Help understanding what this ls -l command is checking in a script
Hello,
we have a script that has the two following lines:
I can't understand what these two lines are doing?
When I execute the first line nothing is output. I get that the command is being directed somewhere that is not shown. And when I execute the echo $? line I get a number. Not sure what this number means though? Is this command checking if I can successfully login to this server or not?
Also, is there a way to concatenate the two lines into one command line instruction to return the value?
Thank you.
Last edited by jim mcnamara; 10-09-2019 at 07:37 PM..
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Discussion started by: netrom
5 Replies
LEARN ABOUT PHP
system
SYSTEM(3) 1 SYSTEM(3)system - Execute an external program and display the outputSYNOPSIS
string system (string $command, [int &$return_var])
DESCRIPTION system(3) is just like the C version of the function in that it executes the given $command and outputs the result.
The system(3) call also tries to automatically flush the web server's output buffer after each line of output if PHP is running as a
server module.
If you need to execute a command and have all the data from the command passed directly back without any interference, use the passthru(3)
function.
PARAMETERS
o $command
- The command that will be executed.
o $return_var
- If the $return_var argument is present, then the return status of the executed command will be written to this variable.
RETURN VALUES
Returns the last line of the command output on success, and FALSE on failure.
EXAMPLES
Example #1
system(3) example
<?php
echo '<pre>';
// Outputs all the result of shellcommand "ls", and returns
// the last output line into $last_line. Stores the return value
// of the shell command in $retval.
$last_line = system('ls', $retval);
// Printing additional info
echo '
</pre>
<hr />Last line of the output: ' . $last_line . '
<hr />Return value: ' . $retval;
?>
NOTES
Warning
When allowing user-supplied data to be passed to this function, use escapeshellarg(3) or escapeshellcmd(3) to ensure that users can-
not trick the system into executing arbitrary commands.
Note
If a program is started with this function, in order for it to continue running in the background, the output of the program must be
redirected to a file or another output stream. Failing to do so will cause PHP to hang until the execution of the program ends.
Note
When safe mode is enabled, you can only execute files within the safe_mode_exec_dir. For practical reasons, it is currently not
allowed to have .. components in the path to the executable.
Warning
With safe mode enabled, the command string is escaped with escapeshellcmd(3). Thus, echo y | echo x becomes echo y | echo x.
SEE ALSO exec(3), passthru(3), popen(3), escapeshellcmd(3), pcntl_exec(3), backtick operator.
PHP Documentation Group SYSTEM(3)