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<HTML
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>system</TITLE
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><H1
><A
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>system</A
></H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN32107"
></A
><P
> (PHP3 , PHP4 )</P
>system -- Execute an external program and display output</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN32110"
></A
><H2
>Description</H2
><DIV
CLASS="funcsynopsis"
><A
NAME="AEN32112"
></A
><P
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>string <B
CLASS="function"
>system</B
></CODE
> (string command [, int
return_var])</CODE
></P
><P
></P
></DIV
><P
> <B
CLASS="function"
>System()</B
> is just like the C version of the
function in that it executes the given
<TT
CLASS="parameter"
><I
>command</I
></TT
> and outputs the result. If a
variable is provided as the second argument, then the return
status code of the executed command will be written to this
variable.
</P
><P
> Note, that if you are going to allow data coming from user input
to be passed to this function, then you should be using the
<B
CLASS="function"
>EscapeShellCmd()</B
> function to make sure that
users cannot trick the system into executing arbitrary
commands.
</P
><P
> Note also that 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.
</P
><P
> The <B
CLASS="function"
>System()</B
> 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.
</P
><P
> Returns the last line of the command output on success, and false
on failure.
</P
><P
> If you need to execute a command and have all the data from the
command passed directly back without any interference, use the
<B
CLASS="function"
>PassThru()</B
> function.
</P
><P
> See also <A
HREF="function.exec.html"
><B
CLASS="function"
>exec()</B
></A
>,
<B
CLASS="function"
>PassThru()</B
>, <A
HREF="function.popen.html"
><B
CLASS="function"
>popen()</B
></A
>,
<B
CLASS="function"
>EscapeShellCmd()</B
>, and the <A
HREF="language.operators.execution.html"
>backtick operator</A
>.
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