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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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AC(8)							    BSD System Manager's Manual 						     AC(8)

NAME
ac -- connect time accounting SYNOPSIS
ac [-dp] [-t tty] [-w wtmp] [users ...] DESCRIPTION
If the file /var/log/utx.log exists, a record of individual login and logout times are written to it by login(1) and init(8), respectively. The ac utility examines these records and writes the accumulated connect time (in hours) for all logins to the standard output. The options are as follows: -d Display the connect times in 24 hour chunks. -p Print individual users' totals. -t tty Only do accounting logins on certain ttys. The tty specification can start with '!' to indicate not this tty and end with '*' to indicate all similarly named ttys. Multiple -t flags may be specified. -w wtmp Read connect time data from wtmp instead of the default file, /var/log/utx.log. users ... Display totals for the given individuals only. If no arguments are given, ac displays the total connect time for all accounts with login sessions recorded in utx.log. The default utx.log file will increase without bound unless it is truncated. It is normally truncated by the daily scripts run by cron(8), which rename and rotate the utx.log files, keeping a week's worth of data on hand. No login or connect time accounting is performed if /var/log/utx.log does not exist. FILES
/var/log/utx.log connect time accounting file EXIT STATUS
The ac utility exits 0 on success, and >0 if an error occurs. EXAMPLES
Allow times recorded in modems to be charged out at a different rate than other: ac -p -t "ttyd*" > modems ac -p -t "!ttyd*" > other SEE ALSO
login(1), getutxent(3), init(8), sa(8) BSD
January 21, 2010 BSD
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