On 25Oct2017 14:24, GianPiero Puccioni <gianpiero.puccioni@xxxxxxxxxx> wrote:
I have a question about the system startup files for bash.
The problem I had was that I set up an alias in ~/.bashrc, let's say
alias ls="ls -lh"
but it didn't work as "alias ls" reported
alias ls='ls --color=auto'
What happens is that at the end ~/.bashrc sources /etc/bashrc which sources
/etc/profile.d/*.sh that redefine "ll".
This happens on F24, F25, F26 and CentOS....
Easy to correct, but the question is: is that right? None of the
examples I found on line does that and /etc/profile.d/*.sh are already
sourced by /etc/profile (which is the first startup file read on
login). Is this a quirk of RedHat or an error that still remains in the files
or what?
There are at least 2 things wrong.
First, the .bashrc (which one presumes first came from the template in
/etc/skel) should source /etc/bashrc _first_, not last.
Second, /etc/bashrc should _not_ be sourcing anything in /etc/profile.d. That
is for _login_ shells.
Have a look at the "INVOCATION" section of "man bash".
Bash has roughly 3 modes: batch mode, interactive mode and login mode.
Batch mode is used to run scripts. It should basicly source nothing new.
An interactive shell should source your .bashrc, to get settings useful for
interactive use (convenience aliases like your "ls", prompt settings, etc).
A login shell should source /etc/profile, to get per login fuller settings (set
up your $PATH, and so forth, often more expensive than plain "interactive"
shells). It is very common for this in turn to source your .bashrc as a final
act if the shell is also interactive.
So the bashrc has _no_ business sourcing /etc/profile or /etc/profile.d.
In the modern world (GUI desktop) the picture is complicated and what you're
observing is probably a consequence of bad decisions to address that
complication.
In ancient times, one logged in on a serial terminal, or less anciently, on a
text mode PC console. You started a single login shell, which ran /etc/profile
once, setting up your environment. All subshells would be interactive, sourcing
the .bashrc (or equivalent) for interactive settings like convenience aliases.
You might then start X11 to get a GUI desktop, and reasonably all the terminal
emulators you then run would just run plain interactive shells, since your
/etc/profile had already happened.
With a GUI login, the desktop starts up and the terminals you might invoke
don't have the benefit of an original sourcing of /etc/profile (unless you've
made personal efforts to that end, as I do).
As a consequence, GUI desktop often start terminals with shells in "login" mode
inside them, expressly to ensure that you get your /etc/profile and .profile
sourced. Slower but gets it done. On a modern machine the performance issue is
usually minor.
However, terminal emulators might not do that. So someone in bash install setup
land for the various distros has taken it upon themselves to make ordinary
interactive shells act like login shells. Gah! Overkill.
However, that is the kind of decision that leads to the bashrc sourcing
/etc/profile stuff.
Hoping this explains the situation somewhat.
Cheers,
Cameron Simpson <cs@xxxxxxxxxx> (formerly cs@xxxxxxxxxx)
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