| blob | dffd1f61add786130d4f3b195cd93a8b2f712fde |
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3 .\" Copyright 1989 AT&T
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7 .TH TRUSS 1 "Jul 31, 2004"
8 .SH NAME
9 truss \- trace system calls and signals
10 .SH SYNOPSIS
11 .LP
12 .nf
13 \fBtruss\fR [\fB-fcaeildDE\fR] [\fB-\fR [tTvx] [!] \fIsyscall\fR ,...]
14 [\fB-\fR [sS] [!] \fIsignal\fR ,...] [\fB-\fR [mM] [!] \fIfault\fR ,...]
15 [\fB-\fR [rw] [!] \fIfd\fR ,...]
16 [\fB-\fR [uU] [!] \fIlib\fR ,... : [:] [!] \fIfunc\fR ,...]
17 [\fB-o\fR \fIoutfile\fR] \fIcommand\fR | \fB-p\fR \fIpid\fR[\fI/lwps\fR]...
18 .fi
20 .SH DESCRIPTION
21 .sp
22 .LP
23 The \fBtruss\fR utility executes the specified command and produces a trace of
24 the system calls it performs, the signals it receives, and the machine faults
25 it incurs. Each line of the trace output reports either the fault or signal
26 name or the system call name with its arguments and return value(s). System
27 call arguments are displayed symbolically when possible using defines from
28 relevant system headers. For any path name pointer argument, the pointed-to
29 string is displayed. Error returns are reported using the error code names
30 described in \fBIntro\fR(3). If, in the case of an error, the kernel reports a
31 missing privilege, a privilege name as described in \fBprivileges\fR(5) is
32 reported in square brackets (\fB[ ]\fR) after the error code name.
33 .sp
34 .LP
35 Optionally (see the \fB-u\fR option), \fBtruss\fR also produce an entry/exit
36 trace of user-level function calls executed by the traced process, indented to
37 indicate nesting.
38 .SH OPTIONS
39 .sp
40 .LP
41 For those options that take a list argument, the name \fBall\fR can be used as
42 a shorthand to specify all possible members of the list. If the list begins
43 with a \fB!\fR, the meaning of the option is negated (for example, exclude
44 rather than trace). Multiple occurrences of the same option can be specified.
45 For the same name in a list, subsequent options (those to the right) override
46 previous ones (those to the left).
47 .sp
48 .LP
49 The following options are supported:
50 .sp
51 .ne 2
52 .na
53 \fB\fB-a\fR\fR
54 .ad
55 .sp .6
56 .RS 4n
57 Shows the argument strings that are passed in each \fBexec()\fR system call.
58 .RE
60 .sp
61 .ne 2
62 .na
63 \fB\fB-c\fR\fR
64 .ad
65 .sp .6
66 .RS 4n
67 Counts traced system calls, faults, and signals rather than displaying the
68 trace line-by-line. A summary report is produced after the traced command
69 terminates or when \fBtruss\fR is interrupted. If \fB-f\fR is also specified,
70 the counts include all traced system calls, faults, and signals for child
71 processes.
72 .RE
74 .sp
75 .ne 2
76 .na
77 \fB\fB-d\fR\fR
78 .ad
79 .sp .6
80 .RS 4n
81 Includes a time stamp on each line of trace output. The time stamp appears as a
82 field containing \fIseconds\fR\|.\|\fIfraction\fR at the start of the line.
83 This represents a time in seconds relative to the beginning of the trace. The
84 first line of the trace output shows the base time from which the individual
85 time stamps are measured, both as seconds since the epoch (see \fBtime\fR(2))
86 and as a date string (see \fBctime\fR(3C) and \fBdate\fR(1)). The times that
87 are reported are the times that the event in question occurred. For all system
88 calls, the event is the completion of the system call, not the start of the
89 system call.
90 .RE
92 .sp
93 .ne 2
94 .na
95 \fB\fB-D\fR\fR
96 .ad
97 .sp .6
98 .RS 4n
99 Includes a time delta on each line of trace output. The value appears as a
100 field containing \fIseconds\fR\|.\|\fIfraction\fR and represents the elapsed
101 time for the \fBLWP\fR that incurred the event since the last reported event
102 incurred by that \fBLWP.\fR Specifically, for system calls, this is not the
103 time spent within the system call.
104 .RE
106 .sp
107 .ne 2
108 .na
109 \fB\fB-e\fR\fR
110 .ad
111 .sp .6
112 .RS 4n
113 Shows the environment strings that are passed in each \fBexec()\fR system call.
114 .RE
116 .sp
117 .ne 2
118 .na
119 \fB\fB-E\fR\fR
120 .ad
121 .sp .6
122 .RS 4n
123 Includes a time delta on each line of trace output. The value appears as a
124 field containing \fIseconds\fR\fB\&.\fR\fIfraction\fR and represents the
125 difference in time elapsed between the beginning and end of a system call.
126 .sp
127 In contrast to the \fB-D\fR option, this is the amount of time spent within
128 the system call.
129 .RE
131 .sp
132 .ne 2
133 .na
134 \fB\fB-f\fR\fR
135 .ad
136 .sp .6
137 .RS 4n
138 Follows all children created by \fBfork()\fR or \fBvfork()\fR and includes
139 their signals, faults, and system calls in the trace output. Normally, only the
140 first-level command or process is traced. When \fB-f\fR is specified, the
141 process-id is included with each line of trace output to indicate which process
142 executed the system call or received the signal.
143 .RE
145 .sp
146 .ne 2
147 .na
148 \fB\fB-i\fR\fR
149 .ad
150 .sp .6
151 .RS 4n
152 Does not display interruptible sleeping system calls. Certain system calls,
153 such as \fBopen()\fR and \fBread()\fR on terminal devices or pipes, can sleep
154 for indefinite periods and are interruptible. Normally, \fBtruss\fR reports
155 such sleeping system calls if they remain asleep for more than one second. The
156 system call is reported again a second time when it completes. The \fB-i\fR
157 option causes such system calls to be reported only once, when they complete.
158 .RE
160 .sp
161 .ne 2
162 .na
163 \fB\fB-l\fR\fR
164 .ad
165 .sp .6
166 .RS 4n
167 Includes the id of the responsible lightweight process (\fILWP\fR) with each
168 line of trace output. If \fB-f\fR is also specified, both the process-id and
169 the LWP-id are included.
170 .RE
172 .sp
173 .ne 2
174 .na
175 \fB\fB-m\fR [\fB!\fR]\fIfault\fR,...\fR
176 .ad
177 .sp .6
178 .RS 4n
179 Machine faults to trace or exclude. Those faults specified in the
180 comma-separated list are traced. Faults can be specified by name or number (see
181 \fB<sys/fault.h>\fR). If the list begins with a \fB!\fR, the specified faults
182 are excluded from the trace output. Default is \fB-mall\fR \fB-m\fR
183 \fB!fltpage\fR.
184 .RE
186 .sp
187 .ne 2
188 .na
189 \fB\fB-M\fR [\fB!\fR]\fIfault\fR,...\fR
190 .ad
191 .sp .6
192 .RS 4n
193 Machine faults that stop the process. The specified faults are added to the set
194 specified by \fB-m\fR. If one of the specified faults is incurred, \fBtruss\fR
195 leaves the process stopped and abandoned (see the \fB-T\fR option). Default is
196 \fB\fR\fB-M\fR\fB!all\fR.
197 .RE
199 .sp
200 .ne 2
201 .na
202 \fB\fB-o\fR \fIoutfile\fR\fR
203 .ad
204 .sp .6
205 .RS 4n
206 File to be used for the trace output. By default, the output goes to standard
207 error.
208 .RE
210 .sp
211 .ne 2
212 .na
213 \fB\fB-p\fR\fR
214 .ad
215 .sp .6
216 .RS 4n
217 Interprets the \fIcommand\fR arguments to \fBtruss\fR as a list of process-ids
218 for existing processes (see \fBps\fR(1)) rather than as a command to be
219 executed. \fBtruss\fR takes control of each process and begins tracing it
220 provided that the userid and groupid of the process match those of the user or
221 that the user is a privileged user. Users can trace only selected threads by
222 appending \fB/\fR\fIthread-id\fR to the process-id. Mutiple threads can be
223 selected using the \fB-\fR and \fB,\fR delimiters. For example \fB/1,2,7-9\fR
224 traces threads \fB1\fR, \fB2\fR, \fB7\fR, \fB8\fR, and \fB9\fR. Processes can
225 also be specified by their names in the \fB/proc\fR directory, for example,
226 \fB/proc/12345\fR.
227 .RE
229 .sp
230 .ne 2
231 .na
232 \fB\fB-r\fR [\fB!\fR]\fIfd\fR,...\fR
233 .ad
234 .sp .6
235 .RS 4n
236 Shows the full contents of the \fBI/O\fR buffer for each \fBread()\fR on any of
237 the specified file descriptors. The output is formatted 32 bytes per line and
238 shows each byte as an \fBASCII\fR character (preceded by one blank) or as a
239 2-character C language escape sequence for control characters such as
240 horizontal tab (\|\e\|t) and newline (\|\e\|n). If \fBASCII\fR interpretation
241 is not possible, the byte is shown in 2-character hexadecimal representation.
242 (The first 12 bytes of the \fBI/O\fR buffer for each traced \fBprint >read()\fR
243 are shown even in the absence of \fB-r\fR.) Default is
244 \fB\fR\fB-r\fR\fB!all\fR.
245 .RE
247 .sp
248 .ne 2
249 .na
250 \fB\fB-s\fR [\fB!\fR]\fIsignal\fR,...\fR
251 .ad
252 .sp .6
253 .RS 4n
254 Signals to trace or exclude. Those signals specified in the comma-separated
255 list are traced. The trace output reports the receipt of each specified signal,
256 even if the signal is being ignored (not blocked). (Blocked signals are not
257 received until they are unblocked.) Signals can be specified by name or number
258 (see \fB<sys/signal.h>\fR). If the list begins with a \fB!\fR, the specified
259 signals are excluded from the trace output. Default is \fB-sall\fR.
260 .RE
262 .sp
263 .ne 2
264 .na
265 \fB\fB-S\fR [\fB!\fR]\fIsignal\fR,...\fR
266 .ad
267 .sp .6
268 .RS 4n
269 Signals that stop the process. The specified signals are added to the set
270 specified by \fB-s\fR. If one of the specified signals is received, \fBtruss\fR
271 leaves the process stopped and abandoned (see the \fB-T\fR option). Default is
272 \fB\fR\fB-S\fR\fB!all\fR.
273 .RE
275 .sp
276 .ne 2
277 .na
278 \fB\fB-t\fR [\fB!\fR]\fIsyscall\fR,...\fR
279 .ad
280 .sp .6
281 .RS 4n
282 System calls to trace or exclude. Those system calls specified in the
283 comma-separated list are traced. If the list begins with a \fB!\fR, the
284 specified system calls are excluded from the trace output. Default is
285 \fB-tall\fR.
286 .RE
288 .sp
289 .ne 2
290 .na
291 \fB\fB-T\fR [\fB!\fR]\fIsyscall\fR,...\fR
292 .ad
293 .sp .6
294 .RS 4n
295 Specifies system calls that stop the process. The specified system calls are
296 added to the set specified by \fB-t\fR. If one of the specified system calls is
297 encountered, \fBtruss\fR leaves the process stopped and abandoned. That is,
298 \fBtruss\fR releases the process and exits but leaves the process in the
299 stopped state at completion of the system call in question. A debugger or other
300 process inspection tool (see \fBproc\fR(1)) can then be applied to the stopped
301 process. \fBtruss\fR can be reapplied to the stopped process with the same or
302 different options to continue tracing. Default is \fB\fR\fB-T\fR\fB!all\fR.
303 .sp
304 A process left stopped in this manner cannot be restarted by the application of
305 \fBkill\fR \fB-CONT\fR because it is stopped on an event of interest via
306 \fB/proc\fR, not by the default action of a stopping signal (see
307 \fBsignal.h\fR(3HEAD)). The \fBprun\fR(1) command described in \fBproc\fR(1)
308 can be used to set the stopped process running again.
309 .RE
311 .sp
312 .ne 2
313 .na
314 \fB\fB-u\fR
315 [\fB!\fR]\fIlib\fR,...\fB:\fR[\fB:\fR][\fB!\fR]\fIfunc\fR,\|.\|.\|.\fR
316 .ad
317 .sp .6
318 .RS 4n
319 User-level function call tracing. \fIlib\fR,\|.\|.\|. is a comma-separated list
320 of dynamic library names, excluding the ``\fB\&.so.\fR\fIn\fR'' suffix.
321 \fIfunc\fR,\|.\|.\|. is a comma-separated list of function names. In both cases
322 the names can include name-matching metacharacters \fB*\fR,\fB?\fR,\fB[]\fR
323 with the same meanings as those of \fBsh\fR(1) but as applied to the
324 library/function name spaces, not to files. An empty library or function list
325 defaults to \fB*\fR, trace all libraries or functions in a library. A leading
326 \fB!\fR on either list specifies an exclusion list, names of libraries or
327 functions not to be traced. Excluding a library excludes all functions in that
328 library; any function list following a library exclusion list is ignored.
329 .sp
330 A single \fB:\fR separating the library list from the function list means to
331 trace calls into the libraries from outside the libraries, but omit calls made
332 to functions in a library from other functions in the same library. A double
333 \fB:\|:\fR means to trace all calls, regardless of origin.
334 .sp
335 Library patterns do not match either the executable file or the dynamic linker
336 unless there is an exact match (\fBl*\fR does not match \fBld.so.1\fR). To
337 trace functions in either of these objects, the names must be specified
338 exactly, as in:
339 .sp
340 .in +2
341 .nf
342 \fBtruss -u a.out -u ld ...\fR
343 .fi
344 .in -2
345 .sp
347 \fBa.out\fR is the literal name to be used for this purpose; it does not stand
348 for the name of the executable file. Tracing \fBa.out\fR function calls implies
349 all calls (default is \fB::\fR).
350 .sp
351 Multiple \fB-u\fR options can be specified and they are honored left-to-right.
352 The id of the thread that performed the function call is included in the trace
353 output for the call. \fBtruss\fR searches the dynamic symbol table in each
354 library to find function names and also searches the standard symbol table if
355 it has not been stripped.
356 .RE
358 .sp
359 .ne 2
360 .na
361 \fB\fB-U\fR
362 [\fB!\fR]\fIlib\fR,\|.\|.\|.\|\fB:\fR[\fB:\fR][\fB!\fR]\fIfunc\fR,\|.\|.\|.\fR
363 .ad
364 .sp .6
365 .RS 4n
366 User-level function calls that stop the process. The specified functions are
367 added to the set specified by \fB-u\fR. If one of the specified functions is
368 called, \fBtruss\fR leaves the process stopped and abandoned (see the \fB-T\fR
369 option).
370 .RE
372 .sp
373 .ne 2
374 .na
375 \fB\fB-v\fR [\fB!\fR]\fIsyscall\fR,...\fR
376 .ad
377 .sp .6
378 .RS 4n
379 Verbose. Displays the contents of any structures passed by address to the
380 specified system calls (if traced by \fB-t\fR). Input values as well as values
381 returned by the operating system are shown. For any field used as both input
382 and output, only the output value is shown. Default is
383 \fB\fR\fB-v\fR\fB!all\fR.
384 .RE
386 .sp
387 .ne 2
388 .na
389 \fB\fB-w\fR [\fB!\fR]\fIfd\fR,...\fR
390 .ad
391 .sp .6
392 .RS 4n
393 Shows the contents of the I/O buffer for each \fBwrite()\fR on any of the
394 specified file descriptors (see the \fB-r\fR option). Default is
395 \fB\fR\fB-w\fR\fB!all\fR.
396 .RE
398 .sp
399 .ne 2
400 .na
401 \fB\fB-x\fR [\fB!\fR]\fIsyscall\fR,...\fR
402 .ad
403 .sp .6
404 .RS 4n
405 Displays the arguments to the specified system calls (if traced by \fB-t\fR) in
406 raw form, usually hexadecimal, rather than symbolically. This is for unredeemed
407 hackers who must see the raw bits to be happy. Default is
408 \fB\fR\fB-x\fR\fB!all\fR.
409 .RE
411 .sp
412 .LP
413 See \fIman pages section 2: System Calls\fR for system call names accepted by
414 the \fB-t\fR, \fB-T\fR, \fB-v\fR, and \fB-x\fR options. System call numbers are
415 also accepted.
416 .sp
417 .LP
418 If \fBtruss\fR is used to initiate and trace a specified command and if the
419 \fB-o\fR option is used or if standard error is redirected to a non-terminal
420 file, then \fBtruss\fR runs with hangup, interrupt, and quit signals ignored.
421 This facilitates tracing of interactive programs that catch interrupt and quit
422 signals from the terminal.
423 .sp
424 .LP
425 If the trace output remains directed to the terminal, or if existing processes
426 are traced (the \fB-p\fR option), then \fBtruss\fR responds to hangup,
427 interrupt, and quit signals by releasing all traced processes and exiting. This
428 enables the user to terminate excessive trace output and to release
429 previously-existing processes. Released processes continue normally, as though
430 they had never been touched.
431 .SH EXAMPLES
432 .LP
433 \fBExample 1 \fRTracing a Command
434 .sp
435 .LP
436 The following example produces a trace of the \fBfind\fR(1) command on the
437 terminal:
439 .sp
440 .in +2
441 .nf
442 example$ \fBtruss find . -print >find.out\fR
443 .fi
444 .in -2
445 .sp
447 .LP
448 \fBExample 2 \fRTracing Common System Calls
449 .sp
450 .LP
451 The following example shows only a trace of the open, close, read, and write
452 system calls:
454 .sp
455 .in +2
456 .nf
457 example$ \fBtruss -t open,close,read,write find . -print >find.out\fR
458 .fi
459 .in -2
460 .sp
462 .LP
463 \fBExample 3 \fRTracing a Shell Script
464 .sp
465 .LP
466 The following example produces a trace of the \fBspell\fR(1) command on the
467 file \fBtruss.out\fR:
469 .sp
470 .in +2
471 .nf
472 example$ \fBtruss -f -o truss.out spell \fIdocument\fR\fR
473 .fi
474 .in -2
475 .sp
477 .sp
478 .LP
479 \fBspell\fR is a shell script, so the \fB-f\fR flag is needed to trace not only
480 the shell but also the processes created by the shell. (The spell script runs a
481 pipeline of eight processes.)
483 .LP
484 \fBExample 4 \fRAbbreviating Output
485 .sp
486 .LP
487 The following example abreviates output:
489 .sp
490 .in +2
491 .nf
492 example$ \fBtruss nroff -mm \fIdocument\fR >nroff.out\fR
493 .fi
494 .in -2
495 .sp
497 .sp
498 .LP
499 because 97% of the output reports \fBlseek()\fR, \fBread()\fR, and
500 \fBwrite()\fR system calls. To abbreviate it:
502 .sp
503 .in +2
504 .nf
505 example$ \fBtruss -t !lseek,read,write nroff -mm \fIdocument\fR >nroff.out\fR
506 .fi
507 .in -2
508 .sp
510 .LP
511 \fBExample 5 \fRTracing Library Calls From Outside the C Library
512 .sp
513 .LP
514 The following example traces all user-level calls made to any function in the C
515 library from outside the C library:
517 .sp
518 .in +2
519 .nf
520 example$ \fBtruss -u libc ...\fR
521 .fi
522 .in -2
523 .sp
525 .LP
526 \fBExample 6 \fRTracing library calls from within the C library
527 .sp
528 .LP
529 The following example includes calls made to functions in the C library from
530 within the C library itself:
532 .sp
533 .in +2
534 .nf
535 example$ \fBtruss -u libc:: ...\fR
536 .fi
537 .in -2
538 .sp
540 .LP
541 \fBExample 7 \fRTracing Library Calls Other Than the C Library
542 .sp
543 .LP
544 The following example traces all user-level calls made to any library other
545 than the C library:
547 .sp
548 .in +2
549 .nf
550 example$ \fBtruss -u '*' -u !libc ...\fR
551 .fi
552 .in -2
553 .sp
555 .LP
556 \fBExample 8 \fRTracing \fBprintf\fR and \fBscanf\fR Function Calls
557 .sp
558 .LP
559 The following example traces all user-level calls to functions in the printf
560 and scanf family contained in the C library:
562 .sp
563 .in +2
564 .nf
565 example$ \fBtruss -u 'libc:*printf,*scanf' ...\fR
566 .fi
567 .in -2
568 .sp
570 .LP
571 \fBExample 9 \fRTracing Every User-level Function Call
572 .sp
573 .LP
574 The following example traces every user-level function call from anywhere to
575 anywhere:
577 .sp
578 .in +2
579 .nf
580 example$ \fBtruss -u a.out -u ld:: -u :: ...\fR
581 .fi
582 .in -2
583 .sp
585 .LP
586 \fBExample 10 \fRTracing a System Call Verbosely
587 .sp
588 .LP
589 The following example verbosely traces the system call activity of process #1,
590 \fBinit\fR(1M) (if you are a privileged user):
592 .sp
593 .in +2
594 .nf
595 example# \fBtruss -p -v all 1\fR
596 .fi
597 .in -2
598 .sp
600 .sp
601 .LP
602 Interrupting \fBtruss\fR returns \fBinit\fR to normal operation.
604 .SH FILES
605 .sp
606 .ne 2
607 .na
608 \fB\fB/proc/*\fR\fR
609 .ad
610 .RS 11n
611 Process files
612 .RE
614 .SH SEE ALSO
615 .sp
616 .LP
617 \fBdate\fR(1), \fBfind\fR(1), \fBproc\fR(1), \fBps\fR(1), \fBsh\fR(1),
618 \fBspell\fR(1), \fBinit\fR(1M), \fBIntro\fR(3), \fBexec\fR(2), \fBfork\fR(2),
619 \fBlseek\fR(2), \fBopen\fR(2), \fBread\fR(2), \fBtime\fR(2), \fBvfork\fR(2),
620 \fBwrite\fR(2), \fBctime\fR(3C), \fBsignal.h\fR(3HEAD), \fBproc\fR(4),
621 \fBattributes\fR(5), \fBprivileges\fR(5), \fBthreads\fR(5)
622 .sp
623 .LP
624 \fIman pages section 2: System Calls\fR
625 .SH NOTES
626 .sp
627 .LP
628 Some of the system calls described in \fIman pages section 2: System Calls\fR
629 differ from the actual operating system interfaces. Do not be surprised by
630 minor deviations of the trace output from the descriptions in that document.
631 .sp
632 .LP
633 Every machine fault (except a page fault) results in the posting of a signal to
634 the \fBLWP\fR that incurred the fault. A report of a received signal
635 immediately follows each report of a machine fault (except a page fault) unless
636 that signal is being blocked.
637 .sp
638 .LP
639 The operating system enforces certain security restrictions on the tracing of
640 processes. In particular, any command whose object file (\fBa.out\fR) cannot be
641 read by a user cannot be traced by that user; set-uid and set-gid commands can
642 be traced only by a privileged user. Unless it is run by a privileged user,
643 \fBtruss\fR loses control of any process that performs an \fBexec()\fR of a
644 set-id or unreadable object file; such processes continue normally, though
645 independently of \fBtruss\fR, from the point of the \fBexec()\fR.
646 .sp
647 .LP
648 To avoid collisions with other controlling processes, \fBtruss\fR does not
649 trace a process that it detects is being controlled by another process via the
650 \fB/proc\fR interface. This allows \fBtruss\fR to be applied to
651 \fBproc\fR(4)-based debuggers as well as to another instance of itself.
652 .sp
653 .LP
654 The trace output contains tab characters under the assumption that standard tab
655 stops are set (every eight positions).
656 .sp
657 .LP
658 The trace output for multiple processes or for a multithreaded process (one
659 that contains more than one \fBLWP)\fR is not produced in strict time order.
660 For example, a \fBread()\fR on a pipe can be reported before the corresponding
661 \fBwrite()\fR. For any one \fBLWP\fR (a traditional process contains only one),
662 the output is strictly time-ordered.
663 .sp
664 .LP
665 When tracing more than one process, \fBtruss\fR runs as one controlling process
666 for each process being traced. For the example of the \fBspell\fR command shown
667 above, \fBspell\fR itself uses 9 process slots, one for the shell and 8 for the
668 8-member pipeline, while \fBtruss\fR adds another 9 processes, for a total of
669 18.
670 .sp
671 .LP
672 Not all possible structures passed in all possible system calls are displayed
673 under the \fB-v\fR option.