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Top Forums UNIX for Beginners Questions & Answers Non-interactive & non-login shell environment? Post 303007555 by Corona688 on Friday 17th of November 2017 05:54:26 PM
Old 11-17-2017
Quote:
Originally Posted by bodisha
Thanks for the reply again... You sort of touched on the part of where I'm getting confused at. My understanding of a background process like a user ID for an Oracle database is it would be a non-interactive and non-login shell...
The shell is not actually in charge, it just helps arrange things. The shell isn't necessarily involved at all in creating the Oracle process, or creating any other process for that matter.

The one and only difference between "interactive" and "noninteractive" processes, as far as the kernel is concerned, is whether your process has a controlling terminal. The kernel knows what your terminal is even if your process doesn't - you can open it via /dev/tty. The kernel doesn't really care whether you have a terminal.

In the old days terminals were really terminals - physical devices attached to serial ports. /bin/login did the job of holding those ports open and reading username/passwords from them. Each port would have one /bin/login process running for it. These days, things like ssh have mostly taken over the job of sitting around and waiting for user input, terminals have become imaginary devices which get created and destroyed at need.

The login program creates your shell. It owns the terminal, and opens it, duplicating it onto file descriptors 0, 1, and 2 for you - standard input, standard output, and standard error. Then login runs your shell and lets it take over from there.

Quote:
It specifies a script and not a process... Which makes me wonder how does a background process owned get the environment.
When a process is created, it receives a copy of the environment of its parent. So it comes down to where the parent got its environment.

Last edited by Corona688; 11-17-2017 at 07:00 PM..
 

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SHELL-QUOTE(1p) 					User Contributed Perl Documentation					   SHELL-QUOTE(1p)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.8.4 2005-05-03 SHELL-QUOTE(1p)
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