how to change environment variable permanently

[Anil F Duggirala]

hello,
I would like to change the $PATH environment variable permanently, to
be able to execute a program more quickly.
I have tried adding a new line: export PATH=$PATH:/my/path , to my
.bashrc .
When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
my directory has been appended twice.
I don't know exactly what the "export" command actually does, so I am
lost here.
thanks for your help.

[George N. White III]

On Fri, Jun 24, 2022 at 9:09 AM Anil F Duggirala <anilduggirala(a)fastmail.fm&gt;
wrote:

>  hello,
>  I would like to change the $PATH environment variable permanently, to
>  be able to execute a program more quickly.
>  I have tried adding a new line: export PATH=$PATH:/my/path , to my
>  .bashrc .
>  When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
>  my directory has been appended twice.
>  I don't know exactly what the "export" command actually does, so I am
>  lost here.
>  
I expect many other command-line tools are also unknown to you.  Adjusting
the
PATH setting may not be the best solution if you just want to run one
program.
You can add your program to the GUI configuration to start it with an icon,
put a
symbolic link to the program in a directory that is already in the PATH,
such as
$HOME/bin, create a shell script that runs the program with additional
environment
settings, and many more depending on how the program is used.

Once your linux usage moves beyond web browsing it is important to master
some
basic command-line/shell tools.  There are many dangerously misleading
youtube
tutorials (avoid those that claim to be easy or fast!) and a few that are
excellent, but I
suggest starting with LinuxCommand.org as it has been used by many people
for
years.

If the directory you want to add to the PATH contains a single program,
other methods
are probably more appropriate.   The reason the PATH is added twice is that
~/.bashrc
gets run each time bash is invoked.   If you log in on a text console you
normally see one
entry in the PATH.   If you are in a bash terminal session and see 2
entries, starting bash
again will give 3 entries.

On Fedora, /etc/profile defines a shell function called pathmunge that
checks to see if
a directory is already in the PATH before adding it to the PATH.




>  thanks for your help.
>  
-- 
George N. White III

[Anil F Duggirala]

On Fri, 2022-06-24 at 11:49 -0300, George N. White III wrote:
>  
>  You can add your program to the GUI configuration to start it with an
>  icon, put a 
>  symbolic link to the program in a directory that is already in the
>  PATH, such as 
>  $HOME/bin, create a shell script that runs the program with
>  additional environment 
>  settings, and many more depending on how the program is used. 
Thanks George. I know I can create a Gnome launcher to do this, but
thats not really what I wanted. In Gnome, alt-F2 will open a little
window that lets me issue a command line instruction (like executing a
program), I like that, its fast and easy. I like the idea of just
adding a symbolic link to ~/bin, that path is in my $PATH variable but
the folder doesn't exist, yet.

>  Once your linux usage moves beyond web browsing it is important to
>  master some
>  basic command-line/shell tools.   
Ouch, web browsing, that hurt a little.

>  There are many dangerously misleading youtube
>  tutorials (avoid those that claim to be easy or fast!) and a few that
>  are excellent, but I 
>  suggest starting with LinuxCommand.org as it has been used by many
>  people for 
>  years. 
Thanks for this reference, I will look it up. Right now I am reading a
book called, How Linux Works by Brian Ward.

>  If the directory you want to add to the PATH contains a single
>  program, other methods
>  are probably more appropriate.    
Ok, that makes sense.

>  The reason the PATH is added twice is that ~/.bashrc
>  gets run each time bash is invoked.   If you log in on a text console
>  you normally see one
>  entry in the PATH.   If you are in a bash terminal session and see 2
>  entries, starting bash
>  again will give 3 entries.
>  
>  On Fedora, /etc/profile defines a shell function called pathmunge
>  that checks to see if
>  a directory is already in the PATH before adding it to the PATH.  
Ok, I will look into pathmunge, just to learn something new.
thanks a lot for this.


Anil

[Roger Heflin]

Trick is add this around the path add.

If [ $path_add -ne 1 ] ; then
Path addition code
Path_add=1
Fi

That only runs it once.

On Fri, Jun 24, 2022, 4:09 AM Anil F Duggirala <anilduggirala(a)fastmail.fm&gt;
wrote:

>  hello,
>  I would like to change the $PATH environment variable permanently, to
>  be able to execute a program more quickly.
>  I have tried adding a new line: export PATH=$PATH:/my/path , to my
>  .bashrc .
>  When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
>  my directory has been appended twice.
>  I don't know exactly what the "export" command actually does, so I am
>  lost here.
>  thanks for your help.
>  _______________________________________________
>  users mailing list -- users(a)lists.fedoraproject.org
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>

[George N. White III]

On Fri, Jun 24, 2022 at 12:36 PM Roger Heflin <rogerheflin(a)gmail.com&gt; wrote:

>  Trick is add this around the path add.
>
>  If [ $path_add -ne 1 ] ; then
>  Path addition code
>  Path_add=1
>  Fi
>
>  That only runs it once.
>  
This clutters up the environment.   I often encountered weird environment
variables when a
user had problems.  Fedora's  /etc/profile defininition of "pathmunge"
checks to see if the proposed entry
is already present:

pathmunge () {
    case ":${PATH}:" in
        *:"$1":*)
            ;;
        *)
            if [ "$2" = "after" ] ; then
                PATH=$PATH:$1
            else
                PATH=$1:$PATH
            fi
    esac
}

Exercise left to the reader: modify path_munge to only add directories that
actually exist
on the system.

I have seen environments with:

   "some_application_version_N/bin:...:some_application_version_1/bin:..."
or
"...:some_application_version_N-1/bin:...:some_application_version_N/bin:
and user
wonders why the new version seems to be the same as the old version.

Environment modules are handy when you want to choose a version to use on
the
command-line.


>  On Fri, Jun 24, 2022, 4:09 AM Anil F Duggirala <anilduggirala(a)fastmail.fm&gt;
>  wrote:
>
> > hello,
> > I would like to change the $PATH environment variable permanently, to
> > be able to execute a program more quickly.
> > I have tried adding a new line: export PATH=$PATH:/my/path , to my
> > .bashrc .
> > When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
> > my directory has been appended twice.
> > I don't know exactly what the "export" command actually does, so I am
> > lost here.
> > thanks for your help.
> > _______________________________________________
> > users mailing list -- users(a)lists.fedoraproject.org
> > To unsubscribe send an email to users-leave(a)lists.fedoraproject.org
> > Fedora Code of Conduct:
> > https://docs.fedoraproject.org/en-US/project/code-of-conduct/
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> > https://lists.fedoraproject.org/archives/list/[e-mail]
> > Do not reply to spam on the list, report it:
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> >
>  _______________________________________________
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>  

-- 
George N. White III

[Anil F Duggirala]

On Fri, 2022-06-24 at 07:36 -0800, Roger Heflin wrote:
>  Trick is add this around the path add.  
>  
>  If [ $path_add -ne 1 ] ; then
>  Path addition code
>  Path_add=1
>  Fi 
Thanks for this Roger, I will try it and let you know,

[Jon LaBadie]

On Fri, Jun 24, 2022 at 07:36:00AM -0800, Roger Heflin wrote:
> Trick is add this around the path add.
>
> If [ $path_add -ne 1 ] ; then
> Path addition code
> Path_add=1
> Fi
>
> That only runs it once.
>
> On Fri, Jun 24, 2022, 4:09 AM Anil F Duggirala <anilduggirala(a)fastmail.fm&gt;
> wrote:
>
> > hello,
> > I would like to change the $PATH environment variable permanently, to
> > be able to execute a program more quickly.
> > I have tried adding a new line: export PATH=$PATH:/my/path , to my
> > .bashrc .
> > When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
> > my directory has been appended twice.
> > I don't know exactly what the "export" command actually does, so I am
> > lost here.
> > thanks for your help. 
Conceptually similar to Roger's approach, I set an environment
variable "OrigPATH" to the initial PATH then assign PATH based
on OrigPATH.

# save a copy of the original path to modify
export OrigPATH=${OrigPATH:-$PATH}
# adjust PATH from OrigPATH to my tastes
export PATH=$HOME/bin:$OrigPATH:/my/path


-- 
Jon H. LaBadie                  jonfu(a)jgcomp.com

[George N. White III]

On Fri, Jun 24, 2022 at 6:04 PM Jon LaBadie <jonfu(a)jgcomp.com&gt; wrote:

>  On Fri, Jun 24, 2022 at 07:36:00AM -0800, Roger Heflin wrote:
>  >Trick is add this around the path add.
>  >
>  >If [ $path_add -ne 1 ] ; then
>  >Path addition code
>  >Path_add=1
>  >Fi
>  >
>  >That only runs it once.
>  >
>  >On Fri, Jun 24, 2022, 4:09 AM Anil F Duggirala <anilduggirala(a)fastmail.fm
>  >
>  >wrote:
>  >
>  >> hello,
>  >> I would like to change the $PATH environment variable permanently, to
>  >> be able to execute a program more quickly.
>  >> I have tried adding a new line: export PATH=$PATH:/my/path , to my
>  >> .bashrc .
>  >> When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
>  >> my directory has been appended twice.
>  >> I don't know exactly what the "export" command actually does, so I
> am
>  >> lost here.
>  >> thanks for your help.
>
>  Conceptually similar to Roger's approach, I set an environment
>  variable "OrigPATH" to the initial PATH then assign PATH based
>  on OrigPATH.
>
>  # save a copy of the original path to modify
>  export OrigPATH=${OrigPATH:-$PATH}
>  # adjust PATH from OrigPATH to my tastes
>  export PATH=$HOME/bin:$OrigPATH:/my/path
>  
Environment modules preserves the current environment
and then adds or modifies environment variables according
to a "modulefile".  The original has been around for decades,
there is now a lua version. Fedora uses environment modules
when building rpm's that support more than one choice for
supporting libraries.  See:

 % ls /usr/share/modulefiles/mpi
mpich-x86_64  openmpi-x86_64

-- 
George N. White III

[Barry]

>  On 24 Jun 2022, at 16:36, Roger Heflin <rogerheflin(a)gmail.com&gt;
> wrote:
>  
>  
>  Trick is add this around the path add.  
>  
>  If [ $path_add -ne 1 ] ; then
>  Path addition code
>  Path_add=1
>  Fi
>  
>  That only runs it once. 
This is a work around for using ,bashrc when .bash_profile is where this should be done.

Barry

>  
> > On Fri, Jun 24, 2022, 4:09 AM Anil F Duggirala <anilduggirala(a)fastmail.fm&gt;
> wrote:
> > hello,
> > I would like to change the $PATH environment variable permanently, to
> > be able to execute a program more quickly.
> > I have tried adding a new line: export PATH=$PATH:/my/path , to my
> > .bashrc .
> > When I log in again, I see that $PATH is now: $PATH:/my/path/:/my/path,
> > my directory has been appended twice.
> > I don't know exactly what the "export" command actually does, so I am
> > lost here.
> > thanks for your help.
> > _______________________________________________
> > users mailing list -- users(a)lists.fedoraproject.org
> > To unsubscribe send an email to users-leave(a)lists.fedoraproject.org
> > Fedora Code of Conduct:
> https://docs.fedoraproject.org/en-US/project/code-of-conduct/
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives:
> https://lists.fedoraproject.org/archives/list/[e-mail]
> > Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
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>  To unsubscribe send an email to users-leave(a)lists.fedoraproject.org
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[George N. White III]

On Fri, Jun 24, 2022 at 7:28 PM Barry <barry(a)barrys-emacs.org&gt; wrote:

>  On 24 Jun 2022, at 16:36, Roger Heflin <rogerheflin(a)gmail.com&gt; wrote:
>
>  
>  Trick is add this around the path add.
>
>  If [ $path_add -ne 1 ] ; then
>  Path addition code
>  Path_add=1
>  Fi
>
>  That only runs it once.
>
>
>  This is a work around for using ,bashrc when .bash_profile is where this
>  should be done.
>  
I think that advice goes back to a time before modern GUI's.  Now many
users have never
encountered a terminal, and distros vary widely in the use of ~/.bashrc,
~/.bash_profle, and
~/.profile.

On my Fedora 35 box, ~/.bash_profile is:

  ----------------------------------ser
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs
  ---------------------------

Some distros have complicated ~/.bashrc or `/.bash_profile files with a
section devoted to
interactive sessions.   This led to issues where users added settings in
the wrong section.
I often ask users to run a failing command in a terminal where they may see
messages
that their GUI tools hide, but getting different behaviours between GUI and
terminal has
become a problem.

-- 
George N. White III

[Barry]

>  On 25 Jun 2022, at 12:36, George N. White III
> <gnwiii(a)gmail.com&gt; wrote:
>  
>  
> > On Fri, Jun 24, 2022 at 7:28 PM Barry <barry(a)barrys-emacs.org&gt; wrote:
>  
> > 
> >>> On 24 Jun 2022, at 16:36, Roger Heflin <rogerheflin(a)gmail.com&gt; wrote:
> >>> 
> >> 
> >> Trick is add this around the path add.  
> >> 
> >> If [ $path_add -ne 1 ] ; then
> >> Path addition code
> >> Path_add=1
> >> Fi
> >> 
> >> That only runs it once.
> > 
> > This is a work around for using ,bashrc when .bash_profile is where this should be
> done.
>  
>  I think that advice goes back to a time before modern GUI's.  Now many users have
> never 
>  encountered a terminal, and distros vary widely in the use of ~/.bashrc, ~/.bash_profle,
> and 
>  ~/.profile. 

Actually they are fixing the problem of inheriting .bash_profile from the login to
the gui session to running the shell on login mode. So no this is not out of date
advice.

>  
>  On my Fedora 35 box, ~/.bash_profile is:
>  
>    ----------------------------------ser
>  # .bash_profile
>  
>  # Get the aliases and functions
>  if [ -f ~/.bashrc ]; then
>          . ~/.bashrc
>  fi 
That has been required since the beginning of time.

You always source .bashrc in the profile.

The reason that you do not set important things in the .bashrc is that if you do
that you cannot override them from the command line.

For example if you set PATH in .bashrc you cannot then change for any sub shells from the
command line.

Barry

>  
>  # User specific environment and startup programs
>    ---------------------------
>  
>  Some distros have complicated ~/.bashrc or `/.bash_profile files with a section devoted
> to 
>  interactive sessions.   This led to issues where users added settings in the wrong
> section.   
>  I often ask users to run a failing command in a terminal where they may see messages 
>  that their GUI tools hide, but getting different behaviours between GUI and terminal has
>
>  become a problem.
>  
>  -- 
>  George N. White III
>  
>  _______________________________________________
>  users mailing list -- users(a)lists.fedoraproject.org
>  To unsubscribe send an email to users-leave(a)lists.fedoraproject.org
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[Barry]

>  On 24 Jun 2022, at 13:10, Anil F Duggirala
> <anilduggirala(a)fastmail.fm&gt; wrote:
>  
>  hello,
>  I would like to change the $PATH environment variable permanently, to
>  be able to execute a program more quickly.
>  I have tried adding a new line: export PATH=$PATH:/my/path , to my
>  .bashrc . 
See PATH in .bash_profile not .bashrc. Because you want it set once,
not every time a new subprocess starts.

When you start a Terminal it should be setup to start a login shell.

Barry

>  When I log in again, I see that $PATH is now:
> $PATH:/my/path/:/my/path,
>  my directory has been appended twice.
>  I don't know exactly what the "export" command actually does, so I am
>  lost here.
>  thanks for your help.
>  _______________________________________________
>  users mailing list -- users(a)lists.fedoraproject.org
>  To unsubscribe send an email to users-leave(a)lists.fedoraproject.org
>  Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/
>  List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
>  List Archives:
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