I have a FILE returned by a call to fopen I need to get a file descriptor from it to make calls like fsync fd on it What s the function to get a file descriptor from a file pointer

The proper function is int fileno FILE stream It can be found in lt stdio h gt and is a POSIX standard but not standard C

Even if fileno FILE may return a file descriptor be VERY careful not to bypass stdio s buffer If there is buffer data either read or unflushed write reads writes from the file descriptor might give you unexpected results To answer one of the side questions to convert a file descriptor to a FILE pointer use fdopen 3

[c] How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?

The proper function is int fileno(FILE *stream). It can be found in <stdio.h>, and is a POSIX standard but not standard C.

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