Difference between revisions of "Configuration how-to"

Latest revision as of 00:12, 5 January 2012

Loading Remote Environment Variables for a Synchronized Project

• An environment variable is a named value associated with a terminal session. Values take the form of strings, but numeric values can be stored and manipulated as strings.
• Environment variables are local to a terminal session; thus, if you change a variable in a terminal session, its changes affect only that terminal session. They are, however, inherited by child processes. Child processes cannot change environment variables associated with the parent.
• Two important environment variables important:
  • PATH: paths to binary files. If you have installed software in user space, make sure you update your $PATH to include the path to those binaries; then you can call them from anywhere.
  • LD_LIBRARY_PATH: paths to shared libraries. If an application in your $PATH uses shared libraries not within $LD_LIBRARY_PATH, you'll need to set $LD_LIBRARY_PATH to include them. Otherwise you will get an error such as: "libsomething.so: could not find shared library"

• The command for defining an environment variable is export VAR=VALUE, where VAR is the name of the environment variable and VALUE is the value.
• After definition, environment variables may be referenced as $VAR, with a dollar sign ($) before the variable name. E.g. echo $VAR following the above definition will print VALUE.
• E.g.:
  • export GREETING="Hello"
  • export PATH=$PATH:$HOME/bin
• Environment variables can be set per session on the command line, but are not stored. To store them, one may define them in ~/.bashrc or ~/.profile so that they load on startup (the files ~/.bashrc and ~/.profile contain instructions which execute upon startup of a terminal session). If you change ~/.bashrc or ~/.profile and want to start a new session with its changes, use the command source [filename], as in source ~/.bashrc or source ~/.profile. If you are not using bash, then you will need to change the shell-specific configuration.
• Make sure the relevant environment variables are set on the proper machine (the machine to compile or execute the binary).

• Alternatively, environment variables may be set in the Environment tab lib.path.jpg within a run configuration.