on.exit records the expression given as its argument as needing to be executed when the current function exits (either naturally or as the result of an error). This is useful for resetting graphical parameters or performing other cleanup actions.
on.exit(expr = NULL, add = FALSE)
- an expression to be executed.
- if TRUE, add
exprto be executed after any previously set expressions; otherwise (the default)
exprwill overwrite any previously set expressions.
expr was evaluated changed in R 2.8.0, and the following applies only to that and later versions.
expr argument passed to
on.exit is recorded without evaluation. If it is not subsequently removed/replaced by another
on.exit call in the same function, it is evaluated in the evaluation frame of the function when it exits (including during standard error handling). Thus any functions or variables in the expression will be looked for in the function and its environment at the time of exit: to capture the current value in
substitute or similar. This is a ‘special’ primitive function: it only evaluates the argument
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
Documentation reproduced from R 2.15.3. License: GPL-2.