I want to add a row of headers to an existing CSV file, editing in place. How can I do this?
echo 'one, two, three' > testfile.csv
and I want to end up with
column1, column2, column3
one, two, three
Changing the initial CSV output is out of my hands.
Any standard command will do. The important thing is the file is edited in place, and the line is inserted at the beginning of the file.
To answer your original question, here's how with sed:
sed -i '1icolumn1, column2, column3' testfile.csv
The 1i command tells sed to go to line 1 and insert the text there.
The -i option causes the file to be edited "in place" and can also take an optional argument, ~, to create a backup file. For example:
sed -i~ '1icolumn1, column2, column3' testfile.csv
would keep the original file in "testfile.csv~".
This adds custom text at the beginning of your file:
echo 'your_custom_escaped_content' > temp_file.csv
cat testfile.csv >> temp_file.csv
mv temp_file.csv testfile.csv
Without sed, you can use >> to append to a file. For example:
echo 'one, two, three' >> testfile.csv
To prepend to a file, try something like:
echo "text"|cat - yourfile > /tmp/out && mv /tmp/out yourfile
echo "text"|cat - sourcefile | gzip >tmpfile.gz; rm -f sourcefile; ungzip tmpfile.gzAs far as I understand, you want to prepend column1, column2, column3 to your existing one, two, three.
I would use ed in place of sed, since sed writes to stdout instead of the file:
printf '0a\ncolumn1, column2, column3\n.\nw\n' | ed testfile.csv
perl -i is worth taking a look at as well.
printf 'hello world' >> testfile.txt
printf '%s\n' 0a "column1, column2, column3" . w as possibly clearer than lots of embedded \n.sed is line based, so I'm not sure why you want to do this with sed. The paradigm is more processing one line at a time( you could also programatically find the # of fields in the CSV and generate your header line with awk) Why not just
echo "c1, c2, ... " >> file
cat testfile.csv >> file
?
Add a given line at the beginning of a file in two commands:
cat <(echo "blablabla") input_file.txt > tmp_file.txt
mv tmp_file.txt input_file.txt
To make an in-place change, the correct tool is ed:
ed testfile.csv <<END
0i
column1, column2, column3
.
wq
END
Unlike sed -i or any shell function using mv, this overwrites the file with the new contents, rather than replacing with a new file.
how to add line inside a file
sed -i -e "48r../../../../folder1/lines_to_add.txt" a.txt
a.txt - the file you want to change 48r is line number of a.txt some lines are inside lines_to_add.txt file
../../../../scripts3_2d/lines_to_add.txt
-i update a.txt, try without -i before run the code, be careful with new lines,
"keep a newline at the end of lines_to_add.txt"
