base (version 3.5.1)

file.show: Display One or More Text Files

Description

Display one or more (plain) text files, in a platform specific way, typically via a ‘pager’.

Usage

file.show(…, header = rep("", nfiles),
          title = "R Information",
          delete.file = FALSE, pager = getOption("pager"),
          encoding = "")

Arguments

…

one or more character vectors containing the names of the files to be displayed. Paths with have tilde expansion.

header

character vector (of the same length as the number of files specified in …) giving a header for each file being displayed. Defaults to empty strings.

title

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.

delete.file

should the files be deleted after display? Used for temporary files.

pager

the pager to be used: not used on all platforms

encoding

character string giving the encoding to be assumed for the file(s).

Details

This function provides the core of the R help system, but it can be used for other purposes as well, such as page.

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 "internal" and "console" on Windows), or by letting pager be an R function which will be called with arguments (files, header, title, delete.file) corresponding to the first four arguments of file.show and take care of interfacing to the GUI.

The R.app GUI on macOS uses its internal pager irrespective of the setting of pager.

Not all implementations will honour delete.file. In particular, using an external pager on Windows does not, as there is no way to know when the external application has finished with the file.

See Also

files, list.files, help; RShowDoc call file.show() for type = "text". Consider getOption("pdfviewer") and e.g., system for displaying pdf files.

file.edit.

Examples

# NOT RUN {
file.show(file.path(R.home("doc"), "COPYRIGHTS"))
# }