Running Shell Script And Redirect To Log File?

jedipi

May 19 2005, 11:33 AM

I have a shell script like this:

while true
do
sh a.sh
sh b.sh
done

now I want the script not just call and run a.sh and b.sh, but also output some log files.
here is what I did:

while true
do
sh a.sh
sh a.sh >>log
sh b.sh
sh b.sh >>log
done

I know this is not a good way....
is there any better way to do it??
Thank you

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qwijibow

May 19 2005, 12:26 PM

that IS a good way, thats te way you are meant to do it

you may want to tweak what shell output can, and cannot be logged.

CODE

sh a.sh | grep LOG >> log

this will only log lines with the word "LOG" in them.. for example
"LOG: 1:00pm, and all is well."

EDIT:
just noticed

QUOTE

while true
do
sh a.sh
sh a.sh >>log
sh b.sh
sh b.sh >>log
done

So, you want the script to print to the console, AND write to the log..
yes, there is a much better way, you dont need to run the script twice.

use a variable to store the output..

this code example run the porgram "uptime" and outputs its result to the scree, and a logfile.
the variable name is called CURRENT_UPTIME

CODE

#!/bin/bash

CURRENT_UPTIME=`uptime`

# print to screen.
echo $CURRENT_UPTIME

#print to log
echo $CURRENT_UPTIME >> log

EDIT2:
it not clear on this forum, but those ` marks are the single back tilted quotes... using the normal ' will not work.

on my keyboard, the ` (correct mark) is the one below the ESC key.

in BASH shell programming, all 3 different quote marks have different meanings.

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signatureimage

May 19 2005, 12:41 PM

Dear jedipi,

I coudn't help but notice in your example that you executed the shell commands two times:

CODE

sh a.sh
sh a.sh >>log

I suppose that the first execution was done to obtain the output on the console screen, and the second execution was done to obtain the output inside a file - what you call a log-file.

The danger here is that in some cases, it could be possible that the result would not be exactly the same - for instance when a time-dependent value was produced by the shell command.

There exists a shortcut to obtain the desired result by executing the bash script just once.

CODE

sh a.sh | tee log

The tee command is one of those odd little specialized Unix commands that come in handy at the strangest times. It both displays the command output on the screen, and stores it in a file. Use tee -a to append, instead of overwrite.

So, for the second bash script, we will use:

CODE

sh b.sh | tee -a log

I hope that I have interpreted your question correctly, and that my proposal will help you.

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qwijibow

May 19 2005, 12:46 PM

lol, looks like we both posted at the same time, with different solutions.

you should probably use signatureimage's solution, same results, minus the need for variables.

been using bash for years, and thats the first time ive heard of that command (and yep, its installed on my system)

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jedipi

May 20 2005, 05:40 AM

QUOTE (qwijibow @ May 19 2005, 11:46 PM)

thanks for you guys solutions.

With this tee command, I can split the output stream.
so that it is both displayed on screen and also re-direct it to a file.

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