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Consequently, using any other values for pos will result in undefined behavior and should be avoided.
Noncompliant Code Example
The following This noncompliant code example attempts to read three values from a file and then set the cursor position back to the beginning of the file and return to the caller.
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However, because only the return value of a fgetpos() call is a valid argument to fsetpos(); , passing an fpos_t value that was created in any other way may not work. It is possible that the position will be set to an arbitrary location in the file.
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