I have a situation where I have a host machine where I need certain applications installed with side by side versions. Obviously only one can get added to the exports to run by default. As an example we might say it's Python 2.7, Python 3.5, & Python 3.7.
I need to be able to establish an SSH connection to the host, where each connection can set the correct path for the specific version that is required. Is there an easy way to do this. The key here is that each connection cannot affect either the host itself or other connections. Someone running on the host itself shouldn't break because the path was updated by a remote connection.
For the case of multiple (python and other) hierarchies, and assuming that the tools are invokes by the tool name (python ...), prepending the preferred path to the system path will provide a way to specify per-instance tool setting, without having side effect between jobs.
ssh ... 'PATH=/path/to/python3.1/bin:$PATH command'
Depending on the number of tools, and complexity of the setup, you might want to implement this as a wrapper
ssh ... '/path/to/run-with-pkgs python-3.2 pkg2 -- command'
With the pkg-setup script source various config script. Something along the lines of:
run-with-pkgs
#! /bin/bash
while [ $# -gt 0 ] && [ "$1" != "--" ] ; do
source "/path/to/setup.d/$1.sh"
shift
done
if [ "$1" = "--" ] ; then
shift
exec "$#"
fi
Related
My /etc/bash.bashrc contains this code by default (Git for Windows)
# If started from sshd, make sure profile is sourced
if [[ -n "$SSH_CONNECTION" ]] && [[ "$PATH" != *:/usr/bin* ]]; then
. /etc/profile
fi
I know it is documented, but I still don't understand what it means. I set an echo "here" inside of the if to see if it ever runs, but I can't make it. What exactly does this mean, and what even is an sshd? Or did I accidentally just type "d" on my keyboard and its a typo?
https://www.ssh.com/ssh/sshd/
sshd is the OpenSSH server process. It listens to incoming connections using the SSH protocol and acts as the server for the protocol. It handles user authentication, encryption, terminal connections, file transfers, and tunneling.
That code checks if the $SSH_CONNECTION environment variable is set to see if the shell was started by sshd. If so, and $PATH does not contain /usr/bin, then it executes the commands in /etc/profile in the current shell context.
Is there a way for a shell script to determine if it is called from a terminal in a virtual machine running Ubuntu, or a W10 terminal using the bash call (installed Ubuntu app in W10)?
I am working in both environments and have a lot of useful shell scripts to make my work more efficient on the virtual machine, e.g. opening specific URLs or running sets of commands. I would like them to work on the Windows side as well. However, my scripts sets up directories which will have to be different on my Windows side.
I have installed the ubuntu app from Windows Store, which allows me to open a bash window and source the files. I could just check if ~ returns an empty string, but is there a more robust way of doing it?
I am running Windows 10, version 17763 and using Ubuntu 18.04 LTS.
E.g.
C:\.sourceThis.sh
#!/bin/bash
myDir="/home/user/stuff"
cdMySub() {
cd "$myDir/$1"
}
I can run this in a Windows terminal by
C:\> bash
USER#XXXX:/mnt/c/$ source ./.sourceThis.sh
USER#XXXX:/mnt/c/$ cdMySub someSubDirectoryName
-bash: cd: /home/user/stuff/someSubDirectoryname: No such file or directory
USER#XXXX:/mnt/c/$ #Fail!
but it does not work, since the Ubuntu file system is different to Windows.
I would like to change .sourceThis.sh to something like
...
if [[ "Something that detects virtual machine" ]] ; then
myDir="/home/user/stuff"
elif [[ "Something that detects 'bash' from Windows prompt" ]] ; then
myDir="/mnt/c/user/stuff"
fi
so that the outcome is instead
C:\> bash
USER#XXXX:/mnt/c/$ source ./.sourceThis.sh
USER#XXXX:/mnt/c/$ cdMySub someSubDirectoryName
USER#XXXX:/mnt/c/stuff/someSubDirectoryName$ #Yeay, success!
EDIT:
I cannot just check for the validity of the default directory, since the scripts create the directory if it does not exist. I want it to point to another default path instead.
I use different user names, so I could check that the output from ~ is the "Windows or VM user".
USER#XXXX:/mnt/c$ echo ~
/home/USER
Thus,
tmpHome=~
if [[ "${tmpHome##*/}" == "USER" ]] ; then
# Windows user
elif [[ "${tmpHome##*/}" == "VM" ]] ; then
# VM user
fi
works for my specific user. However, I suspect that I want to use this on different users (e.g. share it with a colleague). This demands a more robust way.
I am not too experience with Linux. I do not know how to navigate the world of users, processes and tasks, which I suspect can give the answer.
I have used this for a long time successfully:
if [[ "$(uname -r)" == *Microsoft ]]; then
do stuff
fi
You could always use an if condition checking whether the path exists, and run the script from there :
if [[ -f /home/user/stuff ]]; do
script if running on linux
else
script if running on windows
fi
Here the -f flags is a bash condition checking whether the file at specified path exists, returns true if it does. You can add other validations to check whether the file also exists when running on Windows and whatnot.
Bash provides information about the system that is running it it the MACHTYPE, HOSTTYPE, and OSTYPE built-in variables.
Example values for a physical Linux system are:
MACHTYPE=x86_64-redhat-linux-gnu
HOSTTYPE=x86_64
OSTYPE=linux-gnu
Example values for a WSL Linux system are:
MACHTYPE=x86_64-pc-linux-gnu
HOSTTYPE=x86_64
OSTYPE=linux-gnu
One possible way to check if the system is WSL Linux is:
if [[ $MACHTYPE == *-pc-* ]]; then
...
fi
#Dexirian and #Michael Hoffman suggested a method that worked!
For me uname -r returns x.x.x-17763-Microsoft from the Windows prompt and x.x.x-xx-generic on my virtual machine.
Thus,
if [[ "$(uname -r)" =~ "Microsoft" ]] ; then
myDir="/mnt/c/user/stuff"
elseif [[ "$(uname -r)" =~ "generic" ]] ; then
myDir="/home/user/stuff"
fi
works like a charm!
I am facing an issue using environment variables in my service script.
In my services script, i am using an environmental variable i.e. INSTALL_DIR whose value may vary on different system. I have to get the installation directory from $INSTALL_DIR and then i have to start the service. when i am running the service script the environment variable is not sourced at all.
Is it possible to source the installation directory from INSTALL_DIR environment variable. another option i can think is dynamically creating the service script using INSTALL_DIR environment variable.
echo "INSTALL DIR: ${INSTALL_DIR}"
name=`basename $0`
pid_file="/var/run/$name.pid"
get_pid() {
cat "$pid_file"
}
is_running() {
[ -f "$pid_file" ] && ps `get_pid` > /dev/null 2>&1
}
Start()
{
echo "Starting Application"
if is_running; then
echo "[`get_pid`] Already Started"
else
if [ -z "$user" ]; then
nohup $INSTALL_DIR/bin/application 2>&1 &
else
nohup sudo -u "$user" $cmd 1> $INSTALL_DIR/bin/application 2>&1 &
fi
echo $! > "$pid_file"
if ! is_running; then
echo "Unable to start, see logs"
exit 1
fi
echo "[`get_pid`] Started"
fi
}
I am trying to run the application using following command
service application start
In my services script ... I have to get the installation directory from $INSTALL_DIR and then i have to start the service.
Your question isn't really about shell scripting, but about your system's startup. Unfortunately that process varies by Linux distribution, and tends to be poorly documented.
For example, man service says, service runs a System V init script or upstart job in as predictable an environment as possible, removing most environment variables and with the current working directory set to /., but man upstart says:
$ man -k upstart
upstart: nothing appropriate.
Not only that, but the service manpage specifically lists the environment variables a script will start with. Needless to say, yours isn't among them.
The traditional approach to parameterizing startup scripts is to put the information in a known file, normally in /etc, and reference that file in the script. In your case, you could do something like:
INSTALL_DIR=$(cat /etc/my-install-dir.cfg)
and then proceed accordingly.
There might be ways to coerce your startup to support other environment variables. But, sooner or later, the information you need has to be stored somewhere on the filesystem. It seems to me the simplest approach is to reserve a filename to hold that information, and read that file directly.
Use this below code in your script.
if [[ -z "${INSTALL_DIR}" ]]; then
echo "INSTALL_DIR is undefined"
else
INSTALL_DIR=<<your installation directory>>
fi
I am trying to login on one of the remote server(Box1) and trying to read one file on remote server(Box1).
That contain the another server(Box2) details, base upon that details I have to come back to the local server and ssh to another server(Box2) for some data crunching. and so on.....
ssh box1.com << EOF
if [[ ! -f /home/rakesh/tomar.log ]]
then
echo "LOG file not found"
else
echo " LOG file present"
export server_node1= `cat /home/rakesh/tomar.log`
fi
EOF
ssh box2.com << EOF
if [[ ! -f /home/rakesh/tomar.log ]]
then
echo "LOG file not found"
else
echo " LOG file present"
export server_node2= `cat /home/rakesh/tomar.log`
fi
EOF
but I am not getting value of "server_node1" and "server_node2" on local machine.
any help would be appreciated.
Just like bash -c 'export foo=bar' cannot declare a variable in the calling shell where you typed this, an ssh command cannot declare a variable in the calling shell. You will have to refactor so that the calling shell receives the information and knows what to do with it.
I agree with the comment that storing a log file in a variable is probably not a sane, or at least elegant, thing to do, but the easy way to do what you are attempting is to put the ssh inside the assignment.
server_node1=$(ssh box1.com cat tomar.log)
server_node2=$(ssh box2.com cat tomar.log)
A few notes and amplifications:
The remote shell will run in your home directory, so I took it out (on the assumption that /home/rt9419 is your home directory, obviously).
In case of an error in the cat command, the exit code of ssh will be the error code from cat, and the error message on standard error will be visible on your standard error, so the echo seemed quite superfluous. (If you want a custom message, variable=$(ssh whatever) || echo "Custom message" >&2 would do that. Note the redirection to standard error; it doesn't seem to matter here, but it's good form.)
If you really wanted to, you could run an arbitrarily complex command in the ssh; as outlined above, it didn't seem necessary here, but you could do assigment=$(ssh remote 'if [[ things ]]; then for variable in $(complex commands to drive a loop); do : etc etc; done; fi; more </dev/null; exit "$variable"') or whatever.
As further comments on your original attempt,
The backticks in the here document in your attempt would be evaluated by your local shell before the ssh command even ran. There are separate questions about how to fix that; see e.g. How have both local and remote variable inside an SSH command. but in short, unless you absolutely require the local shell to be able to modify the commands you send, probably put them in single quotes, like I did in the silly complex ssh example above.
The function of export is to make variables visible to child processes. There is no way to affect the environment of a parent process (short of having it cooperate and/or coordinate the change, as in the code above). As an example to illustrate the difference, if you set PERL5LIB to a directory with Perl libraries, but fail to export it, the Perl process you start will not see the variable; it is only visible to the current shell. When you export it, any Perl process you start as a child of this shell will also see this variable and the value you assigned. In other words, you export variables which are not private to the current shell (and don't export private ones; aside from making sure they are private, this saves the amount of memory which needs to be copied between processes), but that still only makes them visible to children, by the design of the U*x process architecture.
You should get back the file from box1and box2 with an scp:
scp box1.com:/home/rt9419/tomar.log ~/tomar1.log
#then you can cat!
export server_node1=`cat ~/tomar1.log`
idem with box2
scp box2.com:/home/rt9419/tomar.log ~/tomar2.log
#then you can cat!
export server_node2=`cat ~/tomar2.log`
There are several possibilities. In your case, you could on the remote system create a file (in bash syntax), containing the assignments of these variables, for example
echo "export server_node2='$(</home/rt9419/tomar.log)'" >>export_settings
(which makes me wonder why you want the whole content of your logfile be stored into a variable, but this is another question), then transfer this file to your host (for example with scp) and source it from within your bash script.
Recently I wrote a script which sets an environment variable, take a look:
#!/bin/bash
echo "Pass a path:"
read path
echo $path
defaultPath=/home/$(whoami)/Desktop
if [ -n "$path" ]; then
export my_var=$path
else
echo "Path is empty! Exporting default path ..."
export my_var=$defaultPath
fi
echo "Exported path: $my_var"
It works just great but the problem is that my_var is available just locally, I mean in console window where I ran the script.
How to write a script which allow me to export global environment variable which can be seen everywhere?
Just run your shell script preceded by "." (dot space).
This causes the script to run the instructions in the original shell. Thus the variables still exist after the script finish
Ex:
cat setmyvar.sh
export myvar=exists
. ./setmyvar.sh
echo $myvar
exists
Each and every shell has its own environment. There's no Universal environment that will magically appear in all console windows. An environment variable created in one shell cannot be accessed in another shell.
It's even more restrictive. If one shell spawns a subshell, that subshell has access to the parent's environment variables, but if that subshell creates an environment variable, it's not accessible in the parent shell.
If all of your shells need access to the same set of variables, you can create a startup file that will set them for you. This is done in BASH via the $HOME/.bash_profile file (or through $HOME/.profile if $HOME/.bash_profile doesn't exist) or through $HOME/.bashrc. Other shells have their own set of startup files. One is used for logins, and one is used for shells spawned without logins (and, as with bash, a third for non-interactive shells). See the manpage to learn exactly what startup scripts are used and what order they're executed).
You can try using shared memory, but I believe that only works while processes are running, so even if you figured out a way to set a piece of shared memory, it would go away as soon as that command is finished. (I've rarely used shared memory except for named pipes). Otherwise, there's really no way to set an environment variable in one shell and have another shell automatically pick it up. You can try using named pipes or writing that environment variable to a file for other shells to pick it up.
Imagine the problems that could happen if someone could change the environment of one shell without my knowledge.
Actually I found an way to achieve this (which in my case was to use a bash script to set a number of security credentials)
I just call bash from inside the script and the spawned shell now has the export values
export API_USERNAME=abc
export API_PASSWORD=bbbb
bash
now calling the file using ~/.app-x-setup.sh will give me an interactive shell with those environment values setup
The following were extracted from 2nd paragraph from David W.'s answer: "If one shell spawns a subshell, that subshell has access to the parent's environment variables, but if that subshell creates an environment variable, it's not accessible in the parent shell."
In case a user need to let parent shell access your new environment variables, just issue the following command in parent shell:
source <your_subshell_script>
or using shortcut
. <your_subshell_script>
You got to add the variable in your .profile located in /home/$USER/.profile
Yo can do that with this command:
echo 'TEST="hi"' >> $HOME/.profile
Or by edit the file with emacs, for example.
If you want to set this variable for all users, you got to edit /etc/profile (root)
There is no global environment, really, in UNIX.
Each process has an environment, originally inherited from the parent, but it is local to the process after the initial creation.
You can only modify your own, unless you go digging around in the process using a debugger.
write it to a temporary file, lets say ~/.myglobalvar and read it from anywhere
echo "$myglobal" > ~/.myglobalvar
Environment variables are always "local" to process execution the export command allow to set environment variables for sub processes. You can look at .bashrc to set environment variables at the start of a bash shell. What you are trying to do seems not possible as a process cannot modify (or access ?) to environment variables of another process.
You can update the ~/.bashrc or ~/.bash_profile file which is used to initialize the environment.
Take a look at the loading behavior of your shell (explained in the manpage, usually referring to .XXXshrc or .profile). Some configuration files are loaded at login time of an interactive shell, some are loaded each time you run a shell. Placing your variable in the latter might result in the behavior you want, e.g. always having the variable set using that distinct shell (for example bash).
If you need to dynamically set and reference environment variables in shell scripts, there is a work around. Judge for yourself whether is worth doing, but here it is.
The strategy involves having a 'set' script which dynamically writes a 'load' script, which has code to set and export an environment variable. The 'load' script is then executed periodically by other scripts which need to reference the variable. BTW, the same strategy could be done by writing and reading a file instead of a variable.
Here's a quick example...
Set_Load_PROCESSING_SIGNAL.sh
#!/bin/bash
PROCESSING_SIGNAL_SCRIPT=./Load_PROCESSING_SIGNAL.sh
echo "#!/bin/bash" > $PROCESSING_SIGNAL_SCRIPT
echo "export PROCESSING_SIGNAL=$1" >> $PROCESSING_SIGNAL_SCRIPT
chmod ug+rwx $PROCESSING_SIGNAL_SCRIPT
Load_PROCESSING_SIGNAL.sh (this gets dynamically created when the above is run)
#!/bin/bash
export PROCESSING_SIGNAL=1
You can test this with
Test_PROCESSING_SIGNAL.sh
#!/bin/bash
PROCESSING_SIGNAL_SCRIPT=./Load_PROCESSING_SIGNAL.sh
N=1
LIM=100
while [ $N -le $LIM ]
do
# DO WHATEVER LOOP PROCESSING IS NEEDED
echo "N = $N"
sleep 5
N=$(( $N + 1 ))
# CHECK PROCESSING_SIGNAL
source $PROCESSING_SIGNAL_SCRIPT
if [[ $PROCESSING_SIGNAL -eq 0 ]]; then
# Write log info indicating that the signal to stop processing was detected
# Write out all relevent info
# Send an alert email of this too
# Then exit
echo "Detected PROCESSING_SIGNAL for all stop. Exiting..."
exit 1
fi
done
~/.bin/SOURCED/lazy script to save and load data as flat files for system.
[ ! -d ~/.megadata ] && mkdir ~/.megadata
function save_data {
[ -z "$1" -o -z "$2" ] && echo 'save_data [:id:] [:data:]' && return
local overwrite=${3-false}
[ "$overwrite" = 'true' ] && echo "$2" > ~/.megadata/$1 && return
[ ! -f ~/.megadata/$1 ] && echo "$2" > ~/.megadata/$1 || echo ID TAKEN set third param to true to overwrite
}
save_data computer engine
cat ~/.megadata/computer
save_data computer engine
save_data computer megaengine true
function get_data {
[ -z "$1" -o -f $1 ] && echo 'get_data [:id:]' && return
[ -f ~/.megadata/$1 ] && cat ~/.megadata/$1 || echo ID NOT FOUND
:
}
get_data computer
get_data computer
Maybe a little off topic, but when you really need it to set it temporarily to execute some script and ended up here looking for answers:
If you need to run a script with certain environment variables that you don't need to keep after execution you could do something like this:
#!/usr/bin/env sh
export XDEBUG_SESSION=$(hostname);echo "running with xdebug: $XDEBUG_SESSION";$#
In my example I just use XDEBUG_SESSION with a hostname, but you can use multiple variables. Keep them separated with a semi-colon. Execution as follows (assuming you called the script debug.sh and placed it in the same directory as your php script):
$ debug.sh php yourscript.php