man -f/-k [keyword]在fedora 29 中报错nothing appropriate

[root@localhost tmp]# man -k aioaio (7)       - POSIX asynchronous I/O overviewaio.h (0p)      - asynchronous input and outputaio_cancel (3)    - cancel an outstanding asynchronous I/O requestaio_cancel (3p)   - cancel an asynchronous I/O requestaio_error (3)    - get error status of asynchronous I/O operationaio_error (3p)    - retrieve errors status for an asynchronous I/O operationaio_fsync (3)    - asynchronous file synchronizationaio_fsync (3p)    - asynchronous file synchronizationaio_init (3)     - asynchronous I/O initializationaio_read (3)     - asynchronous readaio_read (3p)    - asynchronous read from a fileaio_return (3)    - get return status of asynchronous I/O operationaio_return (3p)   - retrieve return status of an asynchronous I/O operationaio_suspend (3)   - wait for asynchronous I/O operation or timeoutaio_suspend (3p)   - wait for an asynchronous I/O requestaio_write (3)    - asynchronous writeaio_write (3p)    - asynchronous write to a file