I'm having following data in file
Line 1
Now I have to add the three new lines at
line number 3,5,6
but when I use
sed -i '3i string1' file
sed -i '4i string2' file
sed -i '6i string3' file
it is not appending the data unless it having some lines in it.
but when that file is empty then it is not add the data as there is no line number which sed can find.
So how I can able to add this line in file.
You can do:
# insert 5 blank lines into the file
printf "\n%.0s" {1..5} >> file
# now use sed to replace desired line numbers
sed -i '3s/^/string1/; 4s/^/string2/; 6s/^/string3/' file
To take any File and, if needed, add new lines to it as needed to make it at least n lines long:
awk -i inplace -v n=6 'END{for (i=NR;i<=n;i++) print""} 1' File # GNU awk
Or,
awk -v n=6 'END{for (i=NR;i<=n;i++) print""} 1' File >tmp && mv tmp File # BSD/OSX awk
If the file is already n lines long, this does nothing to the file.
After you have done this, your sed commands should work.
