Variables

• Variables are essentially always strings, traditionally named in all caps, expanded with $ or ${}, and are set without $ at the start of a line:

  • SPAM=$HOME/mail/spam
  • mv $TENSPAM ${SPAM}.tmp
  • sa-learn --showdots --spam --mbox $SPAM.tmp
  • rm ${SPAM}.tmp

• Export command makes available to sub-programs, ie, "export SPAM=..." to set and export, or "export SPAM" to just export. Needed in ~/.bashrc, e.g. with PATH

• "set" and "env" commands list environment variables currently set; some already set like UID, HOME.

• Variables expanded within double-quotes, but not within single quoted strings (compare echo “$HOME” with echo '$HOME')

Notes: