R: Ascertain File Accessibility

file.access {base} | R Documentation

## Ascertain File Accessibility

### Description

Utility function to access information about files on the user's file systems.

### Usage

    file.access(names, mode = 0)

### Arguments

`names` | character vector containing file names. Tilde-expansion will be done: see `path.expand`.
`mode` | integer specifying access mode required: see ‘Details’.

### Details

The `mode` value can be the exclusive or of the following values

0

  test for existence.

1

  test for execute permission.

2

  test for write permission.

4

  test for read permission.

Permission will be computed for real user ID and real group ID (rather than the effective IDs).

Please note that it is not a good idea to use this function to test before trying to open a file. On a multi-tasking system, it is possible that the accessibility of a file will change between the time you call `file.access()` and the time you try to open the file. It is better to wrap file open attempts in `try`.

### Value

An integer vector with values `0` for success and `-1` for failure.

### Note

This is intended as a replacement for the S-PLUS function `access`, a wrapper for the C function of the same name, which explains the return value encoding. Note that the return value is false for success.

### See Also

`file.info` for more details on permissions, `Sys.chmod` to change permissions, and `try` for a ‘test it and see’ approach.

`file_test` for shell-style file tests.

### Examples

    fa <- file.access(dir("."))
    table(fa) # count successes & failures

[Package base version 3.1.2 Index]