I want a bash script to add a header line (with generic column names) to a CSV file.
My CSV file content:
a,b,c,d,e,f,g,h,i,j
a,b,c,d,e,f,g,h,i,j
Desired CSV file content:
1,2,3,4,5,6,7,8,9,10
a,b,c,d,e,f,g,h,i,j
a,b,c,d,e,f,g,h,i,j
I have been trying to convert between CSV and ARFF file formats, however the CSV2Arff.java code example from Weka requires the input CSV file to have a header, but my CSV file has none.
Usage:
./add_header.sh "input.csv"
The bash script (i.e. add_header.sh) takes the csv file name as its 1 argument.
timestamp=$(date +"%Y-%m-%d_%H-%M")
input_csv_file=$1
output_csv_file="header_"$timestamp"_"$input_csv_file
o=""
# Find the number of columns (commas) in the first row
n=$(($(head -n1 $input_csv_file | sed 's/[^,]//g' | wc -c)))
for i in $(seq 1 $n); # Get a list of numbers equal to column qty
do
o=$o""$i",";
done
#Write the numbers with commas to first line of new file.
echo $o > $output_csv_file
#Append whole of other file to new file.
cat $input_csv_file >> $output_csv_file
Output: is a new file containing the header (with comma-separated numbered columns) followed by the original CSV file content. e.g.
1,2,3,4,5,6,7,8,9,10,
a,b,c,d,e,f,g,h,i,j
a,b,c,d,e,f,g,h,i,j
this can be done in one line in the shell (bash). For example if using an example file called "dat.csv"
$ cat dat.csv
a,b,c,d,e,f,g,h,i,j
a,b,c,d,e,f,g,h,i,j
then
$ cat <(seq -s, 1 $(( `head -n 1 dat.csv | tr -dc "," | wc -c` + 1 ))) dat.csv
1,2,3,4,5,6,7,8,9,10
a,b,c,d,e,f,g,h,i,j
a,b,c,d,e,f,g,h,i,j
you can put the result in a new file like this:
$ cat <(seq -s, 1 $(( `head -n 1 dat.csv | tr -dc "," | wc -c` + 1 ))) dat.csv > newfile.csv
