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")?
Related
I'm coding a Perl script to generate images with text in them. I'm on a Linux machine. I'm using pbmtextps. When I try to run pbmtextps in Perl with a system call like this
system("pbmtextps -fontsize 24 SampleText > out.pbm");
I get this error message
pbmtextps: failed to run Ghostscript process: rc=-1
However, if I run the exact same pbmtextps command from the command-line outside of Perl, it runs with no errors.
Why does it cause the ghostscript error when I run it from inside a Perl script?
ADDITIONAL INFO: I tried to hack around this by creating a C code called mypbmtextps.c which does the exact same thing with a C system call. That works from the command line. No errors. But then when I call that C program from the Perl script, I get the same ghostscript error.
ANSWER: I solved it. The problem was this line in the PERL script:
$SIG{CHLD} = 'IGNORE';
When I got rid of that (which I need for other things, but not in this script) it worked okay. If anyone knows why that would cause a problem, please add that explanation.
Ah-ha. Well, the SIGCHLD is required for wait(), and so required for perl to be able to retrieve the exit status of the child process created by system(). In particular, system() always returns -1 when SIGCHLD is ignored. $? will also be unavailable with SIGCHLD blocked.
What printed the error message? pbmtextps, or your perl script?
As far as I know, the signal handler for your perl process shouldn't affect the signal handler for the child processes, but this could depend on your version of perl and your OS version. On my Linux Mint 13 with Perl 5.14.2 the inner perl script prints 0, with the outer script printing -1:
perl -e '$SIG{CHLD}= "IGNORE"; print system(q{perl -e "print system(q(/bin/sleep 1))"})'
Is your perl script modifying the environment?
You can test with
system("env > /tmp/env.perl");
and then compare it to the environment form your shell:
env > /tmp/env.shell
diff /tmp/env.shell /tmp/env.perl
Is the perl script also being run from the shell, or is it being run from some other process like cron or apache? (in particular, you should check $PATH)
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 $output = `script3.pl file1.txt`; #If the output is needed.
system("script3.pl","file1.txt"); #If the output is not needed.
This is similar to using a shell script. However, it is cross-platform compatible. It means your scripts only rely on Perl being present, and no other external programs. And it allows you to easily add functionality to the calling script.
Note that I'm aware that this is probably not the best or most optimal way to do this but I've run into this somewhere before and I'm curious as to the answer.
I have a perl script that is called from an init that runs and occasionally dies. To quickly debug this, I put together a quick wrapper perl script that basically consists of
#$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.
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 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.