Develop Reference

Run .sh with Java

I have a shell script which I'm trying to call from Java. The shell script contains:
cat /dev/tty.USB0 > file.txt
In my Java code I am using:
Process p= Runtime.getRuntime().exec("/home/myname/Scrivania/capture.sh");
But it does not work. When I run it from the terminal it works as expected.

You can't directly execute a .sh script like this, since it's not an executable. Instead, you have to run /bin/sh -c /home/myname/Scrivania/capture.sh instead.

First of all, it's not a good style to work with OS-based features in Java code. Instead of that i suggest you to work with system input/output streams only. For example if your program should handle output of your script, you can do something like:
cat /dev/tty.USB0 > java YourMainClass
and then work directly with System.in.
Even if your program is more complicated than script output consumer, you can rewrite it to remove all OS-based parts from your program, it'll make your code more stable and maintainable.

What you are doing works. Well, it should.
My guess as to what is/seems wrong is this: You might be looking for the output file "file.txt" in the wrong place.
Here's a little experiment
System.out.println("Output file - " + new File("file.txt"));
Process p= Runtime.getRuntime().exec("/home/myname/Scrivania/capture.sh");
The first line should tell you where to look for your file.
P.S. Of course, do remember to import java.io.File :)

php exec function not working for jar files [duplicate]

The exec command doesn't work on my server, it does not do anything, I've had safe_mode off, and verified that all the console commands are working, I've tried with absolute paths. I've checked the permissions on the applications and all the applications I need have execution permissions. I don't know what else to do, here are the rundown of the codes I've tried.
echo exec('/usr/bin/whoami');
echo exec('whoami');
exec('whoami 2>&1',$output,$return_val);
if($return_val !== 0) {
echo 'Error<br>';
print_r($output);
}
exec('/usr/bin/whoami 2>&1',$output,$return_val);
if($return_val !== 0) {
echo 'Error<br>';
print_r($output);
}
The last two codes display:
Error
Array ( )
I've contacted the server service and they can't help me, they don't know why the exec command isn't working.

have a look at /etc/php.ini , there under:
; This directive allows you to disable certain functions for security reasons.
; It receives a comma-delimited list of function names. This directive is
; *NOT* affected by whether Safe Mode is turned On or Off.
; http://www.php.net/manual/en/ini.sect.safe-mode.php#ini.disable-functions
disable_functions =
make sure that exec is not listed like this:
disable_functions=exec
If so, remove it and restart the apache.
For easy debugging I usually like to execute the php file manually (Can request more errors without setting it in the main ini). to do so add the header:
#!/usr/bin/php
ini_set("display_errors", 1);
ini_set("track_errors", 1);
ini_set("html_errors", 1);
error_reporting(E_ALL);
to the beginning of the file, give it permissions using chmod +x myscript.php and execute it ./myscript.php. It's very heedful especially on a busy server that write a lot to the log file.
EDIT
Sounds like a permissions issue. Create a bash script that does something simple as echo "helo world" and try to run it. Make sure you have permissions for the file and for the folder containing the file. you chould just do chmod 755 just for testing.

A few more notes
For debugging always wrap your exec/shell_exec function in var_dump().
error_reporting(-1); should be on, as should be display_errors, as last resort even set_error_handler("var_dump"); - if only to see if PHP itself didn't invoke execvp or else.
Use 2>&1 (merge the shells STDERR to STDOUT stream) to see why an invocation fails.
For some cases you may need to wrap your command in an additional shell invocation:
// capture STDERR stream via standard shell
echo shell_exec("/bin/sh -c 'ffmpeg -opts 2>&1' ");
Else the log file redirect as advised by #Mike is the most recommendable approach.
Alternate between the various exec functions to uncover error messages otherwise. While they mostly do the same thing, the output return paths vary:
exec() → either returns the output as function result, or through the optional $output paramater.
Also provides a $return_var parameter, which contains the errno / exit code of the run application or shell. You might get:
ENOENT (2) - No such file
EIO (127) - IO error: file not found
// run command, conjoined stderr, output + error number
var_dump(exec("ffmpeg -h 2>&1", $output, $errno), $output, $errno));
shell_exec() → is what you want to run mostly for shell-style expressions.
Be sure to assign/print the return value with e.g. var_dump(shell_exec("..."));
`` inline backticks → are identical to shell_exec.
system() → is similar to exec, but always returns the output as function result (print it out!). Additionally allows to capture the result code.
passthru() → is another exec alternative, but always sends any STDOUT results to PHPs output buffer. Which oftentimes makes it the most fitting exec wrapper.
popen() or better proc_open() → allow to individually capture STDOUT and STDERR.
Most shell errors wind up in PHPs or Apaches error.log when not redirected. Check your syslog or Apache log if nothing yields useful error messages.
Most common issues
As mentioned by #Kuf: for outdated webhosting plans, you could still find safe_mode or disable_functions enabled. None of the PHP exec functions will work. (Best to find a better provider, else investigate "CGI" - but do not install your own PHP interpreter while unversed.)
Likewise can AppArmor / SELinux / Firejail sometimes be in place. Those limit each applications ability to spawn new processes.
The intended binary does not exist. Pretty much no webhost does have tools like ffmpeg preinstalled. You can't just run arbitrary shell commands without preparation. Some things need to be installed!
// Check if `ffmpeg` is actually there:
var_dump(shell_exec("which ffmpeg"));
The PATH is off. If you installed custom tools, you will need to ensure they're reachable. Using var_dump(shell_exec("ffmpeg -opts")) will search all common paths - or as Apache has been told/constrained (often just /bin:/usr/bin).
Check with print_r($_SERVER); what your PATH contains and if that covers the tool you wanted to run. Else you may need to adapt the server settings (/etc/apache2/envvars), or use full paths:
// run with absolute paths to binary
var_dump(shell_exec("/bin/sh -c '/usr/local/bin/ffmpeg -opts 2>&1'"));
This is somewhat subverting the shell concept. Personally I don't think this preferrable. It does make sense for security purposes though; moreover for utilizing a custom installation of course.
Permissions
In order to run a binary on BSD/Linux system, it needs to be made "executable". This is what chmod a+x ffmpeg does.
Furthermode the path to such custom binaries needs to be readable by the Apache user, which your PHP scripts run under.
More contemporary setups use PHPs builtin FPM mode (suexec+FastCGI), where your webhosting account equals what PHP runs with.
Test with SSH. It should go without saying, but before running commands through PHP, testing it in a real shell would be highly sensible. Probe with e.g. ldd ffmpeg if all lib dependencies are there, and if it works otherwise.
Use namei -m /Usr/local/bin/ffmpeg to probe the whole path, if unsure where any access permission issues might arise from.
Input values (GET, POST, FILE names, user data) that get passed as command arguments in exec strings need to be escaped with escapeshellarg().
$q = "escapeshellarg";
var_dump(shell_exec("echo {$q($_GET['text'])} | wc"));
Otherwise you'll get shell syntax errors easily; and probably exploit code installed later on...
Take care not to combine backticks with any of the *exec() functions:
$null = shell_exec(`wc file.txt`);
↑ ↑
Backticks would run the command, and leave shell_exec with the output of the already ran command. Use normal quotes for wrapping the command parameter.
Also check in a shell session how the intended program works with a different account:
sudo -u www-data gpg -k
Notably for PHP-FPM setups test with the according user id. www-data/apache are mostly just used by olden mod_php setups.
Many cmdline tools depend on some per-user configuration. This test will often reveal what's missing.
You cannot get output for background-run processes started with … & or nohup …. In such cases you definitely need to use a log file redirect exec("cmd > log.txt 2>&1 &");
On Windows
CMD invocations will not play nice with STDERR streams often.
Definitely try a Powershell script to run any CLI apps else, or use a command line like:
system("powershell -Command 'pandoc 2>&1'");
Use full paths, and prefer forward slashes always ("C:/Program Files/Whatevs/run.exe" with additional quotes if paths contain spaces).
Forward slashes work on Windows too, ever since they were introduced in MS-DOS 2.0
Figure out which service and SAM account IIS/Apache and PHP runs as. Verify it has execute permissions.
You can't run GUI apps usually. (Typical workaround is the taskscheduler or WMI invocations.)
PHP → Python, Perl
If you're invoking another scripting interpreter from PHP, then utilize any available debugging means in case of failures:
passthru("PYTHONDEBUG=2 python -vvv script.py 2>&1");
passthru("perl -w script.pl 2>&1");
passthru("ruby -wT1 script.rb 2>&1");
Or perhaps even run with any syntax -c check option first.

Since you are dropping out of the PHP context into the native shell, you are going to have a lot of issues debugging.
The best and most foolproof I have used in the past is writing the output of the script to a log file and tailing it during PHP execution.
<?php
shell_exec("filename > ~/debug.log 2>&1");
Then in a separate shell:
tail -200f ~/debug.log
When you execute your PHP script, your errors and output from your shell call will display in your debug.log file.

You can retreive the outputs and return code of the exec commands, thoses might contains informations that would explain the problem...
exec('my command', $output, $return);

Command consolidation

I'm not sure what to tag this with, but I need help combining two commands into a single command. I've tried this with ant, but it doesn't perform as required (long story). Essentially I need
javac *.java
java org.junit.runner.JUnitCore filename
To be consolodated into a single command. Preferrably something like
ant
with an external build.xml file, however after several hours fiddling with Ant I've gotten it to work but not as required (I need continuous output to stdout during runtime). I'm fine with shell scripts, clever java tricks, anything. I'll take what I can get at this point.

Writing a shell script is really a trivial matter: just copy-paste those exact two lines into a file (say you call it myscript.sh) and you're done. Then you can run it with sh myscript.sh. For added convenience add a first line that says #!/bin/sh (the so-called "hash-bang" incantation), issue a chmod u+x myscript.sh, and then you can run it as any other command: ./myscript.sh.
BTW this turned out into a question unrelated to Java, you might retag it with a shell script-related tag.

How do I open a .bat containing a GUI in a java program in Linux?

everyone. I'm quite new here so please be tolerant if I make any mistakes.
I have a .bat file containing a command line to open up a .jar file that contains a program that has a GUI in it. The only line that's in the .bat file is:
java -jar "NewServer.jar"
I've been trying to use Runtime() to get this to run, but most the instructions I find to open a .bat file in a java program are for Windows. I'm currently using Fedora 12 (don't tell me to upgrade, I can't) if that makes a difference and programming using Eclipse. I also found this ProcessBuilder thing, but I couldn't get it to work so unless you have very explicit directions on how to use it, please don't include it in your answer. I would much rather use Runtime. It looked simpler.
Here's my code to test using Runtime in a java program. I'm hoping that if I can get this to work, I can get it to work in my real program.
import java.io.IOException;
public class testbat {
public static void main(String[] args) {
Process proc = null;
try {
proc = Runtime.getRuntime().exec("./ myServer.bat");
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Cool");
}
The last line is just there for me to see if the program actually ran in case the GUI doesn't open. Also, I've already tried many combinations of things to include in the area after ".exec". I've tried using a path like "~/user/workspace/ProjectServer/dist/myServer.bat" to no avail.
I also already know that .bat files are for windows, but I'm able to execute it in linux, so I don't know if that makes a difference. I also tried using a .sh file the same way and it didn't work.
Please bear in mind that I'm not that great at Java, but I had to use it for this particular program, so if your answers could be really descriptive that would be awesome.

Just take that line out of the bat file, and run it. Yo're making it too hard.
$ java -jar "NewServer.jar"
will work. The quotes aren't necessary, so
$ java -jar NewServer.jar
will work as well. If you want to have the equivalent of your bat file, create a file named, say, run_newserver containing that line. Change its mode to executable:
$ cat > run_newserver
java -jar NewServer.jar
^D
$ chmod a+x run_newserver
$ ./run_newserver
Ideally, since you shouldn't have scripts without comments, do this. In your favorite editor, create a file run_newserver containing
#!/usr/bin/env bash
java -jar NewServer.jar
and chmod that. The line with #! -- often called a "shebang line" -- is UNIX magic that lets you say what interpreter you want. The program env in usr/bin finds your program and runs it (needed because different systems put bash in different directories.)
You could even put explanatory comments in the file too.
I'm a little unclear why you want to use Runtime#exec to run it at all -- it seems you'll just need a shell script to start that program.

Why are you using Java to run a Batch file, that in turn runs a Java program? Why have Batch in the loop at all? Just put the jar in your classpath and call it directly.

Batch (.bat) files are only for Windows environment. So, Try using shell script
Process proc = Runtime.getRuntime().exec("myServer.sh");

Just open up terminal and do this
vi /dir/to/exec/exec.sh
tap "i" and write this
#!/bin/sh
java -jar "NewServer.jar"
or if you want to run it in the background
#!/bin/sh
java -jar "NewServer.jar" & > /tmp/JavaServer.log
hit esc and type ":wq" and you have saved the file.
type this into the terminal
chmod +x /dir/to/exec/exec.sh
this give executable privileges and then you should run the file like
sh /dir/to/exec/exec.sh

Process is only initialized by your first call. You need to run:
proc.waitfor();
to get it to actually run your app.

Java ProcessBuilder showing console of started java application?

I have a JAVA application that launches (using ProcessBuilder) another JAVA application like this:
String val = "something";
ProcessBuilder processBuilder = new ProcessBuilder("java", "-classpath", dir, appName, val);
Process p = processBuilder.start();
Now, this works fine, appName is launched with the parameter val and it runs and works ... great ... the problem is no Console Window appears ... appName does a LOT of outputting to the console and we need to see it ... how can I start the process with a console?
I am trying stuff like ("CMD.exe", "java", "-classpath", dir, appName, val), etc... but I can't get it right ...
Also, I can't redirect the streams, my program can actually start 5-10 of these appName's, each should have their own console window showing their own information.
Any help would be much appreciated.
Thanks,

console windows are generally not the most reliable form of logging. they only store a set amount of information (buffer) and can behave differently across platforms.
i strongly suggest logging to a file using something like log4j and if you need to see it real time use a tail like program (i see you're using windows).
in addition to this, seeing as you want the windows visible at all times and launching a tail program for each log might be annoying, i'd write my own log window in java swing.
the basic idea is to not rely on the OS too much.

Tried Runtime.getRuntime().exec("cscript java -classpath ..."); ?
Anyway, consider using a logging framwork (log4j, commons-logging), because opening 5 consoles is not the most clever thing to do.

I call a few shell scripts via Process to open a command line window and launch whatever I need. As long as the scripts don't detach - you can usually stop any shell command from doing this -java will still hold the running process.
I did it in linux but the concept should be similar.
#!/bin/bash
# To open a process in a new window.
gnome-terminal -x ./your-real-shell-script-here.sh "$#"
the real script will have your java execution in it, such as:
#!/bin/bash
java -jar your-jar-file.jar "$#"
I think you can use javaw to run on windows, so you might only need the one shell script.

A Console object only exists when you execute java.... from a console. Otherwise, the call to obtain one returns null.
If you want to see a console, you need to open a command shell console (e.g. windows cmd.exe or Unix bash shell window) and type:
java -classpath="..." com.example.appName arg1
If you want to run in a different manner, sorry to say, logging to Console is not for you. Instead, log using one of:
log4j
slf4j
logback