Php exec cannot return negative values in linux _ PHP Tutorial

Php exec cannot return negative values in linux. The exec function is normal in windows, but the return value cannot be negative in linux. Stringexec (string $ command [, array $ output [, int $ return_var]) The third exec function has no problem in windows, however, in linux, the return value cannot be negative.

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

In the third parameter, how can I not receive negative numbers ??
Here & $ return_var is the return value of the program. at first, my answer is a negative number.
We usually write this in c.

The code is as follows:
# Include # Include Int main () { Printf ("^_^ n "); Return-5; }

This-5 is the return value, but it is written as 0 or 1.
Note: Many people write the main function as void main () in C code. this is actually not correct, so I won't go into details.
Compile the above code and run it in CMD. then the output result is displayed. Enter "echo % ERRORLEVEL %" and press enter to view the program return value. This % ERRORLEVEL % indicates the return status of the program. It can be a negative number in WIN. :

, Php call is also normal.

The code is as follows:
E: devphp535> php-r "exec('return.exe ', $ out, $ a); var_dump ($ );" Int (-2)

However, in linux, it is always a positive number. it was initially suspected that it was a Permission problem. after chmod + x was used, the permission problem was ruled out.

The code is as follows:
Exec ("/home/wwwroot/test/rtest. out 2> & 1", $ out, $ ); Var_dump ($ out, $ ); Array (1) {[0] => string (3) "'''} int (251)

It seems to be 256 + return val. we can see that a negative number is actually returned, but it is converted to a positive number.
Then I read the source code in standard/exec. c, but I didn't find any clues. it was very strange. I suddenly thought I forgot a step. I forgot to read the OS value returned by the program.
Echo $? Displays the launch status of the last command.

The code is as follows:
-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 4096 May 4 2011 2011 Drwxr-xr-x 6 www 4096 Jun 23 2011 eoc -Rwxr-xr-x 1 www 7131 Feb 1 hello -Rw-r -- 1 www 3 Feb 1 :51 hello. c -Rw-r -- 1 www 99 Feb 1 :50 main. c -Rwxr-xr-x 1 www 4714 Feb 1mm Drwxr-xr-x 3 www 4096 Jun 24 2011 test -Bash-3.00 $./mm Pai_^ -Bash-3.00 $ echo $? 251 -Bash-3.00 $

In this way, you can see the value of exec returned to OS.
In linux, the returned value is of the unsigned type and returns a positive value. Therefore, it is also a positive value to pass to php. php is actually the value returned by the called exec.

Exec directory operations

2 down 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:

$ 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 shoshould close // Our ends of any pipes to signal that we're 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 }

Bytes. String exec (string $ command [, array $ output [, int $ return_var]) third parameter...