filesystems

问题 I am wondering which Win32 API call is creating the files with UNICODE path. Just to make sure, I am not talking about the content here only the file path. I would appreciate if somebody would hit me with an MSDN url, my google fu failed this time. Thanks a million in advance. 回答1: See CreateFile msdn link: http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858%28v=vs.85%29.aspx, if you pass a unicode string to the lpFileName parameter then the unicode version of CreateFile will be

问题 this code: boost::filesystem::is_directory("/usr/include"); work fine. both this code: boost::filesystem::is_directory(L"/usr/include"); throw an exception: terminate called after throwing an instance of 'std::runtime_error' what(): locale::facet::_S_create_c_locale name not valid OS - Linux Mint boost-1.43 gcc-4.6.0 回答1: Don't use wide strings on Linux. You don't need them.. What happens that it tries to convert wide string to normal one and for this creates a locale and probably this locale

问题 I am creating an app in which I would like to make use of hardlinks and symlinks in the Android external memory filesystem. I have tried using the commands Os.link("oldpath", "newpath"); Os.link("oldpath", "newpath"); However, when I try this, I get this error: link failed: EPERM (Operation not permitted) This makes me think that you need root access, although I have seen other people do this same thing, and I would not think that they would have these commands if they needed root. Any ideas?

问题 This is an unresolved exam question of mine. Can two Unix processes simultaneous write to different positions in a single file? Yes, the two processes will have their own file table entries no, the shared i-node contains a single offset pointer only one process will have write privilege yes, but only if we operate using NFS 回答1: There is no file offset recorded in an inode so answer 2. is incorrect. There is no documented reason for a process to have its access rights modified so 3. is

问题 Since I have been told that if a user in my computer will create "infinite" number of folders / files (even empty) it can cause my computer to become much much slower (even stuck), I want to limit the maximum number of files/directories that user can create. I'm afraid that one user will try to create a huge number of files and it will become a problem for all the other users, so it will be a security issue, How do I do that, how do I limit the max number of files/directories each user can

问题 Apparently dbutils cannot be used in cmd-line spark-submits, you must use Jar Jobs for that, but I MUST use spark-submit style jobs due to other requirements, yet still have a need to list and iterate over file keys in dbfs to make some decisions about which files to use as input to a process... Using scala, what lib in spark or hadoop can I use to retrieve a list of dbfs:/filekeys of a particular pattern? import org.apache.hadoop.fs.Path import org.apache.spark.sql.SparkSession def ls

问题 Apparently dbutils cannot be used in cmd-line spark-submits, you must use Jar Jobs for that, but I MUST use spark-submit style jobs due to other requirements, yet still have a need to list and iterate over file keys in dbfs to make some decisions about which files to use as input to a process... Using scala, what lib in spark or hadoop can I use to retrieve a list of dbfs:/filekeys of a particular pattern? import org.apache.hadoop.fs.Path import org.apache.spark.sql.SparkSession def ls

问题 Assume we have a file of FILE_SIZE bytes, and: FILE_SIZE <= min(page_size, physical_block_size) ; file size never changes (i.e. truncate() or append write() are never performed); file is modified only by completly overwriting its contents using: pwrite(fd, buf, FILE_SIZE, 0); Is it guaranteed on ext4 that: Such writes are atomic with respect to concurrent reads? Such writes are transactional with respect to a system crash? (i.e., after a crash the file's contents is completely from some

问题 Assume we have a file of FILE_SIZE bytes, and: FILE_SIZE <= min(page_size, physical_block_size) ; file size never changes (i.e. truncate() or append write() are never performed); file is modified only by completly overwriting its contents using: pwrite(fd, buf, FILE_SIZE, 0); Is it guaranteed on ext4 that: Such writes are atomic with respect to concurrent reads? Such writes are transactional with respect to a system crash? (i.e., after a crash the file's contents is completely from some

问题 Assume we have a file of FILE_SIZE bytes, and: FILE_SIZE <= min(page_size, physical_block_size) ; file size never changes (i.e. truncate() or append write() are never performed); file is modified only by completly overwriting its contents using: pwrite(fd, buf, FILE_SIZE, 0); Is it guaranteed on ext4 that: Such writes are atomic with respect to concurrent reads? Such writes are transactional with respect to a system crash? (i.e., after a crash the file's contents is completely from some