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The importas program

importas replaces a literal with the value of an environment variable, then executes another program.

Interface

     importas [ -i | -D default ] [ -u ] [ -s ] [ -C | -c ] [ -N | -n ] [ -d delim ] variable envvar prog...
     importas -S [ -i | -D default ] [ -u ] [ -s ] [ -C | -c ] [ -N | -n ] [ -d delim ] envvar prog...

• importas fetches the value of envvar in the environment. If neither the -D nor the -i option is given, and envvar is undefined, no word is returned (that is different from the empty word).
• importas then performs variable substitution on prog..., with variable as key and that string as value.
• importas then execs into the modified prog....

Options

• -D default : If this option is given and envvar is undefined, substitute default for the value of variable instead of no word. For instance, to substitute the empty word, use -D "".
• -i : Insist. If envvar is undefined, importas will not do anything; instead, it will exit 100 with an error message. This has precedence over any -D option.
• -u : Unexport. envvar will be removed from the environment after the substitution. importas -u variable envvar is equivalent to importas variable envvar unexport envvar.
• -S : import with same name. This option allows variable to be omitted; it will be the same as envvar. In other words, importas -S var is the same as importas var var.
• Other options are used to control the substitution mechanism.

Notes

• When envvar is undefined, and the -D option is not given, any variable substitution with variable as the key will return no word; that is true even when the ${variable} form to be substituted happens in the middle of a word (with a prefix and/or a postfix), which means the whole word will be deleted. If this is not the behaviour you want, use the -D option.