1  .TH rtapi_open_as_root "3rtapi" "" "LinuxCNC Documentation" "RTAPI"
 2  .SH NAME
 3  
 4  rtapi_open_as_root \- Open a file with "root" privilege
 5  
 6  .SH SYNTAX
 7  .nf
 8  .B #include <rtapi.h>
 9  .HP
10  .BI "int rtapi_open_as_root(const char " *filename ", int " "flags)"
11  .fi
12  .SH ARGUMENTS
13  .IP \fIfilename\fR
14  The filename to open, as in \fBopen(2)\fR.  Note that rtapi has no well-defined
15  "current directory", so this should be an absolute path, but this is not
16  enforced.
17  .IP \fIflags\fR
18  The open flags, as in \fBopen(2)\fR.  Should never include bits that open or
19  create files (e.g., O_CREAT, O_APPEND, etc) as this API is not intended for
20  creating or writing files, but this is not enforced.
21  
22  .SH DESCRIPTION
23  In "uspace" realtime, root privileges are dropped whenever possible.  This API
24  temporarily switches on root priveleges to open a file, and switches them
25  off before returning.  This can be useful for example when accessing device
26  nodes or memory-mapped I/O.
27  
28  In the case of PCI devices on x86 and x86-64 systems, prefer the linux-style
29  PCI interfaces provided in \fB<rtapi_pci.h>\fR.
30  
31  .SH RETURN VALUE
32  In case of success, the nonnegative file descriptor opened.  If the caller does
33  not close it, it remains open until rtapi_app exits.
34  
35  In case of failure, a negative errno value.
36  
37  .SH REALTIME CONSIDERATIONS
38  Call only from realtime initcode in "uspace" realtime.
39  
40  .SH SEE ALSO
41  \fBopen(2)\fR, \fBrtapi_pci(3)\fR