capture_all: Run an R expression and capture output and messages in a...
In svMisc: 'SciViews' - Miscellaneous Functions

Description Usage Arguments Value Note See Also Examples

This function captures results of evaluating one or several R expressions the same way as it would be issued at the prompt in a R console. The result is returned in a character string. Errors, warnings and other conditions are treated as usual, including the delayed display of the warnings if options(warn = 0).

capture_all(expr, split = TRUE, echo = TRUE, file = NULL, markStdErr = FALSE)

captureAll(expr, split = TRUE, echo = TRUE, file = NULL, markStdErr = FALSE)

warnings2(...)

`expr`	A valid R expression to evaluate (names and calls are also accepted).
`split`	Do we split output, that is, do we also issue it at the R console too, or do we only capture it silently?
`echo`	Do we echo each expression in front of the results (like in the console)? In case the expression spans on more than 7 lines, only first and last three lines are echoed, separated by `[...]`.
`file`	A file, or a valid opened connection where output is sunk. It is closed at the end, and the function returns `NULL` in this case. If `file = NULL` (by default), a `textConnection()` captures the output and it is returned as a character string by the function.
`markStdErr`	If `TRUE`, stderr is separated from sddout by STX/ETX characters.
`...`	Items passed directly to `warnings2()`.

Returns a string with the result of the evaluation done in the user workspace.

If the expression is provided as a character string that should be evaluated, and you need a similar behavior as at the prompt for incomplete lines of code (that is, to prompt for more), you should not parse the expression with parse(text = "<some_code>") because it returns an error instead of an indication of an incomplete code line. Use parse_text("<some_code>") instead, like in the examples bellow. Of course, you have to deal with incomplete line management in your GUI/CLI application... the function only returns NA instead of a character string. Starting from version 1.1.3, .Traceback is not set any more in the base environment, but it is .Traceback_capture_all that is set in temp_env(). You can get its value with get_temp(".Traceback_capture_all"). Also, if there are many warnings, those are now assigned in temp_env() instead of baseenv(). Consequently, they cannot be viewer with warnings() but use warnings2() in this case.

parse(), expression(), capture.output()

writeLines(capture_all(expression(1 + 1), split = FALSE))
writeLines(capture_all(expression(1 + 1), split = TRUE))
writeLines(capture_all(parse_text("search()"), split = FALSE))
## Not run: 
writeLines(capture_all(parse_text('1:2 + 1:3'), split = FALSE))
writeLines(capture_all(parse_text("badname"), split = FALSE))

## End(Not run)

# Management of incomplete lines
capt_res <- capture_all(parse_text("1 +")) # Clearly an incomplete command
if (is.na(capt_res)) cat("Incomplete line!\n") else writeLines(capt_res)
rm(capt_res)

Attaching package: ‘svMisc’

The following object is masked from ‘package:utils’:

    ?

:> 1 + 1
[1] 2

:> 1 + 1
[1] 2
:> 1 + 1
[1] 2

:> search()
 [1] ".GlobalEnv"        "package:svMisc"    "package:stats"    
 [4] "package:graphics"  "package:grDevices" "package:utils"    
 [7] "package:datasets"  "package:methods"   "Autoloads"        
[10] "package:base"     

:> 1:2 + 1:3
[1] 2 4 4
Warning message:
In 1:2 + 1:3 : longer object length is not a multiple of shorter object length

:> badname
Error: object 'badname' not found

Incomplete line!