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.
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
?
Use perl -i, with a command that replaces the beginning of line 1 with what you want to insert (the .bk will have the effect that your original file is backed up):
perl -i.bk -pe 's/^/column1, column2, column3\n/ if($.==1)' testfile.csv
sed is line based, so I'm not sure why you want to do this with sed. The paradigm is more processing one line at a time( you could also programatically find the # of fields in the CSV and generate your header line with awk) Why not just
echo "c1, c2, ... " >> file
cat testfile.csv >> file
?
To answer your original question, here's how you do it with sed:
sed -i '1icolumn1, column2, column3' testfile.csv
The "1i" command tells sed to go to line 1 and insert the text there.
The -i option causes the file to be edited "in place" and can also take an optional argument to create a backup file, for example
sed -i~ '1icolumn1, column2, column3' testfile.csv
would keep the original file in "testfile.csv~".
Use perl -i, with a command that replaces the beginning of line 1 with what you want to insert (the .bk will have the effect that your original file is backed up):
perl -i.bk -pe 's/^/column1, column2, column3\n/ if($.==1)' testfile.csv
As 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 write on the standard output and not in the file.
The command:
printf '0a\ncolumn1, column2, column3\n.\nw\n' | ed testfile.csv
should do the work.
perl -i is worth taking a look as well.
To answer your original question, here's how you do it 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 doesn't use sed, but using >> will append to a file. For example:
echo 'one, two, three' >> testfile.csv
Edit: To prepend to a file, try something like this:
echo "text"|cat - yourfile > /tmp/out && mv /tmp/out yourfile
I found this through a quick Google search.
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
?
This doesn't use sed, but using >> will append to a file. For example:
echo 'one, two, three' >> testfile.csv
Edit: To prepend to a file, try something like this:
echo "text"|cat - yourfile > /tmp/out && mv /tmp/out yourfile
I found this through a quick Google search.
Use perl -i, with a command that replaces the beginning of line 1 with what you want to insert (the .bk will have the effect that your original file is backed up):
perl -i.bk -pe 's/^/column1, column2, column3\n/ if($.==1)' testfile.csv
This doesn't use sed, but using >> will append to a file. For example:
echo 'one, two, three' >> testfile.csv
Edit: To prepend to a file, try something like this:
echo "text"|cat - yourfile > /tmp/out && mv /tmp/out yourfile
I found this through a quick Google search.
Add a given line at the beginning of a file in two commands:
cat <(echo "blablabla") input_file.txt > tmp_file.txt
mv tmp_file.txt input_file.txt
This doesn't use sed, but using >> will append to a file. For example:
echo 'one, two, three' >> testfile.csv
Edit: To prepend to a file, try something like this:
echo "text"|cat - yourfile > /tmp/out && mv /tmp/out yourfile
I found this through a quick Google search.
Add a given line at the beginning of a file in two commands:
cat <(echo "blablabla") input_file.txt > tmp_file.txt
mv tmp_file.txt input_file.txt
As far as I understand, you want to prepend column1, column2, column3 to your existing one, two, three.
I would use ed in place of sed, since sed write on the standard output and not in the file.
The command:
printf '0a\ncolumn1, column2, column3\n.\nw\n' | ed testfile.csv
should do the work.
perl -i is worth taking a look as well.
Use perl -i, with a command that replaces the beginning of line 1 with what you want to insert (the .bk will have the effect that your original file is backed up):
perl -i.bk -pe 's/^/column1, column2, column3\n/ if($.==1)' testfile.csv
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
?
As 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 write on the standard output and not in the file.
The command:
printf '0a\ncolumn1, column2, column3\n.\nw\n' | ed testfile.csv
should do the work.
perl -i is worth taking a look as well.
To answer your original question, here's how you do it 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~".
Source: Stackoverflow.com