Logging to a file, prepending a timestamp to each line (Debian)

I am trying to log output from some shell scripts of mine to a file, and I want the timestamp prepended to each line. From what I understood, that's what logger(1) is for, but I don't want the output to go to /var/log/messages, and I can't see that this is possible using logger. I'm using Debian by the way.

What is the best way to do this?

—Oliver

logger's function is actually to shunt messages to syslog; default configs will prepend a timestamp and write the logs out to /var/log/messages, but that doesn't mean that logger's purpose is to prepend a timestamp.

One way to handle this would be to modify your syslog configs such that your messages routed via logger go to a special file - use the "-p" flag to logger to stipulate a facility.priority pair (perhaps one of the user[1..7] facilities), and configure your syslogd to log that facility to a special file.

Alternatively, you could whip up a quick shell function to simply prepend the timestamp:

Bodacious:~ james$ timestamp () {
> f=`date`
> echo $f $*
> }
You have new mail in /var/mail/james
Bodacious:~ james$ timestamp a line of logs
Tue 18 Jan 2011 22:40:24 EST a line of logs
Bodacious:~ james$ 

On my system, this is going to result in the shell forking /bin/date once per line of output. This is inefficient, but probably acceptable at small scales.

I needed something like that, and google got me here. Using something like syslog is definitely an overkill for just trying out to time something, and the printout-every-second is too inconvenient.

Here's a one-liner that seems to work fine:

cmd | { while read R; do echo "$(date +%s) $R"; done }

and a variant that prints the time it took to produce each line:

cmd | { T=$(date +%s); while read R; do T2=$(date +%s); echo "$((T2-T)) $R"; T=$T2; done }

(This is using seconds, probably not too hard to throw in %N in there, but at that level a shell solution is probably not the right tool anyway.)