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 a file
> pathname <- "foobar.txt"
> cat(file=pathname, "File v1\n")
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # (a) Backup and restore a file
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Turn it into a backup file
> pathnameB <- pushBackupFile(pathname, verbose=TRUE)
Adding backup suffix from file...
 Pathname: foobar.txt
 Suffix: .bak
 Rename existing file?: TRUE
 Backup pathname: foobar.txt.bak
 Renaming existing file...
  Result: TRUE
 Renaming existing file...done
Adding backup suffix from file...done
> print(pathnameB)
[1] "foobar.txt.bak"
> 
> # Restore main file from backup
> pathnameR <- popBackupFile(pathnameB, verbose=TRUE)
Dropping backup suffix from file...
 Backup pathname: foobar.txt.bak
 Suffix: .bak
 Regular expression for suffix: \.bak$
 Pathname: foobar.txt
 Renaming existing backup file...
  Result: TRUE
 Renaming existing backup file...done
Dropping backup suffix from file...done
> print(pathnameR)
[1] "foobar.txt"
> 
> 
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # (b) Backup, create a new file and frop backup file
> # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> # Turn it into a backup file
> pathnameB <- pushBackupFile(pathname, verbose=TRUE)
Adding backup suffix from file...
 Pathname: foobar.txt
 Suffix: .bak
 Rename existing file?: TRUE
 Backup pathname: foobar.txt.bak
 Renaming existing file...
  Result: TRUE
 Renaming existing file...done
Adding backup suffix from file...done
> print(pathnameB)
[1] "foobar.txt.bak"
> 
> # Create a new file
> cat(file=pathname, "File v2\n")
> 
> # Drop backup because a new main file was successfully created
> pathnameR <- popBackupFile(pathnameB, verbose=TRUE)
Dropping backup suffix from file...
 Backup pathname: foobar.txt.bak
 Suffix: .bak
 Regular expression for suffix: \.bak$
 Pathname: foobar.txt
 Dropping backup file because target file already exists...
  Result: TRUE
 Dropping backup file because target file already exists...done
Dropping backup suffix from file...done
> print(pathnameR)
[1] "foobar.txt"
> 
> file.remove(pathname)
[1] TRUE
> 
> proc.time()
   user  system elapsed 
    0.4     0.1     0.5