trace.5

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)trace.5	8.1	9/11/90
.TH trace 5
.SH Name
trace \- system call tracer device
.SH Description
.NXR "trace file"
.NXR "system call tracer device"
.NXAM "open system call" "trace file"
.NXAM "close system call" "trace file"
.NXAM "read system call" "trace file"
.NXAM "ioctl system call" "trace file"
.NXAM "select system call" "trace file"
The file
.PN /dev/trace
is the system call trace device. It supports the following system calls:
.PN open ,
.PN close ,
.PN read ,
.PN ioctl ,
and
.PN select .
The device supports 16 (configurable in 
.PN sys/systrace.h
as TR_USRS)
simultaneous users. It uses an 8192-byte buffer for trace records.
The choice of which system calls to trace is
done with the 
.PN ioctl
system
call. The 
.PN select
call is used for efficient reading of the device.
The
.PN select
call
uses an 8192-byte buffer and returns
when the buffer is 60% full.
It is required that the user use a buffer the same size
as the system buffer
size defined in 
.PN sys/systrace.h
as TR_BUFSIZE.
All 
.PN ioctl
operations are defined in the header 
file, 
.PN sys/systrace.h .
The 
.PN ioctl
calls are:
.PP
.TS
tab (@) ;
lfHB lfHB
lfR lfR .
_
.sp 4p
ioctl@arg (pointer to)
.sp 4p
_
.sp 6p
IOTR_GETOFF@int a
IOTR_GETON@int a
IOTR_GETALL@int a
IOTR_GETPIDS@int a[10]
IOTR_GETUIDS@int a[10]
IOTR_GETSYSC@int a[10]
IOTR_GETPGRP@int a[10]
IOTR_SETOFF@int a
IOTR_SETON@int a
IOTR_SETALL@int a
IOTR_SETPIDS@int a[10]
IOTR_SETUIDS@int a[10]
IOTR_SETSYSC@int a[10]
IOTR_SETPGRP@int a[10]
.sp 6p
_
.TE
.PP
.SH Examples
A prototype example (with missing parts):
.EX 0
char cmd[BUFSIZ],buf[TR_BUFSIZ];
int pgrp[10],i;
fd = open("/dev/trace",0);      /* open the device */
pgrp[0] = dofork(cmd);          /* fork the command to trace */
for (i=1;i<TR_PGRP;i++)         /* dofork sleeps 2 seconds while */
        pgrp[i] = 0;            /* we set up to do the trace */
i = ioctl(fd,IOTR_SETPGRP,pgrp);/* set up for the trace */
/* select code goes here */
read(fd,buf,sizeof(buf));
.EE
.ad
.SH See Also
trace(1), close(2), ioctl(2), open(2), read(2), select(2)