Display one or more (plain) text files, in a platform specific way, typically via a ‘pager’.
file.show(…, header = rep("", nfiles),
title = "R Information",
delete.file = FALSE, pager = getOption("pager"),
encoding = "")
one or more character vectors containing the names of the files to be displayed. Paths with have tilde expansion.
character vector (of the same length as the number of files
…) giving a header for each file being
displayed. Defaults to empty strings.
an overall title for the display. If a single separate
window is used for the display,
title will be used as the window
title. If multiple windows are used, their titles should combine the title
and the file-specific header.
should the files be deleted after display? Used for temporary files.
the pager to be used: not used on all platforms
character string giving the encoding to be assumed for the file(s).
This function provides the core of the R help system, but it can be
used for other purposes as well, such as
How the pager is implemented is highly system-dependent.
The basic Unix version concatenates the files (using the headers) to a
temporary file, and displays it in the pager selected by the
pager argument, which is a character vector specifying a system
command (a full path or a command found on the
PATH) to run on
the set of files. The ‘factory-fresh’ default is to use
R_HOME/bin/pager, which is a shell script running the command-line
specified by the environment variable
PAGER whose default is set
at configuration, usually to
less. On a Unix-alike
more is used if
pager is empty.
Most GUI systems will use a separate pager window for each file, and
let the user leave it up while R continues running. The selection of
such pagers could either be done using special pager names being
intercepted by lower-level code (such as
"console" on Windows), or by letting
pager be an R
function which will be called with arguments
title, delete.file) corresponding to the first four arguments of
file.show and take care of interfacing to the GUI.
R.app GUI on macOS uses its internal pager irrespective
of the setting of
Not all implementations will honour
particular, using an external pager on Windows does not, as there is
no way to know when the external application has finished with the