This question already has answers here:
How to get the default shell
(5 answers)
Closed 6 years ago.
I am composing a bash script to serve as a utility tools.
The challenges I am facing now is:
- user using my tool will be running in bash environment
- however, some of them might default using krcsh or tcsh. they might have aliases or configurations set in there.
So, I need to prompt/guide user to resolve this during installation. My first challenge: How am I suppose to know the user's default shell within my install.sh?
Knowing the "default" shell, I can prompt and guide the user to do necessary transfer to bash.
my testing code:
my result:
1/ is fault obviously. It return the current shell which is my install.sh (bash)
2/ I am doubtful. It seems to be the history of what I have run before. It does not show me my default configured shell. My case, my terminal default shell is bash, and I run tsch for testing purpose. So the script parsed wrong information and will though my default shell is tcsh. It will then assist me to port configurations from tcsh to bash during the installation process.
If you want to check the shell you are using, you can use the following methods:
echo $0 in terminal will show you the program running if you want to check the shell you are currently using.
echo $SHELL - with this command you can read the user's default shell in the terminal you are running.
If you want to prompt, easily you can put the echo $SHELL in the part of your script where you need to show the current shell you are using.
Don't forget to put #!/bin/bash if your script is designed to run in a bash shell!
Related
Closed. This question is off-topic. It is not currently accepting answers.
Want to improve this question? Update the question so it's on-topic for Stack Overflow.
Closed 10 years ago.
Improve this question
I have a command that runs fine if I ssh to a machine and run it, but fails when I try to run it using a remote ssh command like :
ssh user#IP <command>
Comparing the output of "env" using both methods resutls in different environments. When I manually login to the machine and run env, I get much more environment variables then when I run :
ssh user#IP "env"
Any idea why ?
There are different types of shells. The SSH command execution shell is a non-interactive shell, whereas your normal shell is either a login shell or an interactive shell. Description follows, from man bash:
A login shell is one whose first character of argument
zero is a -, or one started with the --login option.
An interactive shell is one started without non-option
arguments and without the -c option whose standard input
and error are both connected to terminals (as determined
by isatty(3)), or one started with the -i option. PS1 is
set and $- includes i if bash is interactive, allowing a
shell script or a startup file to test this state.
The following paragraphs describe how bash executes its
startup files. If any of the files exist but cannot be
read, bash reports an error. Tildes are expanded in file
names as described below under Tilde Expansion in the
EXPANSION section.
When bash is invoked as an interactive login shell, or as
a non-interactive shell with the --login option, it first
reads and executes commands from the file /etc/profile, if
that file exists. After reading that file, it looks for
~/.bash_profile, ~/.bash_login, and ~/.profile, in that
order, and reads and executes commands from the first one
that exists and is readable. The --noprofile option may
be used when the shell is started to inhibit this behav
ior.
When a login shell exits, bash reads and executes commands
from the file ~/.bash_logout, if it exists.
When an interactive shell that is not a login shell is
started, bash reads and executes commands from ~/.bashrc,
if that file exists. This may be inhibited by using the
--norc option. The --rcfile file option will force bash
to read and execute commands from file instead of
~/.bashrc.
When bash is started non-interactively, to run a shell
script, for example, it looks for the variable BASH_ENV in
the environment, expands its value if it appears there,
and uses the expanded value as the name of a file to read
and execute. Bash behaves as if the following command
were executed:
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the PATH variable is not used to search
for the file name.
How about sourcing the profile before running the command?
ssh user#host "source /etc/profile; /path/script.sh"
You might find it best to change that to ~/.bash_profile, ~/.bashrc, or whatever.
(As here (linuxquestions.org))
Shell environment does not load when running remote ssh command. You can edit ssh environment file:
vi ~/.ssh/environment
Its format is:
VAR1=VALUE1
VAR2=VALUE2
Also, check sshd configuration for PermitUserEnvironment=yes option.
I had similar issue, but in the end I found out that ~/.bashrc was all I needed.
However, in Ubuntu, I had to comment the line that stops processing ~/.bashrc :
#If not running interactively, don't do anything
[ -z "$PS1" ] && return
I found an easy resolution for this issue was to add
source /etc/profile
to the top of the script.sh file I was trying to run on the target system.
On the systems here, this caused the environmental variables which were needed by script.sh to be configured as if running from a login shell.
In one of the prior responses it was suggested that ~/.bashr_profile etc... be used.
I didn't spend much time on this but, the problem with this is if you ssh to a different user on the target system than the shell on the source system from which you log in it appeared to me that this causes the source system user name to be used for the ~.
Just export the environment variables you want above the check for a non-interactive shell in ~/.bashrc.
This question already has answers here:
Global environment variables in a shell script
(7 answers)
Closed 2 years ago.
I have a seemingly simple bash script to setup my environment:
The first two lines are:
#!/bin/bash
export CVE_ENV_DIR=$PWD
easy, hey? Well, see what happens when I run it, I get the following output:
$ echo $PWD
/work/env
$ ./env.sh
$ echo $CVE_ENV_DIR
$
Why does CVE_ENV_DIR not get set to /work/env? What is happening here? When I type export CVE_ENV_DIR=$PWD manually on the shell, it works as expected...
Child shells cannot affect the environment of their parent. If you want the script to affect the parent's environment, you need to:
source ./env.sh
So what's going on? When you run a bash script, either by bash env.sh or env.sh, you're spawning a program with its own environment, an environment that's divorced from its parent. But, when you run the commands contained in the script at the command line, or using source, there is no spawned environment.
Edit to address #syme's comment. Bash scripts meant to be read using source are often pure configuration, containing only assignments and calculations. It's possible to also make them a little more helpful and self-documenting with a clever she-bang hack like:
#!/bin/echo USAGE: source
# Default configuration file for the Frobnicator package.
FOO=bar
BAR=$(stat /baz)
[[ -f /baz ]] && BAZ=file || BAZ=
export FOO BAR BAZ
Making a bash script meant for configuration look like a configuration script, you help future maintainers. You also help yourself my modularizing your script code into distinct parts, each part with its one unique function.
As a side note, please don't export on the same line as you assign.
This question already has answers here:
Can I export a variable to the environment from a Bash script without sourcing it?
(13 answers)
Closed 3 years ago.
I have created a virtual environment on my debian system and i made a script that activates it (should).
However when i execute the script nothing shows up, not even an error, my guess is that it is running in a different shell or something but I don't know how to solve it.
Here is the code of the script
#!/bin/bash
source ~/PythonEnv/environments/my_env/bin/activate
I have changed the permissions already with chmod u+x, so that is not a problem.
When i execute the script nothing shows up at all. Any thoughts???
Add set -x at the beginning of your bash script will do the trick.
-x Print commands and their arguments as they are executed.
You can see more bash options here
http://linuxcommand.org/lc3_man_pages/seth.html
Adding x-permissions is not necessary, since you are using source with an absolute path. Of course this sets the environment only which is executed by the shell script which you have posted here. If you want the changes in your interactive shell, it is pointless to do it inside a script. You have to source the activate script in your shell (respectively inside that process where you want the environment to be modified).
When creating Bash scripts, I have always had a line right at the start defining the PATH environment variable. I recently discovered that this doesn't make the script very portable as the PATH variable is different for different versions of Linux (in my case, I moved the script from Arch Linux to Ubuntu and received errors as various executables weren't in the same places).
Is it possible to copy the PATH environment variable defined by the login shell into the current Bash script?
EDIT:
I see that my question has caused some confusion resulting in some thinking that I want to change the PATH environment variable of the login shell with a bash script, which is the exact opposite of what I want.
This is what I currently have at the top of one of my Bash scripts:
#!/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
# Test if an internet connection is present
wget -O /dev/null google.com
I want to replace that second line with something that copies the value of PATH from the login shell into the script environment:
#!/bin/bash
PATH=$(command that copies value of PATH from login shell)
# Test if an internet connection is present
wget -O /dev/null google.com
EDIT 2: Sorry for the big omission on my part. I forgot to mention that the scripts in question are being run on a schedule through cron. Cron creates it's own environment for running the scripts which does not use the environment variables of the login shell or modify them. I just tried running the following script in cron:
#!/bin/bash
echo $PATH >> /home/user/output.txt
The result is as follows. As you can see, the PATH variable used by cron is different to the login shell:
user#ubuntu_router:~$ cat output.txt
/usr/bin:/bin
user#ubuntu_router:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
Don't touch the user's PATH at all unless you have a specific reason. Not doing anything will (basically) accomplish what you ask.
You don't have to do anything to get the user's normal PATH since every process inherits the PATH and all other environment variables automatically.
If you need to add something nonstandard to the PATH, the usual approach is to prepend (or append) the new directory to the user's existing PATH, like so:
PATH=/opt/your/random/dir:$PATH
The environment of cron jobs is pretty close to the system's "default" (for some definition of "default") though interactive shells may generally run with a less constrained environment. But again, the fix for that is to add any missing directories to the current value at the beginning of the script. Adding directories which don't exist on this particular system is harmless, as is introducing duplicate directories.
I've managed to find the answer to my question:
PATH=$PATH:$(sed -n '/PATH=/s/^.*=// ; s/\"//gp' '/etc/environment')
This command will grab the value assigned to PATH by Linux from the environment file and append it to the PATH used by Cron.
I used the following resources to help find the answer:
How to grep for contents after pattern?
https://help.ubuntu.com/community/EnvironmentVariables#System-wide_environment_variables
This question already has answers here:
Pass commands as input to another command (su, ssh, sh, etc)
(3 answers)
Closed 6 years ago.
Want to execute the following commands from any single script. How to do this?
Whenever I'm starting my putty session, on my unix machine, bash shell is coming, then I need to enter the following commands to setup my workspace.
Below is the exact procedure which I'm doing.
-bash-4.2$ bash
[userName#SystemName ~]$ su
getting admin rights
[root#SystemName userName]#
setting up environment variable for python project
[root#SystemName userName]# source xxxx.env
setting the path for my local workspace
[root#SystemName userName]# setxxxx /home/userName/SourceCode/
Now, I want all these commands to get executed from single script.
Thus, I had putted all these commands into a single shell script and tried to execute but only first instruction got executed. Why?
start.sh
#!/bin/bash
bash
su
source ssdt.env
setssdt /home/userName/projectName/
The first command in your script is bash, which opens a new shell that will run until you exit from it, before it will continue executing the other commands in your script. If you're just trying to make the script execute with bash, that's what the #! line at the top does. The su command will also open a subshell that will have to exit before the other commands will be run with normal privileges.