FILE_Open
|
<< Click to Display Table of Contents >> Navigation: ThinBASIC Modules > File > FILE: functions working on files > FILE_Open |
Description
Prepare a file or device for reading or writing.
Syntax
n = FILE_OPEN(FileName, Mode, [RecordSize])
Returns
Number.
0 means errors.
> 0 means file number
Parameters
Name |
Type |
Optional |
Meaning |
||||||||||||||||||
FileName |
String |
No |
Name of the file to be opened |
||||||||||||||||||
Mode |
String |
No |
Specifies the file organization and style of access (sequential, random access, or binary) for reading, writing (or both), or appending. Posible values:
|
||||||||||||||||||
RecordSize |
Number |
Yes |
Len of the record or internal file buffer |
Remarks
Restrictions
Attempting to open a file for "INPUT" that does not exist causes an Error 53 ("File not found").
Attempting to open a file that is locked can result in either an Error 70 ("Permission denied"), or an Error 75 ("Path/file access error").Similarly, attempting to OPEN a file using a file number that is already in use will result in a run-time Error 55 ("File is already open "). For this reason, programs that use hard-coded file numbers should take special care to close files before the file number is used again. In addition, code that may be used by more than one thread should use FREEFILE and avoid hard-coded file numbers.
If you try to open a nonexistent file for OUTPUT, APPEND, RANDOM, or BINARY operations, a new file is automatically created.
See also
Examples
Thanks to Abraxas for the following script example
USES "FILE"
Dim FileHandle As DWORD
Dim Status As DWORD
Dim TestString As String
Dim FileName As String
Dim sMsg As String
TestString = "1234567890ABCDEF" ' String to write to file
FileName = APP_SCRIPTPATH + "test.txt" ' Build filename
'
' Here are two methods of saving the test string to a file
'
' First method
'
' Limitations - it will only write what is in the SringBuffer
' Advantages - Handles opening/closing the file
'
Status = FILE_SAVE(FileName, TestString) ' Save string to File
'
' Second method
'
' Limitations - None (that i can think of)
' Advantages - You can add and remove data
'
' The seek function can be used to move around the file to set the read / write position
'
FileHandle = FILE_Open (FileName, "BINARY") ' Open file for writing
Status = FILE_PUT (FileHandle, TestString) ' Write String to File
Status = FILE_Seek (FileHandle, 5) ' Set the current write position to 5th byte in the file
Status = FILE_PUT (FileHandle, TestString) ' Write String to File
Status = FILE_Close(FileHandle) ' Release File
'
' Now lets try and read some bytes back into memory
' Lets build the string '166'
'
sMsg = "Bytes read from file are " + $DQ
FileHandle = FILE_Open(FileName, "BINARY") ' Open file for reading
Status = FILE_Seek(FileHandle, 1) ' Set the current read position to 1st byte in the file
sMsg += FILE_Get (FileHandle, 1) ' Read 1 byte and add to output message
Status = FILE_Seek(FileHandle, 10) ' Reset the current File read position to 10th byte in the file
sMsg += FILE_Get (FileHandle, 1) ' Read 1 byte and add to output message
Status = FILE_Seek(FileHandle, 10) ' File read position has moved to the next byte so we need to Reset to 10th byte in the file
sMsg += FILE_Get (FileHandle, 1) ' Read 1 byte and add to output message
Status = FILE_Close(FileHandle) ' Release File
sMsg += $DQ + $CRLF + $CRLF
sMsg += "File Contents " + $DQ
sMsg += FILE_LOAD(FileName) ' Read File into Ouput string buffer
sMsg += $DQ
MSGBOX 0, sMsg ' Output string buffer