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Full Discussion: [stdin / stdout] Strategies for redirecting outputs
Top Forums Shell Programming and Scripting [stdin / stdout] Strategies for redirecting outputs Post 302995684 by bakunin on Monday 10th of April 2017 03:21:39 PM
Old 04-10-2017
My take on this is to first lay down some rules:

1) I do not want to interfere with normal redirection, i.e. if i enter the command:

Code:
# myscript.sh > /some/log

I expect the script not to "overrule" this and put the output to stdout somewhere else than /some/log. It might write it somewhere else too, but finally whatever the output is should go to the file i specified. Analogous for stderr

2) I would like to encapsulate this whole functionality as much as possible. It would be OK to call some_function instead of, say echo, but i would try the utmost to avoid to "decorate" every single output-statement like this:

Code:
if [ $VERBOSE -eq 0 ] ; then
    if [ $LOG -eq 0 ] ; then
       .....
    else
       .....
    fi
else
     if [ $LOG -eq 0 ] ; then
       .....
    else
       .....
    fi
fi

3) If i already go through the trouble of writing a wrapper function for my output i could as well automatically add more than the "naked" output i send as an argument: a timestamp, maybe the process number, name of the calling function or similar information might come in handy when trying to figure out why a script has failed and what exactly has and has not done. If i write in a script:

Code:
....
if do_something ; then
     out_function "successfully executed the something step"
else
     out_function "executing the something step FAILED"
fi

I would like to see exactly this at the screen output (or the file i redirected it at) but maybe something like:

Code:
1.1.2017 00:10 (123456) ERROR: executing the something step FAILED

where (123456) is the process number of the script this was part of.

Having said all this i don't want to spoil your fun of writing such a function, so i will stop here. Post your production once you have it and i will be glad to discuss it with you. In fact i have written (and used) exactly such a function(-set) in my scripts for years, so kudos for your insight to feel the necessity for such a thing.

I hope this helps.

bakunin
 

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LEARN ABOUT SUSE

bf_tar

BF_TAR(1)																 BF_TAR(1)

NAME

       bf_tar - shell script to write a tar file of a bogofilter directory to stdout

SYNOPSIS

       bf_tar [-r] [-R] bogofilter_directory

DESCRIPTION

       bf_tar bundles a bogofilter working directory in tar format and copies it to standard output (your console, or where you redirect it, see
       EXAMPLES below).

OPTIONS

       The -r option causes bf_tar to remove inactive log files after the archive has been written successfully. The default is to leave log
       files.

       The -R option causes bf_tar to remove inactive log files before the archive is written. This may reduce chances that the resulting archive
       is recoverable should it become damaged. The archive may be smaller though. The default is to leave log files.

EXIT STATUS

       The script exits with status code 0 if everything went well, and nonzero if it encountered trouble.

EXAMPLES

       o  bf_tar ~/.bogofilter > outfile.tar

	  Writes a standard .tar file containing the essential files from ~/.bogofilter to outfile.tar.

       o  bf_tar ~/.bogofilter | gzip -9 -c > outfile.tar.gz

	  Writes a gzipped .tar.gz file containing the essential files from ~/.bogofilter to outfile.tar.gz.

       o  bf_tar `pwd`/mydirectory > outfile.tar

	  Prepend $(pwd)/ or `pwd`/ if you want to specify an absolute path instead of a relative path.

NOTES

       This script is meant for use with Berkeley DB based bogofilter versions.

       This script requires a SUSv2 compliant pax utility.

       This script expects a SUSv2 compliant shell. Solaris systems should have the SUNWxcu4 package installed (when bogofilter is configured) so
       that /usr/xpg4/bin/sh can be used.

								    07/23/2007								 BF_TAR(1)
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