The problem that the return value of PHP's exec cannot be a negative number in Linux_PHP Tutorial

There is no problem with the exec function in Windows environment, but the return value cannot be negative in Linux.

string exec ( string $command [, array &$output [, int &$return_var ]] )

The third parameter, why can’t it receive negative numbers??
The &$return_var here is the program return value. At first, my answer was that it can be a negative number.
Generally in C language we would write like this

The code is as follows

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代码如下	复制代码
#include #include int main() {     printf("^_^n");     return -5; }

#include

#include
int main()
{

Printf("^_^n");

Return -5;

}

代码如下	复制代码
E:devphp535>php -r "exec('return.exe',$out,$a);var_dump($a);" int(-2)

This -5 is the return value, but it is customary to write it as 0 or 1.

Note: Many people write the main function as void main() in their C code. This is actually wrong, so I won’t go into details.

代码如下	复制代码
exec("/home/wwwroot/test/rtest.out 2>&1",$out,$a); var_dump($out,$a); array(1) { [0]=> string(3) "^_^" } int(251)

After compiling the above code, run it under CMD, and then you can see the output result. Then, enter "echo %ERRORLEVEL%", press Enter, and you can see the return value of the program. This %ERRORLEVEL% represents the return status of the program. It is indeed possible to be a negative number under WIN. As shown in the picture:

, php calls are also normal.

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E:devphp535>php -r "exec( 'return.exe',$out,$a);var_dump($a);" int(-2)

代码如下

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-bash-3.00$ vi main.c -bash-3.00$ gcc -o ./mm main.c -bash-3.00$ ll total 48 drwxr-xr-x  3 www www 4096 May  4  2011 2011 drwxr-xr-x  6 www www 4096 Jun 23  2011 eoc -rwxr-xr-x  1 www www 7131 Feb  1 12:47 hello -rw-r--r--  1 www www    3 Feb  1 12:51 hello.c -rw-r--r--  1 www www   99 Feb  1 12:50 main.c -rwxr-xr-x  1 www www 4714 Feb  1 12:51 mm drwxr-xr-x  3 www www 4096 Jun 24  2011 test -bash-3.00$ ./mm ^_^ -bash-3.00$ echo $? 251 -bash-3.00$

But under Linux, it is always a positive number. At first I suspected it was a permissions issue. After using chmod +x, the permissions issue was eliminated.

The code is as follows	Copy code
exec("/home/wwwroot/test/ rtest.out 2>&1",$out,$a); var_dump($out,$a); array(1) { [0]=> string(3) "^_^" } int(251)

It looks like 256+return val. You can see that a negative number is actually returned, but it is converted into a positive number. Then I looked at the source code in standard/exec.c, and found no clues. It was very strange, and suddenly I realized that I had forgotten a step. Forgot to look at the value returned by the program to the OS. You can use echo $? to display the status of the last command.

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-bash-3.00$ vi main.c -bash-3.00$ gcc -o ./mm main.c -bash-3.00$ ll total 48 drwxr-xr-x 3 www www 4096 May 4 2011 2011 drwxr-xr-x 6 www www 4096 Jun 23 2011 eoc -rwxr-xr-x 1 www www 7131 Feb 1 12:47 hello -rw-r--r-- 1 www www 3 Feb 1 12:51 hello.c -rw-r--r-- 1 www www 99 Feb 1 12:50 main.c -rwxr-xr-x 1 www www 4714 Feb 1 12:51 mm drwxr-xr-x 3 www www 4096 Jun 24 2011 test -bash-3.00$ ./mm ^_^ -bash-3.00$ echo $? 251 -bash-3.00$

This way you can see what value exec returns to the OS.
Under Linux, this return value is an unsigned type and returns a positive number, so it is also a positive number when passed to PHP. PHP is actually the value returned by the exec call.

exec directory operation

2down vote For greater control over how the child process will be executed, you can use the proc_open() function:

2 down vote

For greater control over how the child process will be executed, you can use the proc_open() function:

The code is as follows

代码如下

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$cmd  = 'Scripts/script.sh';  $cwd  = 'Scripts';    $spec = array(      // can something more portable be passed here instead of /dev/null?      0 => array('file', '/dev/null', 'r'),      1 => array('file', '/dev/null', 'w'),      2 => array('file', '/dev/null', 'w'),  );    $ph = proc_open($cmd, $spec, $pipes, $cwd);  if ($ph === FALSE) {      // open error  }    // If we are not passing /dev/null like above, we should close  // our ends of any pipes to signal that we're done. Otherwise  // the call to proc_close below may block indefinitely.  foreach ($pipes as $pipe) {      @fclose($pipe);  }    // will wait for the process to terminate  $exit_code = proc_close($ph);  if ($exit_code !== 0) {      // child error  }

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$cmd = 'Scripts/script.sh'; $cwd = 'Scripts';

$spec = array( // can something more portable be passed here instead of /dev/null? 0 => array('file', '/dev/null', 'r'), 1 => array('file', '/dev/null', 'w'), 2 => array('file', '/dev/null', 'w'), ); $ph = proc_open($cmd, $spec, $pipes, $cwd); if ($ph === FALSE) { // open error } // If we are not passing /dev/null like above, we should close

// our ends of any pipes to signal that we're done. Otherwise // the call to proc_close below may block indefinitely. foreach ($pipes as $pipe) {

@fclose($pipe);

} // will wait for the process to terminate $exit_code = proc_close($ph); if ($exit_code !== 0) { // child error } http://www.bkjia.com/PHPjc/632187.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632187.htmlTechArticleThere is no problem with the exec function in the Windows environment, but the return value cannot be a negative number in Linux. string exec ( string $command [, array $output [, int $return_var ]] ) The third parameter...