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

Go to the source code of this file.

Functions

int linkat (int fromfd, const char *from, int tofd, const char *to, int flags)

Function Documentation

int linkat ( int  fromfd,
const char *  from,
int  tofd,
const char *  to,
int  flags 
)

Definition at line 31 of file linkat.c.

{
  int result;

#ifdef __NR_linkat
# ifndef __ASSUME_ATFCTS
  if (__have_atfcts >= 0)
# endif
    {
      result = INLINE_SYSCALL (linkat, 5, fromfd, from, tofd, to, flags);
# ifndef __ASSUME_ATFCTS
      if (result == -1 && errno == ENOSYS)
       __have_atfcts = -1;
      else
# endif
       return result;
    }
#endif

#ifndef __ASSUME_ATFCTS
  /* Without kernel support we cannot handle AT_SYMLINK_FOLLOW.  */
  if (flags != 0)
    {
      __set_errno (EINVAL);
      return -1;
    }

  static const char procfd[] = "/proc/self/fd/%d/%s";
  char *buffrom = NULL;

  if (fromfd != AT_FDCWD && from[0] != '/')
    {
      size_t filelen = strlen (from);
      /* 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 + filelen;
      buffrom = alloca (buflen);

      __snprintf (buffrom, buflen, procfd, fromfd, from);
      from = buffrom;
    }

  char *bufto = NULL;

  if (tofd != AT_FDCWD && to[0] != '/')
    {
      size_t filelen = strlen (to);
      /* 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 + filelen;
      bufto = alloca (buflen);

      __snprintf (bufto, buflen, procfd, tofd, to);
      to = bufto;
    }

  INTERNAL_SYSCALL_DECL (err);

  result = INTERNAL_SYSCALL (link, err, 2, from,  to);

  if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
    {
      __atfct_seterrno_2 (INTERNAL_SYSCALL_ERRNO (result, err), tofd, bufto,
                       fromfd, buffrom);
      result = -1;
    }

  return result;
#endif
}

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