readdir(2) System Calls Manual readdir(2)

readdir - read directory entry

Standard C library (libc, -lc)

#include <sys/syscall.h>      /* Definition of SYS_* constants */
#include <unistd.h>
int syscall(SYS_readdir, unsigned int fd,
            struct old_linux_dirent *dirp, unsigned int count);

Note: There is no definition of struct old_linux_dirent; see NOTES.

This is not the function you are interested in. Look at readdir(3) for the POSIX conforming C library interface. This page documents the bare kernel system call interface, which is superseded by getdents(2).

readdir() reads one old_linux_dirent structure from the directory referred to by the file descriptor fd into the buffer pointed to by dirp. The argument count is ignored; at most one old_linux_dirent structure is read.

The old_linux_dirent structure is declared (privately in Linux kernel file fs/readdir.c) as follows:


struct old_linux_dirent {
    unsigned long d_ino;     /* inode number */
    unsigned long d_offset;  /* offset to this old_linux_dirent */
    unsigned short d_namlen; /* length of this d_name */
    char  d_name[1];         /* filename (null-terminated) */
}

d_ino is an inode number. d_offset is the distance from the start of the directory to this old_linux_dirent. d_reclen is the size of d_name, not counting the terminating null byte ('\0'). d_name is a null-terminated filename.

On success, 1 is returned. On end of directory, 0 is returned. On error, -1 is returned, and errno is set to indicate the error.

Invalid file descriptor fd.
Argument points outside the calling process's address space.
Result buffer is too small.
No such directory.
File descriptor does not refer to a directory.

You will need to define the old_linux_dirent structure yourself. However, probably you should use readdir(3) instead.

This system call does not exist on x86-64.

Linux.

getdents(2), readdir(3)

2024-06-15 Linux man-pages 6.9.1