Skip to main content

Script - Standard in, out, and error -- Meaning of "> /dev/null 2>&1"


in your .vimrc:

    ./Script.sh 1>$LOGGER_BASE_PATH/Script_$CURRENTTIME.log 2>&1 &
    

Standard in, out, and error

There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it's an interactive program, or from another program if it's processing the other program's output. The program usuallyprints to standard output, and sometimes prints to standard error. These three file descriptors (you can think of them as "data pipes") are often called STDIN, STDOUT, and STDERR.

Sometimes they're not named, they're numbered! The built-in numberings for them are 0, 1, and 2, in that order. By default, if you don't name or number one explicitly, you're talking about STDOUT.

Given that context, you can see the command above is redirecting standard output into /dev/null, which is a place you can dump anything you don't want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this).

The short explanation, therefore, is "all output from this command should be shoved into a black hole." That's one good way to make a program be really quiet!

Comments

Popular posts from this blog

Zabbix History Table Clean Up

Zabbix history table gets really big, and if you are in a situation where you want to clean it up. Then we can do so, using the below steps. Stop zabbix server. Take table backup - just in case. Create a temporary table. Update the temporary table with data required, upto a specific date using epoch . Move old table to a different table name. Move updated (new temporary) table to original table which needs to be cleaned-up. Drop the old table. (Optional) Restart Zabbix Since this is not offical procedure, but it has worked for me so use it at your own risk. Here is another post which will help is reducing the size of history tables - http://zabbixzone.com/zabbix/history-and-trends/ Zabbix Version : Zabbix v2.4 Make sure MySql 5.1 is set with InnoDB as innodb_file_per_table=ON Step 1 Stop the Zabbix server sudo service zabbix-server stop Script. echo "------------------------------------------" echo " 1. Stopping Zabbix Server &quo

Access Filter in SSSD `ldap_access_filter` [SSSD Access denied / Permission denied ]

Access Filter Setup with SSSD ldap_access_filter (string) If using access_provider = ldap , this option is mandatory. It specifies an LDAP search filter criteria that must be met for the user to be granted access on this host. If access_provider = ldap and this option is not set, it will result in all users being denied access. Use access_provider = allow to change this default behaviour. Example: access_provider = ldap ldap_access_filter = memberOf=cn=allowed_user_groups,ou=Groups,dc=example,dc=com Prerequisites yum install sssd Single LDAP Group Under domain/default in /etc/sssd/sssd.conf add: access_provider = ldap ldap_access_filter = memberOf=cn=Group Name,ou=Groups,dc=example,dc=com Multiple LDAP Groups Under domain/default in /etc/sssd/sssd.conf add: access_provider = ldap ldap_access_filter = (|(memberOf=cn=System Adminstrators,ou=Groups,dc=example,dc=com)(memberOf=cn=Database Users,ou=Groups,dc=example,dc=com)) ldap_access_filter accepts standa

Installing Zabbix Version 2.4 Offline (Zabbix Server without Internet).

There might be situations where you have a remote/zabbix server which does not have internet connectivity, due to security or other reasons. So we create a custom repo on the remote/zabbix server so that we can install zabbix using rpms Here is how we are planning to do this. Download all the dependency rpms on a machine which has internet connection, using yum-downloadonly or repotrack . Transfer all the rpms to the remote server. Create a repo on the remote server. Update yum configuration. Install. NOTE: This method can be used to install any application, but here we have used zabbix as we had this requirement for a zabbix server. Download dependent rpms . On a machine which has internet connection install the package below. And download all the rpms . Make sure the system are similar (not required to be identical - At-least the OS should be of same version) mkdir /zabbix_rpms yum install yum-downloadonly Downloading all the rpms to location /zabbix_rpms/ ,