Differential D21206 Diff 60767 lib/libc/stdlib/fdwalk.3

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lib/libc/stdlib/fdwalk.3

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				.\" Copyright (c) 2019 Justin Hibbits
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				.\" $FreeBSD$
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				.Dd August 9, 2019
				.Dt FDWALK 3
				.Os
				.Sh NAME
				.Nm fdwalk
				.Nd iterate over open file descriptors
				.Sh LIBRARY
				.Lb libc
				.Sh SYNOPSIS
				.In stdlib.h
				.Ft int
				.Fn fdwalk "int (cb)(void , int)" "void *cbd"
				.Sh DESCRIPTION
				The
				.Nm
				function walks the list of currently open file descriptors and the
				.Ar cb
				kibUnsubmitted Done Inline Actions and _calls_ the callback kib: and _calls_ the callback
				callback on each descriptor.
				The
				.Nm
				function passes the
				.Ar cbd
				argument into the callback, along with each file descriptor.
				If
				.Ar cbd
				returns non-zero, iteration over the list is terminated and the return value
				from
				.Ar cbd
				is returned up to the caller as the return value of
				.Nm .
				kibUnsubmitted Done Inline Actions New line for new sentence. malloc(3) etc should be typesetted with .Xr. kib: New line for new sentence. malloc(3) etc should be typesetted with .Xr.
				.Sh RETURN VALUES
				The
				.Nm
				kibUnsubmitted Done Inline Actions Not only new fds not handled (really they could be handled depending on the value), but also closed and thus invalid fds might be passed to callback. The man page lacks explanation of the interface for callback. In particular, what the return value means and how callback should handle errno to make the return state of fdwalk(3) parseable. kib: Not only new fds not handled (really they could be handled depending on the value), but also…
				function will return 0 on success, or the return value of the last call to the
				callback.
				No errors are defined for it.
				kibUnsubmitted Done Inline Actions This is not quite true. Also, on internal errors from malloc(3) or sysctl(3), you return -1 and errno contains some code. Later you state 'errors are passed through' but I am not sure that this can be understood without looking at the code. kib: This is not quite true. Also, on internal errors from malloc(3) or sysctl(3), you return -1…
				All errors are passed through from
				.Xr sysctl 3 ,
				.Xr malloc 3
				and the callback.
				.Sh SEE ALSO
				.Xr closefrom 2 ,
				.Xr kinfo_getfile 3
				.Sh HISTORY
				The
				.Nm
				function first appeared in SunOS.
				.Sh BUGS
				The
				.Nm
				function is potentially not thread safe.
				It uses
				.Xr malloc 3
				and
				.Xr sysctl 3
				behind the scenes.
				It also only takes a snapshot, so any file descriptors created or removed
				after the snapshot is taken, either in another thread or in the callback
				function, are not handled.