On Ubuntu Server 16.10 x64 with fish 2.3.1, my uru_rt exe generates this function on stdout
function uru
set -x URU_INVOKER fish
# uru_rt must already be on PATH
uru_rt $argv
if test -d "$URU_HOME" -a -f "$URU_HOME/uru_lackee.fish"
source "$URU_HOME/uru_lackee.fish"
else if test -f "$HOME/.uru/uru_lackee.fish"
source "$HOME/.uru/uru_lackee.fish"
end
end
when run via uru_rt admin install. The uru function provides the golang-based cross-platform ruby version manager tool https://bitbucket.org/jonforums/uru
On bash systems, I inject the uru function by placing eval "$(uru_rt admin install)" in a startup file so that uru is present in the shell.
On fish, running eval (uru_rt admin install) rewards me with this failure
$ eval (uru_rt admin install)
Missing end to balance this begin
- (line 1): begin; function uru set -x URU_INVOKER fish # uru_rt must already be on PATH uru_rt $argv if test -d "$URU_HOME" -a -f "$URU_HOME/uru_lackee.fish" source "$URU_HOME/uru_lackee.fish" else if test -f "$HOME/.uru/uru_lackee.fish" source "$HOME/.uru/uru_lackee.fish" end end
^
from sourcing file -
called on line 60 of file /usr/share/fish/functions/eval.fish
in function “eval”
called on standard input
source: Error while reading file “-”
I've also tried set u1 (uru_rt admin install); eval "$u1" with the same result.
As expected, when I do uru_rt admin install > ~/.config/fish/functions/uru.fish the uru function becomes persistently available. While this is an option, my preference is to use eval in ~/.config/fish/config.fish
As a noob to fish, how do I dynamically inject this uru function into the environment using eval similar to bash's eval "$(uru_rt admin install)"?
Fish's eval is a wrapper function around its source builtin, and it seems there's some weirdness (maybe even a bug) going on with it's argument splitting when you pass multiple lines..
However, in this case it's simpler, faster and actually working if you just use source, like uru_rt admin install | source.
That assumes though that uru_rt admin install really needs to be called - if all it does is print that code to stdout, without changing it, you can also simply save the function, e.g. in ~/.config/fish/functions/uru.fish.
Related
I am writing a perl script, and I want to run a simple shell command to use a certain version of NVM:
Here is my code snippet:
print "\n*** Switching to correct nvm environment for dashboard builds\n";
system("nvm use 8.12.0") == 0 or die $?;
But I am getting the following error:
Can't exec "nvm": No such file or directory
Can someone help?
Update (June 30, 2021):
I also tried adding the command:
my $nvm_version = "8.12.0";
system ("bash", "-lic", "nvm use $nvm_version");
But nothing happens:
I'm not familiar with nwm, but I think I get the gist of what it does. And if so, the attempt is fundamentally flawed. Even if you fixed this to run the proper shell so that nvm could run, I believe all the tool does is change the shell's environment variables, a shell you immediately exit. This means it would have no effect even if if it ran successfully.
Again, it this tool does what I think it does, such tool are meant to be used in interactive shells. In other instances, you simply use the path the to correct executable instead of relying on the PATH.
With that in mind, you can use the following to run the command in bash:
# Non-interactive shell.
system("bash", "-c", "nvm use 8.12.0")
or
# Interactive shell.
# This is improper and fragile as interactive shells
# often create aliases that override basic commands.
system("bash", "-ic", "nvm use 8.12.0")
Just to reiterate, at least one of these will allow the command to run (if it normally works from bash), but I believe it's unlikely this will produce the results you expect.
The nvm command is shell function which is different from a shell command. Also the nvm command is not an exported function so it will not be seen by sub shells. For example, in Bash shell:
$ nvm ls
-> v15.0.1
$ my-test-script.sh
./my-test-script.sh: line 3: nvm: command not found
where my-test-script.sh is:
#! /bin/bash
nvm use 16.4
The error nvm: command not found is because nvm is not exported. I can source the script in the current shell context to make it work:
$ source my-test-script.sh
Now using node v16.4.0 (npm v7.18.1)
$ node --version
v16.4.0
So a Perl script cannot change the node version of the current shell, but it can calculate the version and pass it back to shell, which can set the version. For example:
$ nvm use $(perl -E'$v=15.0; print $v')
Now using node v15.0.1 (npm v7.0.3)
I have a perl script which works fine from shell but doesn't work from web (lighttpd + mod_cgi). I found out that problem is with the following string
my $lastupdate = `/opt/mongo/bin/mongo 127.0.0.1:27117/getVersion -u test -p test --eval 'db.polling.find({},{"_id":0,"host":0,"ports":0}).sort({"date":-1}).limit(1).forEach(function(x){printjson(x)})' | awk -F'"' '/date/{print \$4}' |sed 's/T/,/;s/Z//'`;
As i understood, when running from cgi, string is not being splitted. So i have done this by my own
my $lastupdate = system('/opt/mongo/bin/mongo', '127.0.0.1:27117/getVersion', '-u', 'test', '-p', 'test', '--eval', 'db.polling.find({},{"_id":0,"host":0,"ports":0}).sort({"date":-1}).limit(1).forEach(function(x){printjson(x)})', '|', 'awk', '-F', '"', '/date/{print', '\$4}', '|sed', 's/T/,/;s/Z//');
Script works now but gives me unexpected value (differs from shell's run value).
What did i miss?
P.S. I know that there are smarter ways to interact mongoDB from perl, but my env is totally firewalled. I have access neither to CPAN, nor to rh repos and perl mongoDB driver has too much deps to install it manually.
The environment that you run a program under from a shell is completely different to the environment that the same program gets when run from a web server. Most obviously, it will be run as a different user - one who will have far more restricted filesystem permissions that the average user.
You can (partly) simulate this by working out which user your web server runs as (perhaps apache, www or nobody) and using sudo to run your program as that user. This might well reveal what the problem is.
You can't just switch from backticks to system(). Backticks return the output from running the command line and system() returns a value which requires some interpretation. That'll be why you're seeing a different result.
I'm running a script in solaris 11 with different results depending of the shell used.
The script has an echo redirecting to a file given by an environment value:
echo "STARTING EXEC" >> $FILE
ps. EXEC is just the message the script show, it's not using exec command.
If I execute the script without the variable FILE defined (using /usr/bin/ksh):
./start.sh[10]: : cannot open
and the script continue the execution.
The flags for ksh are:
echo $-
imsuBGEl
But if I change to /usr/xpg4/bin/sh, the script show me the echo in stdout and there is no error shown.
The flags for xpg4 sh are:
echo $-
imsu
I tried to change the flags with set +- (I can't remove El flags, but BG are removed ok), but can't get the same behavior.
Is there anything I can do to get the same result using ksh without cannot open error?
/usr/bin/ksh --version
version sh (AT&T Research) 93u 2011-02-08
I'll want the script keep going, showing the message in stdout, instead of showing the error just like it does now.
Like shellter said in the comments, the good thing to do is to check if the FILE variable is defined before doing anything. This is a script migration from an HPUX to a SOLARIS environment, and client think they must have the same result as before (we unset FILE variable before execution to test it).
You are likely running Solaris 11, not Solaris 64.
Should you want to have your scripts to work under Solaris 11 without having to search everywhere the bogus redirections, you can simply replace all shebangs (first line) by #!/usr/xpg4/bin/sh.
The final solution we are going to take is to install the ksh88 package and use it like default shell (/usr/sunos/bin/ksh). This shell have the same behavior the client had before, and we can let the scripts with no modifications.
The ksh used in solaris 11 is the 93 (http://docs.oracle.com/cd/E23824_01/html/E24456/userenv-1.html#shell-1)
Thanks #jlliagre and #shellter for your help.
I made a perl script to change owner of a file owned by some other user. Script is complete. My administrator save that in /sbin directory and set uid for it using chmod u+s name_of_script. But when I run this script it gives me error that chown operation is not permitted. I made a C program and it works by following same steps. So my question is if setuid is working for perl then I should not get that error because C code did not give me any error. So can i setuid for perl script or I should go with c code.
Don't tell me to ask administrator to change owner each time. Actually in server I have user name staging and I am hosting a joomla site in it. Now when I install some plugin then files related to that plugin are owned by www-data. So that's why I do not want to go to admin each time. Or you can give me some other solution also regarding my problem.
Many unix systems (probably most modern ones) ignore the suid bit on interpreter scripts, as it opens up too many security holes.
However, if you are using perl < 5.12.0, you can run perl scripts with setuid set, and they will run as root. How it works is that when the normal perl interpreter runs, and detects that the file you are trying to execute has the setuid bit set, and it then executes a program called suidperl. Suidperl takes care of elevating the user's privileges, and starting up the perl interpreter in a super-secure mode. suidperl is itself running with setuid root.
One of the consequences of this is that taint mode is turned on automatically. Other additional checks are also performed. You will probably see messages like:
Insecure $ENV{PATH} while running setuid at ./foobar.pl line 3.
perlsec provides some good information about securing such scripts.
suidperl is often not installed by default. You may have to install it via a separate package. If it is not installed then you get this message:
Can't do setuid (cannot exec sperl)
Having said all of that - you would be much better off using sudo to execute actions with elevated privileges. It is much more secure as you can specify exactly what is allowed to be executed via the sudoers file.
As of perl 5.12.0, suidperl was dropped. As a result, if you want to run a perl script on perl >= 5.12.0 with setuid set, you would have to write your own C wrapper. Again I recommend sudo as a better alternative.
No, you cannot use setuid aka chmod +s on scripts. The script's interpreter would be the thing that would actually need to be setuid, but doing that is a really bad idea. REALLY bad.
If you absolutely must have something written in Perl as setuid, the typical thing to do would be to make a small C wrapper that is setuid and executes the Perl script after starting. This gives you the best of both worlds in having a small and limited setuid script but still have a scripting language available to do the work.
If you have a sudo configuration that allows it (as most desktop linux distributions do for normal users), you can start your perl script with this line:
#!/usr/bin/env -S -i MYVAR=foo sudo --preserve-env perl -w -T
Then in your script before you use system() or backticks explicitly set your $ENV{PATH} (to de-taint it):
$ENV{PATH} = '/usr/bin';
Other environment variable that your script explicitly mentions or that get implicitly used by perl itself will have to be similarly de-tainted (see man perlsec).
This will probably (again depending on your exact sudo configuration) get you to the point where you only have to type in your root password once (per terminal) to run the script.
To avoid having to type your password at all you can add a line like this to the bottom of /etc/sudoers:
myusername ALL=(ALL) NOPASSWD:ALL
Of course you'd want to be careful with this on a multi-user system.
The -S options to env splits the string into separate arguments (making it possible to use options and combinations of programs like sudo/perl with the shebang mechanism). You can use -vS instead to see what it's doing.
The -i option to env clears the environment entirely.
MYVAR=foo introduces an environment variable definition.
The --preserve-env option to sudo will preserve MYVAR and others.
sudo sets up a minimal environment for you when it finds e.g. PATH to be missing.
The -i option to env and --preserve-env option to sudo may both be omitted and you'll probably end up with a slightly more extensive list of variables from your original environment including some X-related ones (presumably the ones the sudo configuration considers safe). --preserve-env without -i will end up passing along your entire unsanitized environment.
The -w and -T options to perl are generally advisable for scripts running as root.
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.