How do I read environment variables with sed?
4.8.1. – on Unix platforms In Unix, environment variables are words which begin with a dollar sign, such as $TERM, $HOME, $user, or $path. In sed, the dollar sign is used to indicate the last line of the input file, the end of a line (in the LHS), or a literal symbol (in the RHS). Sed cannot access variables directly, so one must pay attention to shell quoting requirements to expand the variables properly. To ALLOW the Unix shell to interpret the dollar sign (replacing it with an environment variable), put the script in double quotes: sed “s/_terminal-type_/$TERM/g” input.file >output.file To PREVENT the Unix shell from interpreting the dollar sign (letting sed define its meaning), put the script in single quotes: sed ‘s/.$//’ DOS.file >Unix.file To use BOTH Unix $environment_vars and sed /end-of-line$/ pattern matching, use single quotes to bracket the sed part ‘like so’, then follow immediately with double quotes “$HERE” when you want the shell to substitute the variable, and resume
