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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |VERSIONS |STANDARDS |HISTORY |NOTES |SEE ALSO |COLOPHON | |
readdir(3) Library Functions Manualreaddir(3)readdir - read a directory
Standard C library (libc,-lc)
#include <dirent.h>struct dirent *readdir(DIR *dirp);
Thereaddir() function returns a pointer to adirent structure representing the next directory entry in the directory stream pointed to bydirp. It returns NULL on reaching the end of the directory stream or if an error occurred. In the glibc implementation, thedirent structure is defined as follows: struct dirent { ino_t d_ino; /* Inode number */ off_t d_off; /* Not an offset; see below */ unsigned short d_reclen; /* Length of this record */ unsigned char d_type; /* Type of file; not supported by all filesystem types */ char d_name[256]; /* Null-terminated filename */ }; The only fields in thedirent structure that are mandated by POSIX.1 ared_name andd_ino. The other fields are unstandardized, and not present on all systems; see VERSIONS. The fields of thedirent structure are as follows:d_ino This is the inode number of the file.d_off The value returned ind_off is the same as would be returned by callingtelldir(3) at the current position in the directory stream. Be aware that despite its type and name, thed_off field is seldom any kind of directory offset on modern filesystems. Applications should treat this field as an opaque value, making no assumptions about its contents; see alsotelldir(3).d_reclen This is the size (in bytes) of the returned record. This may not match the size of the structure definition shown above; see VERSIONS.d_type This field contains a value indicating the file type, making it possible to avoid the expense of callinglstat(2) if further actions depend on the type of the file. When a suitable feature test macro is defined (_DEFAULT_SOURCEsince glibc 2.19, or_BSD_SOURCEon glibc 2.19 and earlier), glibc defines the following macro constants for the value returned ind_type:DT_BLKThis is a block device.DT_CHRThis is a character device.DT_DIRThis is a directory.DT_FIFO This is a named pipe (FIFO).DT_LNKThis is a symbolic link.DT_REGThis is a regular file.DT_SOCK This is a UNIX domain socket.DT_UNKNOWN The file type could not be determined. Currently, only some filesystems (among them: Btrfs, ext2, ext3, and ext4) have full support for returning the file type ind_type. All applications must properly handle a return ofDT_UNKNOWN.d_name This field contains the null terminated filename; see VERSIONS. The data returned byreaddir() may be overwritten by subsequent calls toreaddir() for the same directory stream.On success,readdir() returns a pointer to adirent structure. (This structure may be statically allocated; do not attempt tofree(3) it.) If the end of the directory stream is reached, NULL is returned anderrno is not changed. If an error occurs, NULL is returned anderrno is set to indicate the error. To distinguish end of stream from an error, seterrno to zero before callingreaddir() and then check the value oferrno if NULL is returned.
EBADFInvalid directory stream descriptordirp.
For an explanation of the terms used in this section, seeattributes(7). ┌─────────────────────┬───────────────┬──────────────────────────┐ │Interface│Attribute│Value│ ├─────────────────────┼───────────────┼──────────────────────────┤ │readdir() │ Thread safety │ MT-Unsafe race:dirstream │ └─────────────────────┴───────────────┴──────────────────────────┘ In the current POSIX.1 specification (POSIX.1-2008),readdir() is not required to be thread-safe. However, in modern implementations (including the glibc implementation), concurrent calls toreaddir() that specify different directory streams are thread-safe. In cases where multiple threads must read from the same directory stream, usingreaddir() with external synchronization is still preferable to the use of the deprecatedreaddir_r(3) function. It is expected that a future version of POSIX.1 will require thatreaddir() be thread-safe when concurrently employed on different directory streams.
Only the fieldsd_name and (as an XSI extension)d_ino are specified in POSIX.1. Other than Linux, thed_type field is available mainly only on BSD systems. The remaining fields are available on many, but not all systems. Under glibc, programs can check for the availability of the fields not defined in POSIX.1 by testing whether the macros_DIRENT_HAVE_D_NAMLEN,_DIRENT_HAVE_D_RECLEN,_DIRENT_HAVE_D_OFF, or_DIRENT_HAVE_D_TYPE are defined.The d_name field Thedirent structure definition shown above is taken from the glibc headers, and shows thed_name field with a fixed size.Warning: applications should avoid any dependence on the size of thed_name field. POSIX defines it aschar d_name[], a character array of unspecified size, with at mostNAME_MAXcharacters preceding the terminating null byte ('\0'). POSIX.1 explicitly notes that this field should not be used as an lvalue. The standard also notes that the use ofsizeof(d_name) is incorrect; usestrlen(d_name) instead. (On some systems, this field is defined aschar d_name[1]!) By implication, the usesizeof(struct dirent) to capture the size of the record including the size ofd_name is also incorrect. Note that while the call fpathconf(fd, _PC_NAME_MAX) returns the value 255 for most filesystems, on some filesystems (e.g., CIFS, Windows SMB servers), the null-terminated filename that is (correctly) returned ind_name can actually exceed this size. In such cases, thed_reclen field will contain a value that exceeds the size of the glibcdirent structure shown above.POSIX.1-2008.
POSIX.1-2001, SVr4, 4.3BSD.
A directory stream is opened usingopendir(3). The order in which filenames are read by successive calls toreaddir() depends on the filesystem implementation; it is unlikely that the names will be sorted in any fashion.
getdents(2),read(2),closedir(3),dirfd(3),ftw(3),offsetof(3),opendir(3),readdir_r(3),rewinddir(3),scandir(3),seekdir(3),telldir(3)
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 2025-05-17readdir(3)Pages that refer to this page:sshfs(1), fanotify_mark(2), getdents(2), readdir(2), closedir(3), dirfd(3), fts(3), ftw(3), getdirentries(3), glob(3), opendir(3), readdir_r(3), rewinddir(3), scandir(3), seekdir(3), telldir(3), xfs_io(8)
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