mention readlinkat

Author: Vladimir Kotal

file-api.tex

@@ -985,6 +985,7 @@
 \item \emph{\texttt{bufsz}} is typically set as 1 byte less than the buffer
 size to accommodate the terminating \texttt{NULL} character.
 \item See \example{readlink/readlink.c} and fix the problem therein.
+\item There is also \texttt{readlinkat()} that operates on a file descriptor.
 \end{itemize}
 
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