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+.TH FD2PATH 2
+.SH NAME
+fd2path \- return file name associated with file descriptor
+.SH SYNOPSIS
+.B #include <u.h>
+.br
+.B #include <libc.h>
+.PP
+.B
+int fd2path(int fd, char *buf, int nbuf)
+.SH DESCRIPTION
+As described in
+.IR intro (2),
+the kernel stores a rooted path name with every open file or directory;
+typically, it is the name used in the original access of the file.
+.I Fd2path
+returns the path name associated with open file descriptor
+.IR fd .
+Up to
+.I nbuf
+bytes of the name are stored in
+.IR buf ;
+if the name is too long, it will be silently truncated at a UTF-8
+character boundary.
+The name is always null-terminated.
+The return value of
+.I fd2path
+will be zero unless an error occurs.
+.PP
+Changes to the underlying name space do not update the path name
+stored with the file descriptor.
+Therefore,
+the path returned by
+.I fd2path
+may no longer refer to the same file (or indeed any file)
+after some component directory or file in the path has been removed, renamed
+or rebound.
+.PP
+As an example,
+.IR getwd (2)
+is implemented by opening
+.B .
+and executing
+.I fd2path
+on the resulting file descriptor.
+.SH SOURCE
+.B /sys/src/libc/9syscall
+.SH SEE ALSO
+.IR bind (1),
+.IR ns (1),
+.IR bind (2),
+.IR intro (2),
+.IR getwd (2),
+.IR proc (3)
+.SH DIAGNOSTICS
+Sets
+.IR errstr .