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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |STANDARDS |HISTORY |EXAMPLES |SEE ALSO |COLOPHON | |
VFAT_IOCTL_READDIR_BOTH(2const)VFAT_IOCTL_READDIR_BOTH(2const)VFAT_IOCTL_READDIR_BOTH, VFAT_IOCTL_READDIR_SHORT - read filenames of a directory in a FAT filesystem
Standard C library (libc,-lc)
#include <linux/msdos_fs.h>/* Definition ofVFAT_*constants */#include <sys/ioctl.h>int ioctl(intfd, VFAT_IOCTL_READDIR_BOTH,struct __fat_dirententry[2]);int ioctl(intfd, VFAT_IOCTL_READDIR_SHORT,struct __fat_dirententry[2]);
A file or directory on a FAT filesystem always has a short filename consisting of up to 8 capital letters, optionally followed by a period and up to 3 capital letters for the file extension. If the actual filename does not fit into this scheme, it is stored as a long filename of up to 255 UTF-16 characters. The short filenames in a directory can be read withVFAT_IOCTL_READDIR_SHORT.VFAT_IOCTL_READDIR_BOTHreads both the short and the long filenames. Thefd argument must be a file descriptor for a directory. It is sufficient to create the file descriptor by callingopen(2) with theO_RDONLYflag. The file descriptor can be used only once to iterate over the directory entries by callingioctl(2) repeatedly. Theentry argument is a two-element array of the following structures: struct __fat_dirent { long d_ino; __kernel_off_t d_off; uint32_t short d_reclen; char d_name[256]; }; The first entry in the array is for the short filename. The second entry is for the long filename. Thed_ino andd_off fields are filled only for long filenames. Thed_ino field holds the inode number of the directory. Thed_off field holds the offset of the file entry in the directory. As these values are not available for short filenames, the user code should simply ignore them. The fieldd_reclen contains the length of the filename in the fieldd_name. To keep backward compatibility, a length of 0 for the short filename signals that the end of the directory has been reached. However, the preferred method for detecting the end of the directory is to test theioctl(2) return value. If no long filename exists, fieldd_reclen is set to 0 andd_name is a character string of length 0 for the long filename.A return value of 1 signals that a new directory entry has been read and a return value of 0 signals that the end of the directory has been reached. On error, -1 is returned, anderrno is set to indicate the error.
ENOENTfd refers to a removed, but still open directory.ENOTDIRfd does not refer to a directory.
Linux.
Linux 2.0.
The following program demonstrates the use ofioctl(2) to list a directory. The following was recorded when applying the program to the directory/mnt/user: $./fat_dir /mnt/user; . -> '' .. -> '' ALONGF~1.TXT -> 'a long filename.txt' UPPER.TXT -> '' LOWER.TXT -> 'lower.txt'Program source #include <fcntl.h> #include <linux/msdos_fs.h> #include <stdio.h> #include <stdlib.h> #include <sys/ioctl.h> #include <unistd.h> int main(int argc, char *argv[]) { int fd; int ret; struct __fat_dirent entry[2]; if (argc != 2) { printf("Usage: %s DIRECTORY\n", argv[0]); exit(EXIT_FAILURE); } /* * Open file descriptor for the directory. */ fd = open(argv[1], O_RDONLY | O_DIRECTORY); if (fd == -1) { perror("open"); exit(EXIT_FAILURE); } for (;;) { /* * Read next directory entry. */ ret = ioctl(fd, VFAT_IOCTL_READDIR_BOTH, entry); /* * If an error occurs, the return value is -1. * If the end of the directory list has been reached, * the return value is 0. * For backward compatibility the end of the directory * list is also signaled by d_reclen == 0. */ if (ret < 1) break; /* * Write both the short name and the long name. */ printf("%s -> '%s'\n", entry[0].d_name, entry[1].d_name); } if (ret == -1) { perror("VFAT_IOCTL_READDIR_BOTH"); exit(EXIT_FAILURE); } /* * Close the file descriptor. */ close(fd); exit(EXIT_SUCCESS); }ioctl(2),ioctl_fat(2)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17VFAT_IOCTL_READDIR_BOTH(2const)Pages that refer to this page:ioctl_fat(2)
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