set_lowest_fd()

Specify the lowest acceptable file descriptor

Synopsis:

#include <fcntl.h>

int set_lowest_fd( int fd );

Since:

BlackBerry 10.0.0

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Arguments:

fd
The minimum file descriptor that you want to get.

Description:

The set_lowest_fd() function sets the lowest file descriptor number that will be returned by open(), pipe(), and other functions that return file descriptors. A process with the setuid/setgid file permission bit set can use this function at the begining of main() to ensure that it never unexpectedly gets back a file descriptor equal to 0, 1, or 2, which malicious programmers sometimes cause to happen by closing stdin, stdout, or stderr before spawning the process.

This function doesn't affect dup and dup2 because they're primarily used to set file descriptors 0, 1, and 2 for file-redirection purposes.

Returns:

The previous lowest number (0 for the first time it's called).

Classification:

QNX Neutrino

Safety:  
Cancellation point No
Interrupt handler No
Signal handler No
Thread No

Last modified: 2014-06-24



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