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.
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 am trying to run a perl script from within a *.csh script, but I get the following error:
Can't open perl script "checkLength.perl": No such file or directory
I think it has something to do with the path of the perl script. I can run a perl script fine when it's not being called within the shell script, but a perl script won't run when I have it being called in the cshell script.
The shebang I use for the perl script is : #!/usr/bin/perl. I checked, and perl is located there (not in /usr/bin/env perl). I made sure it's executable.
Do I need to edit the $PATH to get this to work? I'm confused because if I run a perl script without calling it within another csh script, it runs just fine.
Of course one obvious solution to your problem would be to simply use the full path to the script. But this is often not preferable, as the script would brake on installations that do not mirror exactly the original structure.
So there are two possibilities:
Either you put your perl script into a well defined location that is contained in your PATH variable so any program that runs under the respective users environment finds it.
Or you have some well defined location relative to the location of your calling script. Say your bash script is located in somedir and you perl script is in somedir/subdir, then your call would be subdir/perlscript.pl. Then, to become independent of possible changes in the working directory of the caller, you could determine the current full path of the perl script to be called on start of the bash script.
A template for this would be:
#!/bin/bash
FULLPATH=$(pwd)/subdir/somescript.pl
# do something else, cd ...
$FULLPATH
I am assuming your Perl script is kept in a fixed path relative to your bash script. Assuming your directory structure to be like so:
(BASEDIR)/bin/example.sh
(BASEDIR)/perl/example.pl
To allow you to run your bash script from anywhere in your system you must specify the relative path to your Perl script by getting the BASEDIR.
#!/bin/bash
BASEDIR=$(dirname $0)
perl $BASEDIR/../perl/example.pl
What we are doing above is finding the location of your bash script(BASEDIR/bin) that you call and then finding the relative location of the Perl script using the location of the bash script as reference. Now you will be able to call the bash script from anywhere and run your Perl script normally.
I have a series of perl scripts that I want to run one after another on a unix system. What type of file would this be / could I reference it as in documentation? BASH, BATCH, Shell Script File?
Any help would be appreciated.
Simply put the commands you would use to run them manually in a file (say, perlScripts.sh):
#!/bin/sh
perl script1.pl
perl script2.pl
perl script3.pl
Then from the command line:
$ sh perlScripts.sh
Consider using Perl itself to run all of the scripts. If the scripts don't take command line arguments, you can simply use:
do 'script1.pl';
do 'script2.pl';
etc.
do 'file_name' basically copies the file's code into the current script and executes it. It gives each file its own scope, however, so variables won't clash.
This approach is more efficient, because it starts only one instance of the Perl interpreter. It will also avoid repeated loading of modules.
If you do need to pass arguments or capture the output, you can still do it in a Perl file with backquotes or system:
my $output = `script3.pl file1.txt`; #If the output is needed.
system("script3.pl","file1.txt"); #If the output is not needed.
This is similar to using a shell script. However, it is cross-platform compatible. It means your scripts only rely on Perl being present, and no other external programs. And it allows you to easily add functionality to the calling script.
I am looking for a nice way to get the following done:
So I have a script that I need to run in Python in Unix by calling from a Perl script that was, in turn, called from my Excel VBA macro in Windows using Plink. The Python script, due to dependency issues, has to run in either csh or bash, and I will need to use export/setenv to add a few libraries before running the script. However by default, perl runs in sh shell and as such, there is no way I can add in all the dependencies and have the Python script to run.
So, I am just wondering if there is EITHER: 1. a way for me to add dependencies to sh shell in the perl script, OR 2. force my perl script to run in csh (preferred, since for some reason .bashrc for the account runs into permission issues).
Thanks a lot!
How about "3. Set the appropriate environment variable in the Perl or Python scripts"?
$ENV{'PATH'} = ...
...
os.environ['PATH'] = os.pathsep.join(newpaths + os.environ['PATH'].split(os.pathsep))
(dunno how to get the path separator in Perl, sorz)
To force the shell to csh, try the following in Perl :
`/bin/csh -c "command_name"`;
Edit:
You can use ENV variable, like this. Try that :
$s = `/bin/bash -c 'VAR_FOO=753; echo \$VAR_FOO'`;
print $s;
I ended up just change the .cshrc script, apparently the addition to PATH, for some reason, did not work for me. After that, everything runs smoothly by putting all into one line
so basically it looks something like this
/path/to/.cshrc && /python/path/to/python
Hope that helps!
I want to source a shell script from within Perl and have the environment variables be available in Perl, but I'm not sure if there's an elegant way to do it. Obviously, using system() won't work since it runs in a forked process, and all environment changes will be lost. I think there's a CPAN module that can do it, but I prefer not to use external modules.
I've seen two solutions that would not work in my case:
Have a wrapper that calls the shell script, and then calls the Perl script. I do not know ahead of time which of my shell scripts I need to call.
Manually opening the shell script and scraping for arg=value pairs. This won't work either because the shell script is not a simple list of ARG=VALUE, but rather contain a bunch of conditionals, and variables can have different values depending on certain conditions.
sh -c "source script; env" should output the environment at the end of script as name=value pairs, which you then can parse from your perl script (as Perl is a language made for parsing, this should be easy).
You can do this by installing external module from CPAN which is Shell::Source
$env_path= Shell::Source->new(shell=>"tcsh",file=>"../path/to/file/temp.csh");
$env_path->inherit;
As perl creates its own instance while running on a shell, so we can not set environment path for the main shell as the perl's instance will be like sub shell of the main shell. Child can not set environment paths for parents.
Now till the perl's sub shell will run you'll be able to access all the paths present in temp.csh by using Shell::Source