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https://github.com/QB64-Phoenix-Edition/QB64pe.git
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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
50 lines
2.5 KiB
Plaintext
50 lines
2.5 KiB
Plaintext
The '''INPUT''' file mode can only [[OPEN]] existing files with data in them for program [[INPUT (file statement)|INPUT]].
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{{PageSyntax}}
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:: OPEN filename$ FOR INPUT AS #filenumber%
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* If the filename does not exist, INPUT will create a program [[ERROR Codes|file error]]! Use [[_FILEEXISTS]] in QB64 to avoid errors.
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* The file number can be determined automatically by using a [[FREEFILE]] variable value.
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* Mode can use [[INPUT (file statement)|INPUT]] #, [[LINE INPUT (file statement)|LINE INPUT]] # or [[INPUT$]] to read the file data.
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* Use the [[EOF]] function to avoid reading data past the end of a file and creating an [[ERROR Codes|INPUT error]]!
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* Input file statements will use the same filenumber as the OPEN statement.
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* The INPUT mode allows the same file to be opened in another mode with a different number.
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''Example:'' Avoiding an INPUT mode or [[INPUT (file statement)|INPUT #]] read error using a FileExist function. QB64 can use the [[_FILEEXISTS]] function.
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{{CodeStart}} '' ''
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DIM Fdata$(100)
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INPUT "Enter data file name: ", datafile$
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IF FileExist%(datafile$) THEN
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D% = {{Cl|FREEFILE}}: count = 0
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{{Cl|OPEN}} datafile$ FOR {{Cl|INPUT (file mode)|INPUT}} AS #D%
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DO UNTIL {{Cl|EOF}}(D%)
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count = count + 1
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{{Cl|INPUT (file statement)|LINE INPUT}} #D%, Fdata$(count)
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IF count = 100 THEN {{Cl|EXIT}} DO ' don't exceed {{Cl|Arrays|array}} size!
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LOOP
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{{Cl|CLOSE}} #D%
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ELSE : PRINT "File not found!"
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END IF
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{{Cl|FUNCTION}} FileExist% (filename$)
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f% = {{Cl|FREEFILE}}
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{{Cl|OPEN}} filename$ FOR {{Cl|APPEND}} AS #f% ' check that file exists
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IF {{Cl|LOF}}(f%) THEN FileExist% = -1 {{Cl|ELSE}} {{Cl|CLOSE}} #f%: {{Cl|KILL}} filename$
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{{Cl|CLOSE}} #f%
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{{Cl|END FUNCTION}} '' ''
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{{CodeEnd}}
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: ''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.
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''See also:''
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* [[INPUT (file statement)|INPUT #]], [[LINE INPUT (file statement)|LINE INPUT #]], [[INPUT$]] {{text|(file input)}}
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* [[INPUT]], [[LINE INPUT]], [[INPUT$]] {{text|(keyboard input)}}
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* [[APPEND]], [[RANDOM]], [[OUTPUT]], [[BINARY]]
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* [[_FILEEXISTS]], [[_DIREXISTS]]
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{{PageNavigation}} |