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Top Forums Shell Programming and Scripting [stdin / stdout] Strategies for redirecting outputs Post 302995680 by MadeInGermany on Monday 10th of April 2017 02:48:58 PM
Old 04-10-2017
Quote:
Originally Posted by Marmz
Well.. let's say i need to write a pretty simple script.

In my script i have 2 variables which can have value of 0 or 1.
  • $VERBOSE
  • $LOG

I need to implement these cases:
  1. ($VERBOSE = 0 && $LOG = 0) => ONLY ERROR output (STDERR to console && STDOUT to /dev/null)
  2. ($VERBOSE = 1 && $LOG = 0) => VERBOSE output (ALL to console)
  3. ($VERBOSE = 0 && $LOG = 1) => LOG output (ALL to file.log)
  4. ($VERBOSE = 1 && $LOG = 1) => BOTH output (ALL to console && ALL to file.log)


For now i got to understand i can do the following to put EVERYTHING to a file
Code:
exec > file.log                                                                    
exec 2>&1

Sure it is a very known argument.. but i'd like to hear some opinion Smilie
Code:
logfile=file.log
if [ $VERBOSE = 0 -a $LOG = 0 ] ; then
  exec 2>> /dev/null
elif [ $VERBOSE = 1 -a $LOG = 0 ] ; then
  :
elif [ $VERBOSE = 0 -a $LOG = 1 ] ; then
  >> $logfile 2>&1
else
  echo "output goes to $logfile"
  >> $logfile
fi

For the latter case to go to *both* file and console, you would need a pipe to tee for the following code, e.g. by means of enclosing the code with { }:
Code:
{
# block starts, see redirection at the end
: code
# redirect this block to
} 2>&1 | tee -a $logfile

 

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service(8)						      System Manager's Manual							service(8)

NAME
service - run a System V init script SYNOPSIS
service SCRIPT COMMAND [OPTIONS] service --status-all service --help | -h | --version DESCRIPTION
service runs a System V init script in as predictable environment as possible, removing most environment variables and with current working directory set to /. The SCRIPT parameter specifies a System V init script, located in /etc/init.d/SCRIPT. The supported values of COMMAND depend on the invoked script, service passes COMMAND and OPTIONS it to the init script unmodified. All scripts should support at least the start and stop commands. As a special case, if COMMAND is --full-restart, the script is run twice, first with the stop command, then with the start command. service --status-all runs all init scripts, in alphabetical order, with the status command. EXIT CODES
service calls the init script and returns the status returned by it. FILES
/etc/init.d The directory containing System V init scripts. ENVIRONMENT
LANG, TERM The only environment variables passed to the init scripts. SEE ALSO
/etc/init.d/skeleton, update-rc.d(8), init(8), invoke-rc.d(8). Jan 2006 service(8)
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