OpenFile
int OpenFile (char fileName[], int readWriteMode, int action, int fileType);
Purpose
Opens a file for reading or writing and returns a file handle for use in subsequent file operations.
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Note Remember to call CloseFile when you are finished with operations on the file. |
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Caution The Windows SDK also contains a function with the same name. Include windows.h before including formatio.h to ensure that there are no compilation errors as a result of this naming conflict. Define the SDK_CONFLICT_PRIORITYSDK_CONFLICT_PRIORITY macro to force LabWindows/CVI to use the Windows SDK implementation of this function. |
Parameters
| Input | ||||
| Name | Type | Description | ||
| fileName | char [] | Pathname that specifies the file to open. | ||
| readWriteMode | int | Specifies what combination of reading and writing you may perform on the file. If the read/writeMode argument is write or read/write, OpenFile creates the file if it does not already exist. Use GetFileInfo to determine whether a file already exists. OpenFile creates files with full read and write permissions.
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| action | int | Specifies whether to delete the old contents of the file and whether to force
the file pointer to the end of the file before each write operation. action is meaningful only if read/writeMode is VAL_READ_WRITE or VAL_WRITE_ONLY. After you perform read operations, the file pointer points to the byte that follows the last byte read. action values are as follows:
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| fileType | int | Specifies whether to treat the data in the file as ASCII or binary. When you perform I/O
on a file in binary mode, carriage returns (CR) and linefeeds (LF) receive no special treatment. When you open the file in ASCII mode, each CR/LF combination translates to an LF when reading, and each LF translates to a CR/LF combination when writing. fileType values are as follows:
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Return Value
| Name | Type | Description |
| fileHandle | int | File handle to be used in subsequent ReadFile/WriteFile calls. If this value is –1, an error occurred. The function failed, was unable to open the file, or a bad argument was passed to the function. You can use GetFmtIOError to get more information about the type of error that occurred. |
Additional Information
Library: Formatting and I/O Library
Include file: formatio.h
LabWindows/CVI compatibility: LabWindows/CVI 3.0 and later
Example
Refer to apps\daqmthread\daqMT.cws for an example of using the OpenFile function.