savehistory {utils}

R Documentation

Load or Save or Display the Commands History

Description

Load or save or display the commands history.

Usage

loadhistory(file = ".Rhistory")
savehistory(file = ".Rhistory")

history(max.show = 25, reverse = FALSE, pattern, ...)

timestamp(stamp = date(),
          prefix = "##------ ", suffix = " ------##",
          quiet = FALSE)

Arguments

file	The name of the file in which to save the history, or from which to load it. The path is relative to the current working directory.
max.show	The maximum number of lines to show. Inf will give all of the currently available history.
reverse	logical. If true, the lines are shown in reverse order. Note: this is not useful when there are continuation lines.
pattern	A character string to be matched against the lines of the history
...	Arguments to be passed to grep when doing the matching.
stamp	A value or vector of values to be written into the history.
prefix	A prefix to apply to each line.
suffix	A suffix to apply to each line.
quiet	If TRUE, suppress printing timestamp to the console.

Details

There are several history mechanisms available for the different R consoles, which work in similar but not identical ways. Other uses of R, in particular embedded uses, may have no history. This works under the readline command-line interface and the R.app Mac OS X console, but not otherwise (for example, in batch use or in an embedded application).

The readline history mechanism is controlled by two environment variables: R_HISTSIZE controls the number of lines that are saved (default 512), and R_HISTFILE sets the filename used for the loading/saving of history if requested at the beginning/end of a session (but not the default for these functions). There is no limit on the number of lines of history retained during a session, so setting R_HISTSIZE to a large value has no penalty unless a large file is actually generated.

These variables are read at the time of saving, so can be altered within a session by the use of Sys.setenv.

history shows only unique matching lines if pattern is supplied.

The timestamp function writes a timestamp (or other message) into the history and echos it to the console. On platforms that do not support a history mechanism (where the mechanism does not support timestamps) only the console message is printed.

Note

If you want to save the history at the end of (almost) every interactive session, you can put a call to savehistory() in .Last. See the examples.

Examples

## Not run: 
.Last <- function()
    if(interactive()) try(savehistory("~/.Rhistory"))

## End(Not run)

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