I have this command that I load (example.sh) works well in the unix command line.
However, if I execute it in Perl using the system or ` syntax, it doesn't work.
I am guessing certain settings like environment variables and other external sh files weren't loaded.
Is there an example coding to ensure it will work?
More Updates on coding execution failure (I have been trying with different codes):
push (#JOBSTORUN, "cd $a/$b/$c/$d; loadproject cats; sleep 60;");
...
my $pm = new Parallel::ForkManager(3);
foreach my $job (#JOBSTORUN) {
$pm->start and next;
print(`$job`);
$pm->finish;
}
print "\n\n[DONE] FINISHED EXECUTING JOBS\n";
Output Messages:
sh: loadproject: command not found
Can you show us what you have tried so far? How are you running this program?
My first suspicion wouldn't be the environment if you are running it from a login shell. any Perl script you start (well, any program, really) inherits the same environment. However, if you are running the program through cron, then that's a different story.
The other mistakes I usually make in these situations is specifying the relative paths incorrectly. The paths are fine from the command line, but my Perl script has some other current working directory.
For general advice, see Interact with the system when Perl isn't enough. There's also a chapter in Learning Perl about this.
That's about the best advice you can hope for given the very limited information you've shared with us.
Related
How can I call a script with that preceding argument before the script path using Task Scheduler or a batch file? plackup E:\Mojolicious_server.pl
So I have multiple Mojolicious applications.
I have bundled them all into a psgi server using plack.
My plack script looks like this...
use Plack::Builder;
use lib 'push_the_button/lib';
use lib 'Phone_Book/lib';
use Mojo::Server::PSGI;
use Plack::Session::Store;
use Data::Dumper;
use File::Basename;
my $current_directory = dirname(__FILE__);
my $push_the_button, $phone_book;
{
my $server_1 = Mojo::Server::PSGI->new;
$server_1->load_app($current_directory.'/Phone_Book/script/application');
$phone_book = sub { $server_1->run(#_) }
}
{
my $server_2 = Mojo::Server::PSGI->new;
$server_2->load_app($current_directory.'/push_the_button/script/push_the_button.pl');
$push_the_button = sub { $server_2->run(#_) }
}
builder {
mount "/phone_book" => builder {$phone_book};
mount "/push_the_button" => builder {$push_the_button};
};
Now I want to run this as a scheduled task at system startup.
to run this script normally, I would go to cmd
pushd c:\strawberry\perl\bin
Then I would run this command
plackup E:/Mojolicious_Server.pl
My issue seems to be that plackup portion.
I have tried adding plackup E:/Mojolicious_Server.pl to the Arguments portion. I have also tried adding plackup to the arguments portion and E:/Mojolicious_Server.pl in the start in portion. Of course C:\strawberry\perl\bin\perl.exe is the Program to start.
Once I tried all the variations I could think of (including variations on double and single quotes), I wrote a very simple batch file to run (even just in the terminal for testing). It looks like this.
#echo off
call "C:\Strawberry\perl\bin\perl.exe" "plackup E:\Mojolicious_Server.pl"
Which says "Can't open perl script".
I went ahead and tried another route using another perl script to execute my command...
#! C:\strawberry\perl\bin\perl.exe
`plackup E:\\Mojolicious_Server.pl`;
This at least completes successfully in the Task Scheduler, doesn't actually do anything though...
Just as a last resort (obviously wouldn't work), I added plackup E:\\Mojolicious_Server.pl; at the end of my Mojolicious_Server.pl script and run that script. Didn't work as I expected (calling a script thats already running).
This seems like it should be very easy, I'm sorry if I'm missing something simple. Any notion in the right direction would be appreciated.
Also I am only doing it this way because I am strictly on a windows environment. If there is a better way, again, please just a nudge in the right direction.
As stated in the comments of the question, all it takes is to invoke the sequence plackup E:/Mojolicious_Server.pl making sure that you add the full path to the plackup script. In the case of #gregnnylf94, it was:
c:\strawberry\perl\site\bin\plackup E:\Mojolicious_server.pl
This is so because cron jobs do not have the same context as shell ones. The most frequent problem comes from the PATH variable that is key to finding what you want to execute.
This is true in Windows and Linux systems alike.
I'm sure this is an easy fix, but I need to use "script" (and not collect standard in/out/error) for my project. I'm somewhat new to Perl, so please bear with me.
I have a Perl script that works fine. When I run it I generally type script > filename before I run Perl.
$script > file.log
bash-3.2$ perl foobar.pl
This runs fine, and when I'm done I type exit or control D to stop the script and save the file. All I'd like to do is incorporate the script command in Perl and then automatically capture the file when the program stops running (12-16 hours). The problem I have is that is I call in system("script > file.log"); and them call system("perl foobar.pl"); it hangs at the bash-3.2$ prompt. The only way to get Perl to work is control D or exit, stopping the script function.
Anyone have any idea how to fix this? While it's easy to start with script before invoking Perl, if I'm a mole and forget, I have to rerun the program (which takes a long time).
Have you considered using system("script -c 'perl foobar.pl' file.log")?
Note that I'm aware that this is probably not the best or most optimal way to do this but I've run into this somewhere before and I'm curious as to the answer.
I have a perl script that is called from an init that runs and occasionally dies. To quickly debug this, I put together a quick wrapper perl script that basically consists of
#$path set from library call.
while(1){
system("$path/command.pl " . join(" ",#ARGV) . " >>/var/log/outlog 2>&1");
sleep 30; #Added this one later. See below...
}
Fire this up from the command line and it runs fine and as expected. command.pl is called and the script basically halts there until the child process dies then goes around again.
However, when called from a start script (actually via start-stop-daemon), the system command returns immediately, leaving command.pl running. Then it goes around for another go. And again and again. (This was not fun without the sleep command.). ps reveals the parent of (the many) command.pl to be 1 rather than the id of the wrapper script (which it is when I run from the command line).
Anyone know what's occurring?
Maybe the command.pl is not being run successfully. Maybe the file doesn't have execute permission (do you need to say perl command.pl?). Maybe you are running the command from a different directory than you thought, and the command.pl file isn't found.
There are at least three things you can check:
standard error output of your command. For now you are swallowing it by saying 2>&1. Remove that part and observe what errors the system command produces.
the return value of system. The command may run and system may still return an exit code, but if system returns 0, you know the command was successful.
Perl's error variable $!. If there was a problem, Perl will set $!, which may or may not be helpful.
To summarize, try:
my $ec = system("command.pl >> /var/log/outlog");
if ($ec != 0) {
warn "exit code was $ec, \$! is $!";
}
Update: if multiple instance of the command keep showing up in your ps output, then it sounds like the program is forking and running itself in the background. If that is indeed what the command is supposed to do, then what you do NOT want to do is run this command in an endless loop.
Perhaps when run from a deamon the "system" command is using a different shell than the one used when you are running as yourself. Maybe the shell used by the daemon does not recognize the >& construct.
Instead of system("..."), try exec("...") function if that works for you.
How would I determine what script, program, or shell executed my Perl script?
Example: I might want to have human readable output if executed from shell (customized for each type of shell), a different type of output if called as a script from another perl script, and a machine readable format if executed from a program such as a continuous integration server.
Motivation: I have a tool that changes its output based on which shell executes it. I'd normally implement this behavior as an option to the script, but this tool's design doesn't allow for options. Other shells have environment variables that indicate what shell is running. I'm working on a patch to support Powershell, which has no such special variable.
Edit: Many of these answers happen to be linux specific. Unfortuantely, Powershell is for Windows. getppid, the $ENV{SHELL} variable, and shelling out to ps won't help in this case. This script needs to run cross-platform.
You use getppid(). Take this snippet in child.pl:
my $ppid = getppid();
system("ps --no-headers $ppid");
If you run it from the command line, system will show bash or similar (among other things). Execute it with system("perl child.pl"); in another script, e.g. parent.pl, and you will see that perl parent.pl executed it.
To capture just the name of the process with arguments (thanks to ikegami for the correct ps syntax):
my $ppid = getppid();
my $ps = `ps --no-headers -o cmd $ppid`;
chomp $ps;
EDIT: An alternative to this approach, might be to create soft links to your script, make the different contexts use different links to access your script and inspect $0 to build logic around that.
I would suggest a different approach to accomplish your goal. Instead of guessing at the context, make it more explicit. Each use case is wholly separate, so have three different interfaces.
A function which can be called inside a Perl program. This would likely return a Perl data structure. This is far easier, faster and more reliable than parsing script output. It would also serve as the basis for the scripts.
A script which outputs for the current shell. It can look at $ENV{SHELL} to discover what shell is running. For bonus points, provide a switch to explicitly override.
A script which can be called inside a non-Perl program, such as your continuous integration server, and issue machine readable output. XML and/or JSON or whatever.
2 and 3 would be just thin wrappers to format the data coming out of 1.
Each is tailored to fit its specific need. Each will work without heuristics. Each will be far simpler than trying to guess the context and what the user wants.
If you can't separate 2 and 3, have the continuous integration server set an environment variable and look for it.
Depending on your environment, you may be able to pick it up from the environment variables. Consider the following code:
/usr/bin/perl -MData::Dumper -e 'print Dumper(\%ENV);' | grep sh
On my Ubuntu system, it gets me:
'SHELL' => '/bin/bash',
So I guess that says I'm running perl from a bash shell. If you use something else, the SHELL variable may give you a hint.
But let's say you know you're in bash, but perl is run from a subshell. Then try:
/bin/sh -c "/usr/bin/perl -MData::Dumper -e 'print Dumper(\%ENV);'" | grep sh
You will find:
'_' => '/bin/sh',
'SHELL' => '/bin/bash',
So the shell is still bash, but bash has a variable $_ which also show the absolute filename of the shell or script being executed, which may also give a valuable hint. Similarily, for other environments there will most probably be clues left in the perl %ENV hash that should give you valuable hints.
If you're running PowerShell 2.0 or above (most likely), you can infer the shell as a parent process by examining the environment variable %psmodulepath%. By default, it points to the system modules under %windir%\system32\windowspowershell\v1.0\modules; this is what you would see if you examine the variable from cmd.exe.
However, when PowerShell starts up, it prepends the user's default module search path to this environment variable which looks like: %userprofile%\documents\windowspowershell\modules. This is inherited by child processes. So, your logic would be to test if %psmodulepath% starts with %userprofile% to detect powershell 2.0 or higher. This won't work in PowerShell 1.0 because it does not support modules.
This is on Windows XP with PowerShell v2.0, so take it with a grain of salt.
In a cmd.exe shell, I get:
PSModulePath=C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules\
whereas in the PowerShell console window, I get:
PSModulePath=E:\Home\user\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsP
owerShell\v1.0\Modules\
where E:\Home\user is where my "My Documents" folder is. So, one heuristic may be to check if PSModulePath contains a user dependent path.
In addition, in a console window, I get:
!::=::\
in the environment. From the PowerShell ISE, I get:
!::=::\
!C:=C:\Documents and Settings\user
I have a perl script (part of the XMLTV family of "grabbers", specifically tv_grab_oztivo).
I can successfully run it like this:
/sw/bin/perl /path/to/tv_grab_oztivo --output /path/to/tv.xml
I use the full paths to everything to eliminate issues with the Working Directory. Permissions shouldn't be a problem.
So, if I run it from the Terminal (Mac OSX) it works just fine.
But when I set it to run via a cron job, nothing appears to happen at all. No output is created etc.
There isn't anything wrong with the crontab as far as I can see, because if I substitute a helloworld.pl for the actual script, it runs just fine at the right time.
So, what can I do to debug? I can see from looking at %ENV in the two cases that the environment is very different, but what other approaches can I take to debugging? How can I see the output of the cron job, which might be some kind of perl "die" message or "not found" message from the shell or whatever?
Or should I be trying to somehow give the cron version of the command the same environment as when it's running as me?
It's often because you don't get the full environment when running under cron. Best bet is to capture the ouput by using the command:
( /sw/bin/perl /path/to/tv_grab_oztivo ... ) >/tmp/qq 2>&1
and then have a look at /tmp/qq.
If it does turn out to be a missing environment, then you may need to put:
. ~/.profile
or something similar, into the execution chain of your cron job, such as:
( . ~/.profile ; /sw/bin/perl /path/to/tv_grab_oztivo ... ) >/tmp/qq 2>&1
If you're looking at %ENV in the two cases, I'd suggest that, as a first step in your perl script, set %ENV to what it is in a cron job, and then trying to run it from the command line. You may need to exec yourself once for this to take full control:
BEGIN {
if (exists $ENV{something_in_your_env_not_in_cron}) {
%ENV = (...);
exec $^X, $0, #ARGV;
}
}
Now try running it, and seeing if there's anything you can do to debug it (including running under perl -d if required). Most likely, you'll find that you end up adding items back into %ENV one at a time until it magically starts working (LD_LIBRARY_PATH is a good one for this, but ORACLE_HOME or DB2HOME for Oracle or DB2 apps might be good choices, too). Then you can either set the variable in your script, or in the crontab.
I'd run a simple shell script by absolute path from the cron command.
Inside that script, I'd ensure that I trapped stdout and stderr to a known (or knowable) file. I'd also ensure that enough of your environment is set. On Unix, you get almost no environment set at all when you run a command via cron - I'm not sure about MacOS X. The standard culprit for problems is PATH. I have a separate .cronfile that sets my working environment enough that I usually don't have problems - that's an analogue of .profile.
On occasion if you can't figure out what's going wrong with your command line, the simplest way to fix it is to turn the whole thing into a shell script. Ideally you shouldn't have to do this, but it can be the fastest way to solve the problem.
File: /files/cron1.sh
#!/bin/sh
/sw/bin/perl /path/to/tv_grab_oztivo --output /path/to/tv.xml
And then in cron:
/files/cron1.sh
This allows you to test the script independent of cron. Remember though that your login shell runs with different environment variables than cron does.
cron usually captures the output of stdout and stderr and e-mailes any output to the crontab owner.
Did you double check your crontab entry to make sure it's valid and will execute at the right time?
Make sure that the script does not need any environment variables set. Otherwise wrap it in another (bash) script, where you can set the environment variables that the other script expects.