Visualizza wikitesto di Conoscere caratteristiche generali dei file

Per ottenere informazioni di tipo generale sui file, è possibile operare con risorse di Gambas o del linguaggio C.


==Uso della Classe ''Stat()'' di Gambas==
Per l'uso della risorsa ''Stat()'' di Gambas rimandiamo a [[stat|questa pagina della Wiki]].



==Uso della funzione ''stat()'' di C==
La funzione ''stat()'' di C potrà essere richiamata in modo <SPAN Style="text-decoration:underline">diretto</span> come funzione esterna mediante ''Extern'', come descritto nella [[Stat_()|seguente pagina della Wiki]], oppure in modo <SPAN Style="text-decoration:underline">indiretto</span> utilizzandola all'interno di una libreria esterna condivisa da noi creata ''ad hoc''.

Per il secondo caso mostriamo un esempio pratico:
 Public Struct STATUS_File
   st_dev As Long
   st_ino As Long
   st_nlink As Long
   st_mode As Integer
   st_uid As Integer
   st_gid As Long
   st_rdev As Long
   st_size As Long
   st_blksize As Long
   st_blocks As Long
   st_atime As Long
   unused1 As Integer
   st_mtime As Long
   unused2 As Long
   st_ctime As Long
   __glibc_reserved[3] As Long
 End Struct
 
  
 Library "libc:6"
 
 <FONT Color=gray>' ''tm* localtime( const time_t *time )''
 ' ''Converts given time since epoch as time_t value into calendar time, expressed in local time.''</font>
 Private Extern localtime(tm As Pointer) As Pointer
 
 <FONT Color=gray>' ''char* asctime( const tm* time_ptr )''
 ' ''Converts given calendar time tm to a textual representation.''</font>
 Private Extern asctime(time_ptr As Pointer) As String
 
 <FONT Color=gray>' ''int Chiama_stat(const char *s, struct stat *st)''
 ' ''Invoca la funzione stat() dichiarata nel file header stat.h.''</font>
 Private Extern Chiama_stat(nomefile As String, stFile As STATUS_File) As Integer In "/tmp/libSTATUS"
 
 
 '''Public''' Sub Main()
 
  Dim i As Integer
  Dim stS As New STATUS_File
  Dim at, mt, ct As Long
  Dim s As String
  
 <FONT Color=gray>' ''Chiama la procedura per creare la libreria esterna ad hoc:''</font>
  Creaso()
  
  s = "<FONT Color=gray>''/percorso/del/file''</font>"
  
  i = Chiama_stat(s, stS)
  If i <> 0 Then Error.Raise("Errore nella chiamata della funzione 'Chiama_stat()' !")
  
  Print "File controllato: "; s
  Print
   
  With stS
    Print .st_dev
    Print .st_ino
    Print .st_nlink
    Print .st_mode
    Print .st_uid
    Print .st_gid
    Print .st_rdev
    Print .st_size; " byte"
    Print .st_blksize
    Print .st_blocks
    at = .st_atime
    mt = .st_mtime
    ct = .st_ctime
  End With
  
  Print Trim(asctime(localtime(VarPtr(at))))
  Write asctime(localtime(VarPtr(mt)))
  Write asctime(localtime(VarPtr(ct)))
   
 '''End'''
  
  
 '''Private''' Procedure Creaso()
  
  File.Save("/tmp/libSTATUS.c", "#include <sys/stat.h>\n\n" &
                                "struct stat status;\n\n" &
                                "int Chiama_stat(const char *s, struct stat *st) {\n" &
                                "   int r;\n" &
                                "   r = stat(s, &status);\n" &
                                "   *st = status;\n" &
                                "   return r;\n}")
  
 <FONT Color=gray>' ''Genera la libreria esterna ad hoc:''</font>
  Shell "gcc -o /tmp/libSTATUS.so /tmp/libSTATUS.c -shared -fPIC" Wait
   
 '''End'''


==Uso della funzione ''g_stat()'' della libreria ''Glib''==
Si potrà utilizzare anche la funzione ''g_stat()'' della libreria "''libglib-2.0.so''", la quale passerà ''per riferimento'' una Struttura identica a quella già vista sopra e definita nel file ''/bits/stat.h''.


Il codice Gambas sarà:
 Public Struct STATUS_File
   st_dev As Long
   st_ino As Long
   st_nlink As Long
   st_mode As Integer
   st_uid As Integer
   st_gid As Long
   st_rdev As Long
   st_size As Long
   st_blksize As Long
   st_blocks As Long
   st_atime As Long
   unused1 As Integer
   st_mtime As Long
   unused2 As Long
   st_ctime As Long
   __glibc_reserved[3] As Long
 End Struct
 
 
 <FONT Color=gray>' ''int g_stat (const gchar *filename, GStatBuf *buf)''
 ' ''Returns information about a file.''</font>
 Private Extern g_stat(filename As String, buf As STATUS_File) As Integer In "libglib-2.0"
  
 
 Library "libc:6"
 
 <FONT Color=gray>' ''tm* localtime( const time_t *time )''
 ' ''Converts given time since epoch as time_t value into calendar time, expressed in local time.''</font>
 Private Extern localtime(tm As Pointer) As Pointer
 
 <FONT Color=gray>' ''char* asctime( const tm* time_ptr )''
 ' ''Converts given calendar time tm to a textual representation.''</font>
 Private Extern asctime(time_ptr As Pointer) As String
 
 
 '''Public''' Sub Main()
 
  Dim sta As New STATUS_File
  Dim at, mt, ct As Long
 
   <FONT Color=#B222222>g_stat("''/percorso/del/file/''", sta)</font>
    
   With sta
     Print .st_dev
     Print .st_ino
     Print .st_nlink
     Print .st_mode
     Print .st_uid
     Print .st_gid
     Print .st_rdev
     Print .st_size; " byte"
     Print .st_blksize
     Print .st_blocks
     at = .st_atime
     mt = .st_mtime
     ct = .st_ctime
   End With
  
   Print asctime(localtime(VarPtr(at)))
   Print asctime(localtime(VarPtr(mt)))
   Print asctime(localtime(VarPtr(ct)))
 
 '''End'''