Extract File Information

Description

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

Usage

file.info(..., extra_cols = TRUE)

file.mode(...)
file.mtime(...)
file.size(...)

Arguments

Details

What constitutes a ‘file’ is OS-dependent but includes directories. (However, directory names must not include a trailing backslash or slash on Windows.) See also the section in the help for file.exists on case-insensitive file systems.

The file ‘mode’ follows POSIX conventions, giving three octal digits summarizing the permissions for the file owner, the owner's group and for anyone respectively. Each digit is the logical or of read (4), write (2) and execute/search (1) permissions.

See files for how file paths with marked encodings are interpreted.

On unix alikes:

On most systems symbolic links are followed, so information is given about the file to which the link points rather than about the link.

On Windows:

File modes are probably only useful on NTFS file systems, and it seems all three digits refer to the file's owner. The execute/search bits are set for directories, and for files based on their extensions (e.g., ‘.exe’, ‘.com’, ‘.cmd’ and ‘.bat’ files). file.access will give a more reliable view of read/write access availability to the R process.

UTF-8-encoded file names not valid in the current locale can be used.

Junction points and symbolic links are followed, so information is given about the file/directory to which the link points rather than about the link.

Value

For file.info(), data frame with row names the file names and columns

On unix alikes:

uid:

integer, the user ID of the file's owner.

gid:

integer, the group ID of the file's group.

uname:

character, uid interpreted as a user name.

grname:

character, gid interpreted as a group name.

Unknown user and group names will be NA.

On Windows only:

exe:

character indicating the sort of executable. Possible values are "no", "msdos", "win16", "win32", "win64" and "unknown". Note that a file (e.g., a script file) can be executable according to the mode bits but not executable in this sense.

If extra_cols is false, only the first six columns are returned: as these can all be found from a single C system call this can be faster. (However, properly configured systems will use a ‘name service cache daemon’ to speed up the name lookups.)

Entries for non-existent or non-readable files will be NA.

The uid, gid, uname and grname columns may not be supplied on a non-POSIX Unix-alike system, and will not be on Windows.

What is meant by the three file times depends on the OS and file system. On Windows native file systems ctime is the file creation time (something which is not recorded on most Unix-alike file systems). What is meant by ‘file access’ and hence the ‘last access time’ is system-dependent.

The resolution of the file times depends on both the OS and the type of the file system. Modern file systems typically record times to an accuracy of a microsecond or better: notable exceptions are HFS+ on macOS (recorded in seconds) and modification time on older FAT systems (recorded in increments of 2 seconds). Note that "POSIXct" times are by default printed in whole seconds: to change that see strftime.

file.mode(), file.mtime() and file.size() are fast convenience wrappers returning just one of the columns.

Note

Some (now old) unix alike systems allow files of more than 2Gb to be created but not accessed by the stat system call. Such files may show up as non-readable (and very likely not be readable by any of R's input functions).

See Also

Sys.readlink to find out about symbolic links, files, file.access, list.files, and DateTimeClasses for the date formats.

Sys.chmod to change permissions.

Examples

ncol(finf <- file.info(dir()))  # at least six
finf # the whole list
## Those that are more than 100 days old :
finf <- file.info(dir(), extra_cols = FALSE)
finf[difftime(Sys.time(), finf[,"mtime"], units = "days") > 100 , 1:4]

file.info("no-such-file-exists")

## E.g., for R-core, in a R-devel version:
if(Sys.info()[["sysname"]] == "Linux") 
    sort(file.mtime(file.path(R.home("bin"),
                             c("",
                               file.path(c("", "exec"), "R")))
         ))