BASH: How to print CSV file out with column headers as separate lines

Question

I have a 2-line CSV file. 1 line is the header, one line is the data. This was pulled from an asset database while looking for data for just one asset. However, please note that the CSV file could conceivably contain more than just 2 lines.

I need to take the CSV (example below) and print each header entry on a separate line, with the matching data entry on the same line.

Sample CSV data

head1,head2,head3,head4
data1,data2,data3,data4

Sample output

head1   data1
head2   data2
head3   data3
head4   data4

How can this be done simply?

gile · Accepted Answer · 2016-11-09 08:42:09Z

1

#!/bin/bash

    while { read -r line1; read -r line2; } do
       IFS=', ' read -r -a array1 <<< "$line1"
       IFS=', ' read -r -a array2 <<< "$line2"

       for index in "${!array1[@]}"
       do
           echo "${array1[index]} ${array2[index]}"
       done
    done < $1

Edited my previous answer. By nesting loops it handles more than two lines and multiple columns.

edited Nov 9, 2016 at 8:42

answered Nov 8, 2016 at 1:29

gile

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Comments

Ipor Sircer · Accepted Answer · 2016-11-08 00:49:34Z

0

With pure bash only:

while IFS=", " read a b c d e f g h;do echo -e "$a\t$e\n$b\t$f\n$c\t$g\n$d\t$h";done <<< $(echo $(<data.csv) )

answered Nov 8, 2016 at 0:49

Ipor Sircer

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2 Comments

Speeddymon Over a year ago

That assumes static data size (number of columns, etc). Unfortunately, the number of columns is dynamic which is why I prefer the output like this.

Speeddymon Over a year ago

Additionally, that assumes that we will know the number of columns ahead of time, which we won't. I have updated the original post.

Speeddymon · Accepted Answer · 2016-11-08 00:53:50Z

Given that I wanted to read in from a file, I did not like the idea of output to another file which I would later have to clean up, hence I went with an associative array, which is available in BASH v4 and up only with builtin command declare -A

This will not work in BASH v3 or lower as -A is not a valid flag to the declare builtin.

Since there are known to only be 2 lines in this file, this is a fairly ugly solution that works well. It could be modified to accommodate additional lines, by adding a nested for loop within the final for loop however then you could run into other issues with line width and line wrapping, upon output.

NF=$(awk -F, 'NR==1{print NF}' temp.txt)
declare -A temparray
for ((i=1;i<=$NF;++i))
do
    temparray[0,$i]+="$(awk -v VAR=$i -F, 'NR==1{print $VAR}' temp.txt)"
done
for ((i=1;i<=$NF;++i))
do
    temparray[1,$i]+="$(awk -v VAR=$i -F, 'NR==2{print $VAR}' temp.txt)"
done
for ((i=1;i<=$NF;++i))
do
    printf "%-45s %s\n" "${temparray[0,$i]}" "${temparray[1,$i]}"
done
unset temparray

c4f4t0r · Accepted Answer · 2016-11-08 01:05:26Z

0

Using bash, this works only if you what two lines.

n=0

while read line;do echo ${line//,/\\n} > file$n ; let n++;done < L

paste file0 file1
head1   data1
head2   data2
head3   data3
head4   data4

answered Nov 8, 2016 at 1:05

c4f4t0r

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2 Comments

Speeddymon Over a year ago

This is using 2 different files as input. Not sure where that came from but I'm not splitting out the data into 2 separate files.

c4f4t0r Over a year ago

@Speeddymon I inserted all the data in file named L and after that I splited in twos files and used paste command

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