Syntax

  #include <unistd.h>  
   
  LONG lseek  (  
     int    handle,   
     LONG   offset,   
     int    origin);
  

Parameters

handle

(IN) Specifies a file handle.

offset

(IN) Specifies the relative offset from a file position.

origin

(IN) Specifies the seek starting point.

Return Values

On success, lseek returns the new current file position in a system-dependent manner. A value of 0 indicates the start of a file. If an error occurs, lseek returns 0xFFFFFFFF, and errno is set to:.

If lseek does not complete successfully, NetWareErrno is also set.

Remarks

The file is referenced using the specified file handle.

The value of the offset parameter is used as a relative offset from a file position determined by the value of the origin parameter. An absolute offset can be from 0 to 2 ³². It must be unsigned long, which cannot be negative.

The new file position is determined in a manner dependent upon the value of the origin parameter, which can have one of three possible values (defined in the STDIO.H header file):

The files’s position can be set to a position outside of the bounds of the file.

See Also

close, creat, dup, dup2, eof, filelength, fileno, fstat, isatty, open, read, sopen, tell, write

Example

  #include <stddef.h>  
  #include <stdio.h>  
  #include <stdlib.h>  
  #include <unistd.h>  
  #include <fcntl.h>  
  #include <errno.h>  
   
  main()  
  {  
     int   fh;  
     if((fh = open ("test.dat",O_RDWR | O_CREAT | O_TRUNC,0)) < 0)  
     {  
        printf ("could not open file\r\n");  
        exit(0);  
     }  
     write (fh,"1234567890",10);  
     if(lseek (fh,1,SEEK_SET) < 0)  
     {  
        printf ("error on seek 1\r\n");  
        goto end;  
     }  
     write (fh,"a",1);  
     if(lseek(fh,-2,SEEK_END) < 0)  
     {  
        printf ("error on seek 2\r\n");  
        goto end;  
     }  
     write (fh,"b",1);  
     if(lseek (fh,-5,SEEK_CUR) < 0)  
     {  
        printf ("error on seek 3\r\n");  
        goto end;  
     }  
     write (fh,"c",1);  
     end:  
     close (fh);  
     getch ();  
  }