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Full Discussion: Non-interactive & non-login shell environment?
Top Forums UNIX for Beginners Questions & Answers Non-interactive & non-login shell environment? Post 303007425 by bodisha on Thursday 16th of November 2017 11:13:43 AM
Old 11-16-2017
Non-interactive & non-login shell environment?
Hello and thanks in advance for any help anyone can offer to straighten me out on this subject

I'm trying to understand non-interactive & non-login shells and having a hard time conceptualize the process a non-interactive & non-login shell goes through to start up. Particularly for background processes.

The way I understand things is when a process is started.... a region of memory is created and the child process replicates a duplicate environment of the parent by being forked. What's confusing me is when is the shell environment defined for a background process? When I think about how an interactive shell is started I get a little lost.

The way I understand an interactive shell is:
  1. User passes login ID to Linux kernel
  2. Linux kernel looks the user up in the /etc/password file and identifies the assigned shell
  3. the shell is started
  4. the shell reads the login scripts to define the shell environment for the user
  5. Linux produces a command prompt to indicate the shell is ready to accept commands


Do processes that start in the background have a similar process it steps through? This is how I envision it working:
  1. The process is forked by the parent process
  2. Linux identifies the user ID the process will runs as
  3. Linux looks the user id up in the /etc/passwd file
  4. the shell is started
  5. the BASH_ENV is read (If it was defined)
  6. the process interacts with the shell to pass commands to the API

For example... An Oracle database would have the user ID of oracle and be assigned the /bin/bash shell... Would this process accurately describe what it goes through when it starts?

For some reason this seems clunky and like I'm missing something... Could someone let me know if I'm on the right path please?

Thank you very much!
Last edited by rbatte1; 11-17-2017 at 07:57 AM.. Reason: Formatted numbered lists with LIST=1 tags
 

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LEARN ABOUT HPUX

wait

wait(1) 						      General Commands Manual							   wait(1)

NAME

       wait - await process completion

SYNOPSIS

       [pid]

DESCRIPTION

       If  no argument is specified, waits until all processes (started with of the current shell have completed, and reports on abnormal termina-
       tions.  If a numeric argument pid is given and is the process ID of a background process, waits until that process has  completed.   Other-
       wise, if pid is not a background process, exits without waiting for any processes to complete.

       Because the system call must be executed in the parent process, the shell itself executes without creating a new process (see wait(2)).

   Command-Line Arguments
       supports the following command line arguments:

	      The unsigned decimal integer process
			  ID of a command, whose termination is to wait for.

WARNINGS

       Some processes in a 2-or-more-stage pipeline may not be children of the shell, and thus cannot be waited for.

SEE ALSO

       csh(1), ksh(1), sh-posix(1), sh(1), wait(2).

STANDARDS CONFORMANCE

																	   wait(1)
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