fstat

obtain information about an open file

Synopsis:

#include <sys/types.h>
#include <sys/stat.h>
int  fstat( int filedes, struct stat *buf );

Description:

The fstat() function obtains information about an open file whose file descriptor is filedes. This information is placed in the structure located at the address indicated by buf.

The file sys/stat.h contains definitions for the structure stat.

At least the following macros are defined in the sys/stat.h header file:

S_ISBLK(m)

Test for block special file.

S_ISCHR(m)

Test for character special file.

S_ISDIR(m)

Test for directory file.

S_ISFIFO(m)

Test for FIFO.

S_ISLNK(m)

Test for symbolic link.

S_ISREG(m)

Test for regular file.

The value m supplied to the macros is the value of the st_mode field of a stat structure. The macro evaluates to a non-zero value if the test is true, and zero if the test is false.

The access permissions for the file or directory are specified as a combination of bits in the st_mode field of a stat structure. These bits are defined in the sys/stat.h header file, and are described in the section on this file in “Header Files in /usr/include/sys” of the C Library Overview chapter. The following bits are also encoded in the st_mode field:

S_ISUID

Set user ID on execution. The process's effective user ID is set to that of the owner of the file when the file is run as a program. On a regular file, this bit should be cleared on any write.

S_ISGID

Set group ID on execution. Set effective group ID on the process to the file's group when the file is run as a program. On a regular file, this bit should be cleared on any write.

Returns:

0

the information was successfully obtained.

non-zero

the information wasn't successfully obtained. When an error has occurred, errno contains a value indicating the type of error that has been detected.

Errors:

EBADF

The filedes argument is not a valid file descriptor .

See also:

creat(), dup(), dup2(), errno, fcntl(), fsys_stat(), fsys_fstat(), lstat(), open(), sopen(), stat(), pipe()

Examples:

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

void main()
  {
    int filedes, rc;
    struct stat buf;

    filedes = open( "file", O_RDONLY );
    if( filedes != -1 ) {
      rc = fstat( filedes , &buf );
      if( rc != -1 )
        printf( "File size = %d\n", buf.st_size );
      close( filedes );
    }
  }

Classification:

Systems: