savehistory 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. When supplied, only unique matching lines are shown.
...	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. Notably, there are different implementations for Unix and Windows.

Windows:

The functions described here work in Rgui and interactive Rterm but not in batch use of Rterm nor in embedded/DCOM versions.

Unix-alikes:

The functions described here work under the readline command-line interface but may not otherwise (for example, in batch use or in an embedded application). Note that R can be built without readline.

R.app, the console on macOS, has a separate and largely incompatible history mechanism, which by default uses a file ‘.Rapp.history’ and saves up to 250 entries. These functions are not currently implemented there.

The (readline on Unix-alikes) history mechanism is controlled by two environment variables: R_HISTSIZE controls the number of lines that are saved (default 512), and R_HISTFILE (default ‘.Rhistory’) sets the filename used for the loading/saving of history if requested at the beginning/end of a session (but not the default for loadhistory/savehistory). 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 environment variables are read at the time of saving, so can be altered within a session by the use of Sys.setenv.

On Unix-alikes: Note that readline history library saves files with permission 0600, that is with read/write permission for the user and not even read permission for any other account.

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 only the console message is printed.

Note

If you want to save the history at the end of (almost) every interactive session (even those in which you do not save the workspace), you can put a call to savehistory() in .Last. See the examples.

Examples

## Not run: 
## Save the history in the home directory: note that it is not
## (by default) read from there but from the current directory
.Last <- function()
    if(interactive()) try(savehistory("~/.Rhistory"))

## End(Not run)