QB64-PE/internal/help/INPUT_(file_mode).txt

The '''INPUT''' file mode can only [[OPEN]] existing files with data in them for program [[INPUT (file statement)|INPUT]].


{{PageSyntax}}
:: OPEN filename$ FOR INPUT AS #filenumber%


* If the filename does not exist, INPUT will create a program [[ERROR Codes|file error]]! Use [[_FILEEXISTS]] in QB64 to avoid errors.
* The file number can be determined automatically by using a [[FREEFILE]] variable value.
* Mode can use [[INPUT (file statement)|INPUT]] #, [[LINE INPUT (file statement)|LINE INPUT]] # or [[INPUT$]] to read the file data.
* Use the [[EOF]] function to avoid reading data past the end of a file and creating an [[ERROR Codes|INPUT error]]!
* Input file statements will use the same filenumber as the OPEN statement.
* The INPUT mode allows the same file to be opened in another mode with a different number.


''Example:'' Avoiding an INPUT mode or [[INPUT (file statement)|INPUT #]] read error using a FileExist function. QB64 can use the [[_FILEEXISTS]] function.

{{CodeStart}} '' ''
 DIM Fdata$(100)
 INPUT "Enter data file name: ", datafile$ 
 IF FileExist%(datafile$) THEN
    D% = {{Cl|FREEFILE}}: count = 0
    {{Cl|OPEN}} datafile$ FOR {{Cl|INPUT (file mode)|INPUT}} AS #D%
    DO UNTIL {{Cl|EOF}}(D%)
     count = count + 1
     {{Cl|INPUT (file statement)|LINE INPUT}} #D%, Fdata$(count)
     IF count = 100 THEN {{Cl|EXIT}} DO  ' don't exceed {{Cl|Arrays|array}} size!
    LOOP
  {{Cl|CLOSE}} #D%
 ELSE : PRINT "File not found!"
 END IF

 {{Cl|FUNCTION}} FileExist% (filename$)
   f% = {{Cl|FREEFILE}}  
   {{Cl|OPEN}} filename$ FOR {{Cl|APPEND}} AS #f% ' check that file exists
   IF {{Cl|LOF}}(f%) THEN FileExist% = -1 {{Cl|ELSE}} {{Cl|CLOSE}} #f%: {{Cl|KILL}} filename$
   {{Cl|CLOSE}} #f%
 {{Cl|END FUNCTION}} '' ''
{{CodeEnd}}
: ''Explanation:'' The function opens the filename in [[APPEND]] mode to see if there is data in the file. It also creates the file if it did not exist. [[LOF]] will return 0 if the file is empty and cannot be read. In fact you can [[KILL]] the file if it is empty. If it is not empty then the function returns -1 and the existing file can be opened for INPUT and read by the program. [[_FILEEXISTS]] doesn't create any files.


''See also:'' 
* [[INPUT (file statement)|INPUT #]], [[LINE INPUT (file statement)|LINE INPUT #]], [[INPUT$]] {{text|(file input)}}
* [[INPUT]], [[LINE INPUT]], [[INPUT$]] {{text|(keyboard input)}}
* [[APPEND]], [[RANDOM]], [[OUTPUT]], [[BINARY]]
* [[_FILEEXISTS]], [[_DIREXISTS]]


{{PageNavigation}}