The Standard UNIX File Descriptors – Standard Input (stdin), Standard Output (stdout), and Standard Error (stderr). Bash and other modern shell provides I/O redirection facility. There are 3 default standard files (standard streams) open:
[a] stdin – Use to get input (keyboard) i.e. data going into a program.
[b] stdout – Use to write information (screen)
[c] stderr – Use to write error message (screen)
You can look at /usr/include/unistd.h if you forget them:
/* Standard file descriptors. */
#define STDIN_FILENO 0 /* Standard input. */
#define STDOUT_FILENO 1 /* Standard output. */
#define STDERR_FILENO 2 /* Standard error output. */
Here are 2 easy steps to ssh into a host without login:
One of the tools in any system engineer’s hand as well as those dealing with customer remote service is to set a remote connection to the other end’s server or PC, through VPN, Public IP or any other possible way. One easy yet effective approach is to establish a ssh tunnel by means of reverse SSH.
Here is the simple postfix configuration to make it work with freepbx.
Based on a customer request, we needed to have some virtual extensions (Voice Mail enabled) but the problem was that they wanted the incoming calls to extensions to ring 4 times before falling back to voice mail. Since by default FreePBX will get the extension status as UNAVAILABLE and I couldn’t get virtual extension running with this version of freepbx, i did this trick:
This post shows a plain CLID popup.
download the zipped files
Here is a step by step guide to create an H323 trunk from Asterisk to Cisco Call Manager (CCM)
In an environment with old LAN cabling, chances are so high that call get interrupted, words drop every now and then, and at the worst case, the sound quality gets terribly unbearable. This is mainly caused by the issue commonly referred to as Jitter.
After the DAHDI drivers have been loaded execute the following command on the Linux shell to check if the VPMADT032 is installed and operational.
Using fxotune will help echo canceller to work better.
Do this before setting up echo canceller, it means to disable echo canceller options in /etc/dahdi/system.conf and
/etc/asterisk/chan_dahdi.conf, and to stop asterisk but dahdi still running.