Insert lines on top of a text file

micronemo · 08-08-2012, 02:10 PM

hello, i must insert output of echo "$(date +%Y%m%d%H%M%S) Inizio backup" on top of text file pippo.log . can you help me with awk or sed command. thanks very very much

Tinkster · 08-08-2012, 02:45 PM

Hi, welcome to LQ!

How about something like this?

Code:

(echo Blah && cat backup) > backup.tmp && mv backup.tmp backup

Cheers,
Tink

micronemo · 08-08-2012, 03:23 PM

thanks, but can't create temporary file , i must do it with i single command.
i try with this but i don't know how complete this:
echo "$(date +%Y%m%d%H%M%S) Inizio backup" | sed -e ' ????1i' /root/pippo.log

Tinkster · 08-08-2012, 05:40 PM

Code:

sed -i "1i""$(echo \"$(date +%Y%m%d%H%M%S) Inizio backup\")" /root/pippo.log

micronemo · 08-08-2012, 06:02 PM

thank very very much
work very well

Tinkster · 08-08-2012, 06:09 PM

Welcome ... sorry about the duplicated echo :) .. I'm sure you got
that sorted yourself, though ;)

micronemo · 08-09-2012, 04:25 AM

there is a little problrem if the file "pippo.log" is empty don't add the line in sed command

Tinkster · 08-09-2012, 04:10 PM

Can you please rephrase that? I don't understand what a) the problem and b) the
desired result is ... :)

micronemo · 08-09-2012, 04:22 PM

if pippo.log contains one or more lines your command work very well but if pippo.log is empty your command don't work.
i must have a command that work with empty file and not empty file
thanks

Tinkster · 08-09-2012, 04:39 PM

You won't be able to do this with a sed one-liner I'm afraid, sed operates on lines.
Write a wrapper script.

Code:

if [ `cat /root/pippo.log 2>/dev/null |wc -l` -eq 0 ]; then
  echo "" > /root/pippo.log
fi
sed -i "1i""$(echo \"$(date +%Y%m%d%H%M%S) Inizio backup\")" /root/pippo.log

micronemo · 08-09-2012, 05:14 PM

thanks