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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

git-sh-setup

GIT-SH-SETUP(1) 						    Git Manual							   GIT-SH-SETUP(1)

NAME

       git-sh-setup - Common git shell script setup code

SYNOPSIS

       . "$(git --exec-path)/git-sh-setup"

DESCRIPTION

       This is not a command the end user would want to run. Ever. This documentation is meant for people who are studying the Porcelain-ish
       scripts and/or are writing new ones.

       The git sh-setup scriptlet is designed to be sourced (using .) by other shell scripts to set up some variables pointing at the normal git
       directories and a few helper shell functions.

       Before sourcing it, your script should set up a few variables; USAGE (and LONG_USAGE, if any) is used to define message given by usage()
       shell function. SUBDIRECTORY_OK can be set if the script can run from a subdirectory of the working tree (some commands do not).

       The scriptlet sets GIT_DIR and GIT_OBJECT_DIRECTORY shell variables, but does not export them to the environment.

FUNCTIONS

       die
	   exit after emitting the supplied error message to the standard error stream.

       usage
	   die with the usage message.

       set_reflog_action
	   set the message that will be recorded to describe the end-user action in the reflog, when the script updates a ref.

       git_editor
	   runs an editor of user's choice (GIT_EDITOR, core.editor, VISUAL or EDITOR) on a given file, but error out if no editor is specified
	   and the terminal is dumb.

       is_bare_repository
	   outputs true or false to the standard output stream to indicate if the repository is a bare repository (i.e. without an associated
	   working tree).

       cd_to_toplevel
	   runs chdir to the toplevel of the working tree.

       require_work_tree
	   checks if the repository is a bare repository, and dies if so. Used by scripts that require working tree (e.g.  checkout).

       get_author_ident_from_commit
	   outputs code for use with eval to set the GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL and GIT_AUTHOR_DATE variables for a given commit.

AUTHOR

       Written by Linus Torvalds <torvalds@osdl.org[1]>

DOCUMENTATION

       Documentation by Junio C Hamano and the git-list <git@vger.kernel.org[2]>.

GIT

       Part of the git(1) suite

NOTES

	1. torvalds@osdl.org
	   mailto:torvalds@osdl.org

	2. git@vger.kernel.org
	   mailto:git@vger.kernel.org

Git 1.7.1							    07/05/2010							   GIT-SH-SETUP(1)
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