Adding header to all .csv files in folder and include filename - csv

Question

I'm a command line newbie and I'm trying to figure out how I can add a header to multiple .csv files. The new header should have the following: 'TaxID' and 'filename'
I've tried multiple commands like sed, ed, awk, echo but if it worked it only changed the first file it found (I said *.csv in my command) and I can only manage this for TaxID.
Can anyone help me to get the filename into the header as well and do this for all my csv files?
(Note, I'm using a Mac)
Thank you!

Answer 1

Here's one way to do it, there are certainly others:
$ for i in *.csv;do echo $i;cp "$i" "$i.bak" && { echo "TaxID,$i"; cat "$i.bak"; } >"$i";done
Here's a sample run:
$ cat file1.csv
1,2
3,4
$ cat file2.csv
a,b
c,d
$ for i in *.csv;do echo $i;cp "$i" "$i.bak" && { echo "TaxID,$i"; cat "$i.bak"; } >"$i";done
file1.csv
file2.csv
$ cat file1.csv.bak
1,2
3,4
$ cat file1.csv
TaxID,file1.csv
1,2
3,4
$ cat file2.csv.bak
a,b
c,d
$ cat file2.csv
TaxID,file2.csv
a,b
c,d
Breaking it down:
$ for i in *.csv; do
This loops over all the files ending in .csv in the current directory. Each will be put in the shell variable i in turn.
echo $i;
This just echoes the current filename so you can see the progress. This can be safely left out.
cp "$i" "$i.bak"
Copy the current file (whose name is in i) to a backup. This is both to preserve the file if something goes awry, and gives subsequent commands something to copy from.
&&
Only run the subsequent commands if the cp succeeds. If you can't make a backup, don't continue.
{
Start a group command.
echo "TaxID,$i";
Output the desired header.
cat "$i.bak";
Output the original file.
}
End the group command.
>"$i";
Redirect the output of the group command (the new header and the contents of the original file) to the original file. This completes one file.
done
Finish the loop over all the files.
For fun, here are a couple of other ways (one JRD beat me to), including one using ed!
$ for i in *.csv;do echo $i;perl -p -i.bak -e 'print "TaxID,$ARGV\n" if $. == 1' "$i";done
$ for i in *.csv;do echo $i;echo -e "1i\nTaxID,$i\n.\nw\nq\n" | ed "$i";done

Answer 2

Here is on way in perl that modifies the files in place by adding a header of TaxID,{filename}, ignoring adding the header if it thinks it already exists.
ls
a.csv b.csv
cat a.csv
1,a.txt
2,b.txt
cat b.csv
3,c.txt
4,d.txt
ls *.csv | xargs -I{} -n 1 \
perl -p -i -e 'print "TaxID,{}\n" if !m#^TaxID# && !$h; $h = 1;' {}
cat a.csv
TaxID,a.csv
1,a.txt
2,b.txt
cat b.csv
TaxID,b.csv
3,c.txt
4,d.txt
You may want to create some backups of your files, or run on a few sample copies before running in earnest.
Explanatory:
List all files in directory with .csv extenstion
ls *.csv
"Pipe" the output of ls command into xargs so the perl command can run for each file. -I{} allows the filename to be subsequently referenced with {}. -n tells xargs to only pass 1 file at a time to perl.
| xargs -I{} -n 1
-p print each line of the input (file)
-i modifying the file in place
-e execute the following code
perl -p -i -e
Perl will implicitly loop over each line of the file and print it (due to -p). Print the header if we have not printed the header already and the current line doesn't already look like a header.
'print "TaxID,{}\n" if !m#^TaxID# && !$h; $h = 1;'
This is replaced with the filename.
{}
All told, in this example the commands to be run would be:
perl -p -i -e 'print "TaxID,{}\n" if !m#^TaxID# && !$h; $h = 1;' a.csv
perl -p -i -e 'print "TaxID,{}\n" if !m#^TaxID# && !$h; $h = 1;' b.csv
perl -p -i -e 'print "TaxID,{}\n" if !m#^TaxID# && !$h; $h = 1;' c.csv
perl -p -i -e 'print "TaxID,{}\n" if !m#^TaxID# && !$h; $h = 1;' d.csv