R: Help writing a general function to prevent overwriting files when saving objects

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I'm trying to gain some control over when graphic objects are being saved and stumbled across this related post from 8+ years ago: https://stackoverflow.com/a/1541872/5322644 I'd like to come up with a more general approach and below is my current attempt. Of course, it doesn't work and so I'd appreciate some help on it.

 ## safely avoid overwriting files when saving objects using a user specified save.function 

safeSave <- function(save.function = save, ..., file=stop("'file' must be specified"), overwrite=FALSE ) {
  if ( file.exists(file) & !overwrite ) stop("'file' already exists")
  do.call(save.function, as.list( ..., file = file))
}
    
## Try using function.
## It appears to be trying to save the value of `tmp` rather than the variable `tmp`
tmp = 10
safeSave(save, tmp, file = "tmp.Rda") 
# Error in (function (..., list = character(), file = stop("'file' must be specified"),  : object ‘10’ not found
r save function
1 Answers

Here's what I learned: when using save(), use the name of your object as a string. I also changed as.list() to list(), but I'm not sure why this made a difference.

Your function with slight modifications:

safeSave <- function(save.function = save, ..., file=stop("'file' must be specified"), overwrite=FALSE ) {
  if ( file.exists(file) & !overwrite ) stop("'file' already exists")
  do.call(save.function, list(..., file = file))
}

I had some issues getting save() to work, so I tried saveRDS():

## Test with saveRDS()

tmp <- 10
file = "tmp.rds"
safeSave(saveRDS, tmp, file = file) 

# Check if file exists
file.exists(file)
#> [1] TRUE
# Correct contents
a <- readRDS(file)
a
#> [1] 10

# Attempt to overwrite
safeSave(save, "tmp", file = file)
#> Error in safeSave(save, "tmp", file = file): 'file' already exists

That worked fine.

Now save(). Note that I'm using "tmp" instead of tmp:

## Test with save()

file <- "tmp.rda"
tmp <- 10
safeSave(save, "tmp", file = file)

# Clean envir then load from file
rm(list=ls())
file <- "tmp.rda"
load(file)
tmp
#> [1] 10
user_100218760
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