R Under development (unstable) (2023-11-16 r85542 ucrt) -- "Unsuffered Consequences"
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> library("R.utils")
Loading required package: R.oo
Loading required package: R.methodsS3
R.methodsS3 v1.8.2 (2022-06-13 22:00:14 UTC) successfully loaded. See ?R.methodsS3 for help.
R.oo v1.25.0 (2022-06-12 02:20:02 UTC) successfully loaded. See ?R.oo for help.

Attaching package: 'R.oo'

The following object is masked from 'package:R.methodsS3':

    throw

The following objects are masked from 'package:methods':

    getClasses, getMethods

The following objects are masked from 'package:base':

    attach, detach, load, save

R.utils v2.12.3 successfully loaded. See ?R.utils for help.

Attaching package: 'R.utils'

The following object is masked from 'package:utils':

    timestamp

The following objects are masked from 'package:base':

    cat, commandArgs, getOption, isOpen, nullfile, parse, warnings

> 
> # Create files
> pathnames <- sapply(1:3, FUN=function(x) {
+   pathname <- tempfile()
+   cat(file=pathname, "Hello world!")
+   pathname
+ })
> 
> # Record checksums
> md5a <- sapply(pathnames, FUN=digest::digest, file=TRUE)
> 
> # Record current time stamps
> ta <- file.info(pathnames)$mtime
> print(ta)
[1] "2023-11-17 08:49:34 CET" "2023-11-17 08:49:34 CET"
[3] "2023-11-17 08:49:34 CET"
> 
> # Wait a bit...
> Sys.sleep(1.2)
> 
> # Touch zero files
> stopifnot(is.null(touchFile(NULL)))
> stopifnot(is.null(touchFile(character(0L))))
> 
> # Touch multiple files
> ta0 <- touchFile(pathnames)
> tb <- file.info(pathnames)$mtime
> print(tb)
[1] "2023-11-17 08:49:36 CET" "2023-11-17 08:49:36 CET"
[3] "2023-11-17 08:49:36 CET"
> 
> # Verify return value
> stopifnot(identical(ta0, ta))
> 
> # Verify that the timestamps got updated
> stopifnot(tb > ta)
> 
> # Touch a single file
> ta0 <- touchFile(pathnames[2L])
> tb <- file.info(pathnames[2L])$mtime
> print(tb)
[1] "2023-11-17 08:49:36 CET"
> 
> # Verify that the timestamps got updated
> stopifnot(tb > ta[2L])
> 
> # Verify that the content did not change
> md5b <- sapply(pathnames, FUN=digest::digest, file=TRUE)
> stopifnot(identical(md5a, md5b))
> 
> proc.time()
   user  system elapsed 
   0.26    0.14    1.60