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.Dd January 6, 2020
.Dt PROC_FDWALK 3PROC
.Os
.Sh NAME
.Nm proc_fdwalk
.Nd walk the open file descriptors for a process
.Sh SYNOPSIS
.Lb libproc
.In libproc.h
.Ft int
.Fo proc_fdwalk
.Fa "pid_t pid"
.Fa "proc_fdwalk_f *func"
.Fa "void *arg"
.Fc
.Sh DESCRIPTION
The
.Fn proc_fdwalk
function walks all file descriptors currently open in the process with ID
.Fa pid
and calls the callback function
.Fa func
once for each file descriptor with the user-specified
.Fa arg .
The definition of
.Vt proc_fdwalk_f
is available in
.Xr libproc 3LIB .
.Pp
.Fa func
will be called once for each file descriptor and will have its first
argument filled in with the contents of the corresponding
.Pa /proc
.Sy fdinfo
file for the file descriptor.
.Pp
The return value of the caller's
.Fa func
function determines whether or not iteration will continue.
If
.Fa func
returns a non-zero value, then iteration will terminate and that
return value will be returned to the caller.
To distinguish between system errors and caller errors, it is recommended that
the function only return positive integers in the event of an error.
.Sh RETURN VALUES
Upon successful completion, the
.Fn proc_fdwalk
function returns
.Sy 0 .
Otherwise,
.Sy -1
is returned and
.Sy errno
is updated to reflect the error that occurred.
.Sh ERRORS
In addition to the errors listed below, the
.Fn proc_fdwalk
function may fail for the same reasons as the
.Xr opendir 3C ,
.Xr readdir 3C ,
and
.Xr malloc 3C
functions.
.Sh INTERFACE STABILITY
.Sy Uncommitted
.Sh MT-LEVEL
.Sy MT-Safe
.Sh SEE ALSO
.Xr malloc 3C ,
.Xr opendir 3C ,
.Xr readdir 3C ,
.Xr libproc 3LIB ,
.Xr proc 4