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glibc  2.9
Functions
readlinkat.c File Reference
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysdep.h>
#include <unistd.h>
#include <kernel-features.h>

Go to the source code of this file.

Functions

ssize_t readlinkat (int fd, const char *path, char *buf, size_t len)

Function Documentation

ssize_t readlinkat ( int  fd,
const char *  path,
char *  buf,
size_t  len 
)

Definition at line 33 of file readlinkat.c.

{
  int result;

#ifdef __NR_readlinkat
# ifndef __ASSUME_ATFCTS
  if (__have_atfcts >= 0)
# endif
    {
      result = INLINE_SYSCALL (readlinkat, 4, fd, path, buf, len);
# ifndef __ASSUME_ATFCTS
      if (result == -1 && errno == ENOSYS)
       __have_atfcts = -1;
      else
# endif
       return result;
    }
#endif

#ifndef __ASSUME_ATFCTS
  char *pathbuf = NULL;

  if (fd != AT_FDCWD && path[0] != '/')
    {
      size_t pathlen = strlen (path);
      static const char procfd[] = "/proc/self/fd/%d/%s";
      /* Buffer for the path name we are going to use.  It consists of
        - the string /proc/self/fd/
        - the file descriptor number
        - the file name provided.
        The final NUL is included in the sizeof.   A bit of overhead
        due to the format elements compensates for possible negative
        numbers.  */
      size_t buflen = sizeof (procfd) + sizeof (int) * 3 + pathlen;
      pathbuf = __alloca (buflen);

      __snprintf (pathbuf, buflen, procfd, fd, path);
      path = pathbuf;
    }

  INTERNAL_SYSCALL_DECL (err);

  result = INTERNAL_SYSCALL (readlink, err, 3, path, buf, len);

  if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
    {
      __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, pathbuf);
      result = -1;
    }

  return result;
#endif
}

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