,c4

File_2

c1,c3,c2,c4

DA,CA,DD,CD

Thus, I want to make a File 3 using the File 1 as model using BASH:

File_3

c1,c2,c3,c4

DA,DD,CA,CD

In this example, the File_1 is a model of the correct disposition of the columns and the File_2 has the columns and their respective informations but in a wrong disposition. Thus, the File_3 used the file_1 as a template and ordered the information in the file_2 in a correct disposition.

In the example I just gave 4 columns, but my real file has 402 columns. So, to do an

awk -F"," '{print $1","$3","$2","$4}' File_2

or something like this, will not work because I dont know the position of the itens of the File_1 in the File_2 (for example the c1 column in the File_2 could be in the sixth, the second, or the last columns positions).

I hope that you can help me using BASH (if possible) and I would like an small explanation of the script, because I'm newbie and I don't know a lot the commands.

Thanks in advance.

kev · Accepted Answer · 2012-03-11 00:54:17Z

1

You can make a header index mapping like this:

File_2  =>  File_1
------      ------
1       =>  1
2       =>  3
3       =>  2
4       =>  4

awk -F, '
    FNR==NR{
        for(i=1;i<=NF;i++)
            a[$i]=i
        print
        nextfile
    }
    FNR==1{
        for(j=1;j<=NF;j++)
            b[j]=a[$j]
        next
    }
    {
        for(k=1;k<=NF;k++)
            printf( "%s%s",$b[k], k==NF?"\n":",")
    }
' File_{1,2}

Note: This command works if File_{1,2} contain no empty lines!

edited Mar 11, 2012 at 0:54

answered Mar 11, 2012 at 0:38

kev

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2 Comments

valentegt Over a year ago

Thanks Kev. It worked perfectly. I had more than 100,000 lines and worked as I wanted and quickly. What site do you encorajous me to read to understand the script?

kev Over a year ago

Just basic awk stuff: for...loop, printf, next/nextfile, NR/FNR. I think you can understand them in several mins.

user unknown · Accepted Answer · 2012-03-11 00:47:51Z

0

If you are free to change the format of file 2 from:

File_2
c1,c3,c2,c4    
DA,CA,DD,CD

to:

s/c1/DA/g
s/c3/CA/g
s/c2/DD/g
s/c4/CD/g

you can use sed:

sed -f File_2 File_1 > File_3

Else you may work with arrays:

key=($(head -n1 File_2 | tr "," " "))
val=($(tail -n1 File_2 | tr "," " "))
len=${#key[*]}
for i in $(seq 0 $((len-1))); do echo s/${key[$i]}/${val[$i]}/g; done > subst.sed 
sed -f subst.sed File_1 > File_3

The generated sed-Program is the one as above. If a substitution matches the key of a following command, you might get unexpected results. If you only like to match whole words, you have to change the sed command a bit.

edited Mar 11, 2012 at 0:47

answered Mar 11, 2012 at 0:32

user unknown

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