I have a program, let's call it exampleProg, in my /opt directory, and I want to run it from any directory, rather than just:
/opt/radFolder/exampleProg
This should be a simple task, I've done it several times before on different computers. I've searched around, and found instructions ranging from:
edit .bash
edit .bashrc
edit .profile (Another stackoverflow answer said that, while this worked at one time, it no longer functions.)
edit /etc/environment/
with PATH="$HOME/bin:$PATH:/opt/radFolder/:" or just adding the /opt/radFolder bit.
Yet none of them seem to work. The problem that I'm running into is that there doesn't seem to be a yet there doesn't seem to be a universally agreed-upon solution. I've tried so many that I think one of my changes has prevented the appropriate one from taking effect. Would someone help me put this to rest once and for all? Many thanks in advance.
I'm running ubuntu 14.04 LTS x64.
First, understand that writing things to those files does not mean everything is instantaneously, and globally, changed. In fact, nothing is changed until the file is sourced (via . or source), and even then, the environment changes apply only to the current shell (and subsequent created children, if export is used).
INVOCATION, near the top of man bash, spells out which files are automatically sourced when. To summarize:
~/.bashrc is read for new non-login, interactive shells, e.g., when you open a GUI terminal. On many systems, this file by default in turn sources /etc/bashrc.
/etc/profile, ~/.bash_profile, and ~/.profile are read by interactive login shells.
Adding to ~/.bashrc should be effective, but it will only work for subsequently invoked, interactive, non-login shells (and their children, if $PATH is exported). However, since it's prone to being sourced repeatedly, using it to add to an existing variable (as with $PATH) can produce repeated concatenations (see here).
An issue with the second category, .profile, is that if you use a GUI login, the display manager may not source it, but it logs you in, meaning, you never invoke a login shell and hence none of those is ever sourced. If this is the case, sourcing them from ~/.xsession should work (this has a system wide correlate in /etc/X11).
Related
EDIT
The answer to my question is actually obvious, I simply forgot about the meaning of the EXPORT keyword. I still drop the explanation here, just in case.
So in a few words, when opening a terminal with Ctrl-Alt T a new shell is created, which is a child of the shell created at loggin. As explained here, the loggin shell is initialized by reading /etc/profile, and as explained here and more specifically here elements of the environment are transmitted to child processes, notably variables prefixed with the EXPORT keyword.
I am trying to understand what is the mechanism under which the PATH is set under linux when opening a new (virtual) terminal.
I know one can change the PATH in several files (e.g. system : /etc/{profile, bash.bashrc, ... } or user: ~/{.profile, .bash_login, .bashrc... }, some of which are read at login, the others when opening new (virtual) terminals.
According to my tests, it seems the "profile" files are read at startup (when the user logs in), which registers some startup values for variables such as PATH. Then, each time a terminal is opened these startup values are provided to other script (e.g. bashrc) for further configuration, resulting in something like : PATH_IN_TERMINAL=$BASHRC_ADDONS:$PATH_FROM_PROFILE
Notably, ~/.profile won't normally be read after login. Changing this file won't have any effect in the current session and the PATH_FROM_PROFILE part of the PATH will remain the same until one logs in again (after logout or through ssh connection for instance).
Am I correct ? And if so, where can I find a doc on the subject ?
Thanks
This is the best explanation I have found on the subject: Startup Files
The simple explanation, in most common situations is:
Upon initial login to host, read /etc/profile followed by the first of
~/.bash_profile, ~/.bash_login or ~/.profile. ~/.profile is
supported by multiple shells, so is preferred.
When Bash starts, but not immediately after login, read ~/.bashrc.
So, profile files are intended to run upon login and should be used to print initial messages (e.g. Security Warning, Message of the Day), check mail, and configure settings/variables that rarely change. Either system-wide (quotas, MOTD, etc.), or user-specific (timezone, locale, terminal, etc.).
.bashrc files are intended for individual users to customize their interactive experience. e.g. defining aliases, setting prompts, adding to PATH, etc.
I almost always add source ~/.bashrc to the end of my .profile file so that my shell is always customized to my requirements, even immediately after login.
NOTE: The above only applies to interactive shells (e.g. running on a terminal). None of these files are read if bash is run non-interactively (e.g. via cron). In those cases, you should create a different file containing required variables and specify that via the BASH_ENV environment file.
In a graphical DE, like KDE, what command can be used to add a new environment variable that can be used by any other process?
Note:
1) I'm aware of export A=B, but it only works for subsequent processes started in the same shell that executed the export, processes started else where, like a graphical application such as Chrome, won't be aware of the export.
2) I'm also aware that you can put it into ~/.bash_profile or alike, but that would need a restart/relogin for the setting to take effect.
Is there something like export but have effect for all applications and doesn't require a significant restart?
Your assumption that you need to restart after placing a variable definition (whether through an export statement or otherwise) in ~/.bash_profile, is flawed. You only need to source the file again after making modifications:
source ~/.bash_profile
or the more portable version:
. ~/.bash_profile
Either statement will (re)load any definitions in that file into your current shell. Sourcing is not the same as executing the script: it will modify the environment in the calling shell itself, not a subshell running the script.
A file like ~/.bash_profile may have many other definitions and settings in it that will mess with the shell. It is better to create a small (temporary) snippet with just the variables you want, and source that instead, as #JeremiahMegel suggests.
If you want to change the environment for a single process you run from the command line, you can set the variables on the same command line:
VAR=value /usr/bin/gedit
This will run gedit with the environment variable VAR set to value, but only for that one child process.
Unfortunately, your desktop applications are a bit more static than that. Most of the graphical applications you see in the menus are probably going to be represented by .desktop files in a folder like /usr/share/applications. These files are run in an environment that has almost none of the variables you are expecting. They rely on absolute paths, and most of the configuration is done by pointing the .desktop file to a script that performs its own setup. You can modify some of these files on an individual basis if you absolutely have to, but I would not recommend doing that. If you do insist on messing around with the graphical apps on your desktop, I would recommend making a copy of the desktop files you plan to modify in to ~/.local/share/applications, or whatever the equivalent is on your system. Those files will override anything found in /usr/share/applications and will only affect you.
We have put together a perl script that essentially looks at the argument that is being passed to it checks if is creating or modifying a file then it saves that in a mysql database so that it is easily accessible later. Here is the interesting part, how do I make this perl script run before all of the commands typed in the terminal. I need to make this dummy proof so people don't forget to run it.
Sorry I didn't formulate this question properly. What I want to do is prepend to each command such that each command will run like so "./run.pl ls" for example. That way I can track file changes if the command is mv or it creates an out file for example. The script pretty much takes care of that but I just don't know how to run it seamlessly to the user.
I am running ubuntu server with the bash terminal.
Thanks
If I understood correctly you need to execute a function before running every command, something similar to preexec and precmd in zsh.
Unfortunately bash doesn't have a native support for this but you can do it using DEBUG trap.
Here is a sample code applying this method.
This page also provide some useful information.
You can modify the ~/.bashrc file and launch your script there. Do note that each user would (and should) still have the privelege to modify this file, potentially removing the script invocation.
The /etc/bash.bashrc file is system-wide and only changeable by root.
These .bashrcs are executed when a new instance of bash is created (e.g. new terminal).
It is not the same as sh, the system shell, that is dash on Ubuntu systems.
After I make changes in .bash_rc or .bash_profile, when I start GNU screen, it doesn't recognize those changes.
I can
source ~/.bash_profile
and it works for the current screen window I have open, but I have to do that for every screen window I have open.
How do I get screen to read my latest changes in my bash configuration?
If you want screen to always treat your shell as a login shell, and source the same files that would be read if just started a new shell normally, add the following to ~/.screenrc (or maybe ~/.byobu/.screenrc, as pointed out in the comment):
shell -$SHELL
This way, you don't need to manually tell it to source your files each time you start a new screen. Though you would have to if you just made changes and wanted those changes to be reflected in your current screen.
The documentation for this (and lots of other screen details) can be found here. Basically, shell is a command to screen telling it to run the following when it needs to create a new shell. $SHELL is the usual variable holding the path to your preferred shell. And the dash - in front of $SHELL indicates that it should be run as a login shell (which will typically mean it sources your ~/.bash_profile, etc.).
It's worth pointing out, however, that screen defaults to just inheriting most environment variables from the shell where you start screen; and a login sub-shell may alter some environment variables in unexpected ways. I ran into a situation where elements of my $PATH were basically permuted. I solved the problem thanks to this particularly excellent answer on superuser.
You may notice the source command available. It's important to note that this sources a file of screen commands, rather than shell commands. Other relevant (screen) commands include eval and exec.
You have to do it in each screen that you have open since they are all different shells. If you need the change every time a new shell is opened, I suggest you put the changes in ~/.bashrc instead.
Apparently, you can send a command to all windows at once using this syntax:
C-a :
at "#" stuff "source ~/.bash_profile^M"
I have some directories with a number of "hidden" files. One example of this is I'm in a source controlled sandbox and some of the files have not been checked out yet.
When I hit TAB, I'd like the option of seeing these files.
A similar question has been asked before: CVS Tab completion for modules under linux
The answers to that question summarize to: "Ubuntu's got that built in".
I don't have the option of switching to Ubuntu, but surely I can use the same mechanisms.
how can I hook into the TAB-completion feature of tcsh to add additional file Support for CVS, SVN and BitKeeper would all be useful.
More important than support for a specific source control system is the ability to control the returned list myself.
An acceptable solution would also be to use a key-binding other than TAB. (ctrl- perhaps)
From the manpage:
the complete builtin command can be used to tell the shell how to complete words other than filenames, commands and variables
might get you started
I do not know how to program in tcsh. But if you can, then you could look at the file named "bash_completion" from the archive (find the download link here.)
On line 1673 begins CVS completion code - and this might be portable to csh if you are familiar with the differences between bash/tcsh.
On my ubuntu machine, there is also a section for SVN completion (in /etc/bash_completion) that doesn't seem to be present in the maintainer's archive.
That's not Ubuntu-specific behavior, it's the bash-completion project.
You could use that, if you can switch from tcsh to bash.