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Full Discussion: Understanding the difference between individual BASH login scripts
Top Forums UNIX for Beginners Questions & Answers Understanding the difference between individual BASH login scripts Post 303006891 by Corona688 on Wednesday 8th of November 2017 05:35:36 PM
Old 11-08-2017
First off, these files are shell scripts, so they do whatever their author wanted. This is responsible for a lot of the confusion - /etc/bashrc is not a file bash will load unless something else tells it to, but someone could easily have put . /etc/bashrc into /etc/profile for the same effect. You have to read these profile scripts to see what they do, no other way to know.

Code:
man bash

...

FILES
...
       /etc/profile
              The systemwide initialization file, executed for login shells
       ~/.bash_profile
              The personal initialization file, executed for login shells
       ~/.bashrc
              The individual per-interactive-shell startup file
       ~/.bash_logout
              The individual login shell cleanup file, executed when  a  login
              shell exits
...

These are the files bash loads and when it loads them. Anything else is a command someone dropped into one of those files.

Quote:
I've seen people posting about how one command (like umask) would work in one script but not another and I haven't seen a clear cut definition of which scripts should contain what
Imagine this script:

Code:
#!/bin/bash

cd /etc

Set the file executable and run it with ./changedir.sh and it will create a new shell, change directory to /etc/ in that new shell, and die, leaving you in your original shell which is still wherever you left it.

If you run that script with . changedir.sh on the other hand - note the space - that instructs your own shell to load and run that code, and it will actually move your current shell.

And if you run cd /etc/ first, then run that script, the new shell will already have /etc/ as its current directory, copying it from yours.

cd, umask, and variables in general are like that. If you run it in your shell, new shells created afterewards get copies of those settings, otherwise, each process is independent.

Init scripts like /etc/profile, et cetera, all run inside your current shell anyway.
 

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LEARN ABOUT XFREE86

chsh

CHSH(1)                                                            User Commands                                                           CHSH(1)

NAME

       chsh - change login shell

SYNOPSIS

       chsh [options] [LOGIN]

DESCRIPTION

       The chsh command changes the user login shell. This determines the name of the user's initial login command. A normal user may only change
       the login shell for her own account; the superuser may change the login shell for any account.

OPTIONS

       The options which apply to the chsh command are:

       -h, --help
           Display help message and exit.

       -R, --root CHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.

       -s, --shell SHELL
           The name of the user's new login shell. Setting this field to blank causes the system to select the default login shell.

       If the -s option is not selected, chsh operates in an interactive fashion, prompting the user with the current login shell. Enter the new
       value to change the shell, or leave the line blank to use the current one. The current shell is displayed between a pair of [ ] marks.

NOTE

       The only restriction placed on the login shell is that the command name must be listed in /etc/shells, unless the invoker is the superuser,
       and then any value may be added. An account with a restricted login shell may not change her login shell. For this reason, placing /bin/rsh
       in /etc/shells is discouraged since accidentally changing to a restricted shell would prevent the user from ever changing her login shell
       back to its original value.

FILES

       /etc/passwd
           User account information.

       /etc/shells
           List of valid login shells.

       /etc/login.defs
           Shadow password suite configuration.

SEE ALSO

       chfn(1), login.defs(5), passwd(5).

shadow-utils 4.5                                                    01/25/2018                                                             CHSH(1)
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