Copy copies a file and writes/overwrites to the destination file.

CopyAppend copies a file and appends to the destination file.

EnsureExecutable sets the executable file mode bits, for all users, to ensure that we can execute a file.

Exist returns true if a file or directory exists.

GetTempFilePath creates a file path to a temporary file that does not exist yet.

IsDirWriteable checks if dir is writable by writing and removing a file.

MkTmpDir creates a temp directory.

WriteTempFile writes data to a temporary file.

WriteToTempDir writes data to a temporary directory.