In my fish shell script 'hoge.fish`, I have a code to set envs.
#!/usr/local/bin/fish
set -x HOGE "hello"
but after I exec this script the env is not set correctly and outputs nothing.
./hoge.fish
echo $HOGE
I've tried these code but none of these worked.
set -gx HOGE "hello"
set -gU HOGE "hello"
how can I fix this?
OS: macOS High Sierra 10.13.6
fish version: 2.7.1
iTerm2: 3.2.0
When you ran the script, it probably set the environment variable correctly, but only in the process that was created when you ran the script....not in the parent session you ran the script from! When the script exited, the process and its environment were destroyed.
If you want to change the environment variable in your current environment, depending on what interactive shell you're using, you can use a command like source hoge.fish, which will execute the commands in your current session rather than a subprocess, so the environment variable changes will persist.
While sourceing, as in the original answer is definitely the correct mechanism, a comment from the OP to that answer mentioned that they would still prefer a solution that could be executed as a script.
As long as the variables are exported (set -x) in the script, it's possible (but still not necessarily recommended) to do this by execing into another fish shell inside the script:
#!/usr/bin/env fish
set -gx HOGE hello
exec fish
Executing ./hoge.fish will then have a fish shell with HOGE set as expected.
However, be aware:
This will result in two fish shell processes running, one inside the other. The first (parent) is the original fish shell. It will spawn a second (child) process based on the shebang line, which will then be replaced by the third instance from the exec line.
You can reduce the number of shells that are running simultaneously by starting the script with exec ./hoge.fish. That results in the shebang script replacing the parent process, and then being replaced by the exec line at the end of the script. However, you will still have run fish's startup twice to achieve what a simple source would have done with zero additional startups.
It's also important to realize the environment of the new shell will not necessarily be the same as that of the original shell. In particular, local variables from the original shell will not be present in the exec'd shell.
There are use-cases where these pitfalls are worth execing a new shell, but most of the time a simple source will be preferred.
Consider that if you run that from bash shell it will not export the variables with the -U option because it indicates to export to "fish universe" not outside.
If you stay inside fish's shell you still can do it like this:
#!/usr/local/bin/fish
set -Ux HOGE "hello"
And this is the result:
Welcome to fish, the friendly interactive shell
Type help for instructions on how to use fish
~/trash $ ./hoge.fish
~/tr ash $ echo $HOGE
hello
Remember to keep the first line so fish will interpret it properly.
Related
I am setting env variables using *.csh file to current terminal. When I use system("/bin/tcsh *.csh") in the perl script, the *csh file executing but not setting any env variables to current terminal.
When I use system("/bin/tcsh *.csh") in the perl script, the *csh file executing but not setting any env variables to current terminal.
sub veloce_env_setup_sub {
printf "\n\n\t -veloce_env_setup option enabled\n";
system("/bin/tcsh /proj/I2BZA1/users/ssudi/SCRIPTS/veloce_env/vlab_4p4p0/veloce_setup.csh");
}
Expected: env variables should set to current terminal after sourcing *.csh file.
Actual results: only prints are comming but not setting env variables to current terminal.
perldoc -q environment:
I {changed directory, modified my environment} in a perl script. How come the change disappeared when I exited the script? How do I get my changes to be visible?
Unix
In the strictest sense, it can't be done--the script executes as a different process from the shell it was started from. Changes to a process are not reflected in its parent--only in any children created after the change. There is shell magic that may allow you to fake it by eval()ing the script's output in your shell; check out the comp.unix.questions FAQ for details.
In your code the problem appears twice:
system spawns tcsh, which runs a script that sets environment variables. These environment variables only exist within the tcsh process. When system returns (i.e. when tcsh exits), the environment of the child process is gone.
Even if you managed to modify the environment of the perl script (which you can do by assigning to %ENV), that wouldn't affect the parent shell that perl was started from.
This can now be done with Env::Modify.
use Env::Modify qw(:tcsh source);
sub veloce_env_setup_sub {
printf "\n\n\t -veloce_env_setup option enabled\n";
source("/proj/I2BZA1/users/ssudi/SCRIPTS/veloce_env/vlab_4p4p0/veloce_setup.csh");
}
The environment of a child process doesn't affect the environment of the parent process. That is, a process that you start doesn't change the environment of the thing that started it.
If you want to set up the environment for a Perl script, you have some options. Which one works best for you depends on what you are trying to do.
Set up the options inside Perl. Instead of using a shell program, do it all in Perl by setting values in the %ENV hash. This works well if you just need it for that program. It's likely that whatever you are doing in tcsh you can do it Perl.
Instead of calling the shell script from Perl, call your Perl program from the shell script. Now the shell script is the parent process and the child process (the Perl program) inherits the parent's environment.
#!tcsh
setenv SOME_VALUE foo
perl my_program
In a child process, you could print the environment and read that from the parent process. You'd parse it and convert it appropriately. This is what the Env::Modify module does, but I wouldn't want that as my first option.
You can't access environment variables in a process that have been set by a child process. It's a fundamental property of how processes work.
You can set %ENV{'your_choice'} = 'as you like'; inside Perl.
Sure, it looks like a little bit hartverdrahtet (yt), but it works great again. So the environmental is mental just inner the mind of top instanced script and closed and removed on closing it.
Another way is calling system("set VARIABLE=VALUE");
Here the variable lefts after closing until next reboot.
I changed the environmental variable LD_LIBRARY_PATH from the Ubuntu terminal (because I was receiving an error) and the changes were applied when I ran code (a Python code) from the terminal. But when I ran the same script from the Visual Studio Code, the error remains. How to update the environmental variable so that Visual Studio Code sees it, as well?
Environment variables are passed from parent process to child process; they are not (say) global to the system or the user. If you change a variable in one shell, the change is only seen in that shell and any processes started from that shell. So the simplest solution is to change the variable and then start VSCode from that same shell:
$ export LD_LIBRARY_PATH=/some/useful/path
$ code
If you want to keep using that shell for other things, run it in the background:
$ code >/dev/null 2>&1 &
The redirection to /dev/null is needed because otherwise VSCode prints logging information periodically, and that output will be mixed with whatever else you're doing.
If you want to set the variable permanently, see the question How do I set a user environment variable? (permanently, not session). After following those instructions, you'll need to start a new shell (and possibly even logout and login) first so the settings take effect. Then launch VSCode from the new shell.
I have a Korn shell script at a location like /opt/apps/abc/folder/properties.env. I can execute it from Unix bash using the dot command:
. /opt/apps/abc/folder/properties.env
This works.
I have a Perl script abc.pl from which I am calling the script properties.env. I tried the following different:
system('/usr/bin/ksh','-c', '. /opt/apps/abc/folder/properties.env');
/usr/bin/ksh -c /opt/apps/abc/folder/properties.env;
system('. /opt/apps/abc/folder/properties.env');
None of the above work. I don't want to use exec because I want to return to the Perl script. What am I doing wrong?
The environment changes will only last as long as the life of the ksh session spawned by the system command. If you want the environment changes to affect the Perl script, then you have to source that file before you launch the Perl program.
If you need those environment variables in your perl code, (not in the environment where you called perl), you can also read and parse that properties.env and set the environment in the %ENV variable.
e.g
$ENV{'ENV_VAR1'}=VALUE_OF_ENV_VAR1
using system() spawn another process, as the other poster said. changing environment in the child does not affect the parent.
I am using a system call to do some tasks
system('myframework mycode');
but it complains of missing environment variables.
Those environment variables are set at my bash shell (from where I run the Perl code).
What am I doing wrong?
Does the system call create a brand new shell (without environment variable settings)? How can I avoid that?
It's complicated. Perl does not necessarily invoke a shell. Perldoc says:
If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing (this is /bin/sh -c on Unix platforms, but varies on other platforms). If there are no shell metacharacters in the argument, it is split into words and passed directly to execvp , which is more efficient.
So it actually looks like you would have the arguments passed right to execvp. Furthermore, whether the shell loaded your .bashrc, .profile, or .bash_profile depends on whether the shell is interactive. Likely it isn't, but you can check like this.
If you don't want to invoke a shell, call system with a list:
system 'mycommand', 'arg1', '...';
system qw{mycommand arg1 ...};
If you want a specific shell, call it explicitly:
system "/path/to/mysh -c 'mycommand arg1 ...'";
I think it's not the question of shell choice, since environment variables are always inherited by subprocesses unless cleaned up explicitly.
Are you sure you have exported your variables?
This will work:
$ A=5 perl -e 'system(q{echo $A});'
5
$
This will work too:
$ export A=5
$ perl -e 'system(q{echo $A});'
5
$
This wouldn't:
$ A=5
$ perl -e 'system(q{echo $A});'
$
system() calls /bin/sh as a shell. If you are on a somewhat different box like ARM it would be good to read the man page for the exec family of calls -- default behavior. You can invoke your .profile if you need to, since system() takes a command
system(" . myhome/me/.profile && /path/to/mycommand")
I've struggled for 2 days working on this. In my case, environment variables were correctly set under linux but not cygwin.
From mkb's answer I thought to check out man perlrun and it mentions a variable called PERL5SHELL (specific to the Win32 port). The following then solved the problem:
$ENV{PERL5SHELL} = "sh";
As is often the case - all I can really say is "it works for me", although the documentation does imply that this might be a sensible solution:
May be set to an alternative shell that perl must use internally for executing "backtick" commands or system().
If the shell used by perl does not implicitly inherit the environment variables then they will not be set for you.
I messed with environment variables being set for my script on this post where I needed the env variable $DBUS_SESSION_BUS_ADDRESS to be set, but it wouldn't when I called the script as root. You can read through that, but in the end you can check whether %ENV contains your needed variables and if not add them.
From perlvar
%ENV
$ENV{expr}
The hash %ENV contains your current environment. Setting a value in "ENV" changes
the environment for any child processes you subsequently fork() off.
My problem was that I was running the script under sudo and that didn't preserve all my user's env variables, are you running the script under sudo or as some other user, say www-data (apache)?
Simple test:
user#host:~$ perl -e 'print $ENV{q/MY_ENV_VARIABLE/} . "\n"'
and if that doesn't work then you will need to add it to %ENV at the top of your script.
try system("echo \$SHELL"); on your system.
I found an odd problem when I run a simple csh script on Solaris.
#!/bin/csh
echo $LD_LIBRARY_PATH
Let's call this script test. When I run this:
shell> echo $LD_LIBRARY_PATH
shell> /usr/lib:/usr/openwin/lib:/usr/dt/lib:/usr/local/lib:/lib:/my_app/lib
shell> ./test
shell> /usr/lib:/usr/openwin/lib:/usr/dt/lib:/usr/local/lib:/lib
They print out totally different values for $LD_LIBRARY_PATH. I can't figure out why. (It's OK on my linux machine)
Thanks!
Do you set $LD_LIBRARY_PATH in your $HOME/.cshrc?
You really shouldn't if you do, since it often just breaks software, but changing the first line of the script to #!/bin/csh -f will cause your script to not read .cshrc files at the start, protecting you from other users who made that mistake.
If your interactive shell is in the sh/ksh family you might have set LD_LIBRARY_PATH using "set" but not exported it. In that case it's new value will be set like a normal variable, but not exported into the environment. But it's more likely that your script is reinitializing the variable.
You can use the "env" command to dump out the exported environment from the interactive shell to check this.