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glibc  2.9
Functions
chown.c File Reference
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sysdep.h>
#include <stdlib.h>
#include <kernel-features.h>
#include <shlib-compat.h>

Go to the source code of this file.

Functions

int __chown (const char *file, uid_t owner, gid_t group)

Function Documentation

int __chown ( const char *  file,
uid_t  owner,
gid_t  group 
)

Definition at line 37 of file chown.c.

{
#if __ASSUME_LCHOWN_SYSCALL
  return INLINE_SYSCALL (chown, 3, file, owner, group);
#else
  int err;
  int old_errno;
  char link[PATH_MAX + 2];
  char path[2 * PATH_MAX + 4];
  int loopct;
  size_t filelen;
  static int libc_old_chown = 0 /* -1=old linux, 1=new linux, 0=unknown */;

  if (libc_old_chown == 1)
    return INLINE_SYSCALL (chown, 3, __ptrvalue (file), owner, group);

  old_errno = errno;

# ifdef __NR_lchown
  if (libc_old_chown == 0)
    {
      err = INLINE_SYSCALL (chown, 3, __ptrvalue (file), owner, group);
      if (err != -1 || errno != ENOSYS)
       {
         libc_old_chown = 1;
         return err;
       }
      libc_old_chown = -1;
    }
# endif

  err = __readlink (file, link, PATH_MAX + 1);
  if (err == -1)
    {
      __set_errno (old_errno);
      return __lchown (file, owner, group);
    }

  filelen = strlen (file) + 1;
  if (filelen > sizeof (path))
    {
      __set_errno (ENAMETOOLONG);
      return -1;
    }
  memcpy (path, file, filelen);

  /* 'The system has an arbitrary limit...'  In practise, we'll hit
     ENAMETOOLONG before this, usually.  */
  for (loopct = 0; loopct < 128; ++loopct)
    {
      size_t linklen;

      if (err >= PATH_MAX + 1)
       {
         __set_errno (ENAMETOOLONG);
         return -1;
       }

      link[err] = 0;  /* Null-terminate string, just-in-case.  */

      linklen = strlen (link) + 1;

      if (link[0] == '/')
       memcpy (path, link, linklen);
      else
       {
         filelen = strlen (path);

         while (filelen > 1 && path[filelen - 1] == '/')
           --filelen;
         while (filelen > 0 && path[filelen - 1] != '/')
           --filelen;
         if (filelen + linklen > sizeof (path))
           {
             errno = ENAMETOOLONG;
             return -1;
           }
         memcpy (path + filelen, link, linklen);
       }

      err = __readlink (path, link, PATH_MAX + 1);

      if (err == -1)
       {
         __set_errno (old_errno);
         return __lchown (path, owner, group);
       }
    }
  __set_errno (ELOOP);
  return -1;
#endif
}

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