Unix is a multi-user, multi-tasking operating system that was initially developed by Bell Labs in the 1970s. Various similar operating systems that are POSIX compliant (ie compatible with Unix) have since been developed (POSIX is an abbreviation for Portable Operating System Interface for UNIX). These include the following: the BSD family (OpenBSD, FreeBSD, NetBSD, Mac OS/X), Solaris, IRIX, AIX, SunOS, UnixWare, OpenServer and Linux.
Software written for POSIX compliant operating systems is generally able to be compiled for all POSIX platforms with little or no platform-specific changes. This makes the commands and utilities available for this extended family of operating systems very similar, and there are few differences between administering them.
The articles in this section are about useful command line utilities and commonly used application software on POSIX compliant operating systems. For Mac OSX specific articles see my OSX section.
I recently posted a Subversion Command Line Script to export changed files and in response to a comment on that page have posted a new version here, which writes out the current revision number to a file and only exports from that revision when the script is run again.
If you are connecting to a remote server from the Mac OS X terminal and get the message "Error opening terminal: xterm-color" when doing certain operations on the remote server, then you either change your terminal’s declaration setting or add a TERM declaration to the bash profile on the server at the other end to prevent the error message from happening. There may be other ways to solve it at the server end but this post shows a quick and easy fix.
Sometimes a script may need to only be run as root or using sudo, or run ensuring that it is not being run by root or using sudo. This quick post shows how to check if it’s the root user and exit the script.
A couple of days ago I posted how to export just the added/modified files from a subversion repository between two revisions using TortoiseSVN, the Windows Explorer SVN plugin. This post has a command line script which is used to achieve the same thing and means it can be run from UNIX based systems from the CLI.
This post is more of a reference for myself rather than anything else to solve an issue I was having with DNS lookups on a CentOS machine. It’s how to prevent the /etc/resolv.conf file being overwritten when the system restarts if you have a custom configuration you don’t want changed.
There may be times when you need to know the actual location a BASH script is located within the script. This can be done with a combination of the $0 value and the dirname command.