passthru
(PHP 3, PHP 4 )
passthru -- Execute an external program and display raw
output
Description
void passthru ( string command [, int return_var])
The passthru() function is similar to the exec() function
in that it executes a command. If the return_var argument
is present, the return status of the Unix command will be
placed here. This function should be used in place of exec()
or system() when the output from the Unix command is binary
data which needs to be passed directly back to the browser.
A common use for this is to execute something like the pbmplus
utilities that can output an image stream directly. By setting
the Content-type to image/gif and then calling a pbmplus
program to output a gif, you can create PHP scripts that
output images directly.
Warning
If you are going to allow data coming from user input to
be passed to this function, then you should be using escapeshellarg()
or escapeshellcmd() to make sure that users cannot trick
the system into executing arbitrary commands.
Note: If you start a program using this function and want
to leave it running in the background, you have to make
sure that the output of that program is redirected to a
file or some other output stream or else PHP will hang until
the execution of the program ends.
Note: When safe mode is enabled, you can only execute executables
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, all words following the initial
command string are treated as a single argument. Thus, echo
y | echo x becomes echo "y | echo x".
See also exec(), system(), popen(), escapeshellcmd(), and
the backtick operator.
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