.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-.\"
-.\" $Id$
-.\"
.de CW
.sp
.nf
.fi
.sp
..
-.TH STRACE 1 "2003-01-21"
+.\" Macro IX is not defined in the groff macros
+.if \n(.g \{\
+. de IX
+..
+.\}
+.TH STRACE 1 "2010-03-30"
.SH NAME
strace \- trace system calls and signals
.SH SYNOPSIS
.B strace
-[
-.B \-dffhiqrtttTvxx
-]
-[
-.BI \-a column
-]
-[
-.BI \-e expr
-]
-\&...
-[
-.BI \-o file
-]
-[
-.BI \-p pid
-]
-\&...
-[
-.BI \-s strsize
-]
-[
-.BI \-u username
-]
-[
-.BI \-E var=val
-]
-\&...
-[
-.BI \-E var
-]
-\&...
-[
-.I command
-[
-.I arg
-\&...
-]
-]
+[\fB-CdffhikqrtttTvVxxy\fR]
+[\fB-I\fIn\fR]
+[\fB-b\fIexecve\fR]
+[\fB-e\fIexpr\fR]...
+[\fB-a\fIcolumn\fR]
+[\fB-o\fIfile\fR]
+[\fB-s\fIstrsize\fR]
+[\fB-P\fIpath\fR]... \fB-p\fIpid\fR... /
+[\fB-D\fR]
+[\fB-E\fIvar\fR[=\fIval\fR]]... [\fB-u\fIusername\fR]
+\fIcommand\fR [\fIargs\fR]
.sp
.B strace
-.B \-c
-[
-.BI \-e expr
-]
-\&...
-[
-.BI \-O overhead
-]
-[
-.BI \-S sortby
-]
-[
-.I command
-[
-.I arg
-\&...
-]
-]
+\fB-c\fR[\fBdf\fR]
+[\fB-I\fIn\fR]
+[\fB-b\fIexecve\fR]
+[\fB-e\fIexpr\fR]...
+[\fB-O\fIoverhead\fR]
+[\fB-S\fIsortby\fR] \fB-p\fIpid\fR... /
+[\fB-D\fR]
+[\fB-E\fIvar\fR[=\fIval\fR]]... [\fB-u\fIusername\fR]
+\fIcommand\fR [\fIargs\fR]
.SH DESCRIPTION
.IX "strace command" "" "\fLstrace\fR command"
.LP
.LP
Each line in the trace contains the system call name, followed
by its arguments in parentheses and its return value.
-An example from stracing the command ``cat /dev/null'' is:
+An example from stracing the command "cat /dev/null" is:
.CW
open("/dev/null", O_RDONLY) = 3
.CE
Errors (typically a return value of \-1) have the errno symbol
and error string appended.
.CW
-open("/foo/bar", O_RDONLY) = -1 ENOENT (No such file or directory)
+open("/foo/bar", O_RDONLY) = \-1 ENOENT (No such file or directory)
.CE
-Signals are printed as a signal symbol and a signal string.
-An excerpt from stracing and interrupting the command ``sleep 666'' is:
+Signals are printed as signal symbol and decoded siginfo structure.
+An excerpt from stracing and interrupting the command "sleep 666" is:
.CW
sigsuspend([] <unfinished ...>
---- SIGINT (Interrupt) ---
+--- SIGINT {si_signo=SIGINT, si_code=SI_USER, si_pid=...} ---
+++ killed by SIGINT +++
.CE
+If a system call is being executed and meanwhile another one is being called
+from a different thread/process then
+.B strace
+will try to preserve the order of those events and mark the ongoing call as
+being
+.IR unfinished .
+When the call returns it will be marked as
+.IR resumed .
+.CW
+[pid 28772] select(4, [3], NULL, NULL, NULL <unfinished ...>
+[pid 28779] clock_gettime(CLOCK_REALTIME, {1130322148, 939977000}) = 0
+[pid 28772] <... select resumed> ) = 1 (in [3])
+.CE
+Interruption of a (restartable) system call by a signal delivery is processed
+differently as kernel terminates the system call and also arranges its
+immediate reexecution after the signal handler completes.
+.CW
+read(0, 0x7ffff72cf5cf, 1) = ? ERESTARTSYS (To be restarted)
+--- SIGALRM ... ---
+rt_sigreturn(0xe) = 0
+read(0, "", 1) = 0
+.CE
Arguments are printed in symbolic form with a passion.
-This example shows the shell performing ``>>xyzzy'' output redirection:
+This example shows the shell performing ">>xyzzy" output redirection:
.CW
open("xyzzy", O_WRONLY|O_APPEND|O_CREAT, 0666) = 3
.CE
-Here the three argument form of open is decoded by breaking down the
+Here the third argument of open is decoded by breaking down the
flag argument into its three bitwise-OR constituents and printing the
mode value in octal by tradition. Where traditional or native
usage differs from ANSI or POSIX, the latter forms are preferred.
Structure pointers are dereferenced and the members are displayed
as appropriate. In all cases arguments are formatted in the most C-like
fashion possible.
-For example, the essence of the command ``ls \-l /dev/null'' is captured as:
+For example, the essence of the command "ls \-l /dev/null" is captured as:
.CW
lstat("/dev/null", {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 3), ...}) = 0
.CE
-Notice how the `struct stat' argument is dereferenced and how each member is
+Notice how the 'struct stat' argument is dereferenced and how each member is
displayed symbolically. In particular, observe how the st_mode member
is carefully decoded into a bitwise-OR of symbolic and numeric values.
Also notice in this example that the first argument to lstat is an input
to the system call and the second argument is an output. Since output
arguments are not modified if the system call fails, arguments may not
-always be dereferenced. For example, retrying the ``ls \-l'' example
+always be dereferenced. For example, retrying the "ls \-l" example
with a non-existent file produces the following line:
.CW
-lstat("/foo/bar", 0xb004) = -1 ENOENT (No such file or directory)
+lstat("/foo/bar", 0xb004) = \-1 ENOENT (No such file or directory)
.CE
In this case the porch light is on but nobody is home.
.LP
.I strsize
(32 by default) bytes of strings are printed;
longer strings have an ellipsis appended following the closing quote.
-Here is a line from ``ls \-l'' where the
+Here is a line from "ls \-l" where the
.B getpwuid
library routine is reading the password file:
.CW
.CE
While structures are annotated using curly braces, simple pointers
and arrays are printed using square brackets with commas separating
-elements. Here is an example from the command ``id'' on a system with
+elements. Here is an example from the command "id" on a system with
supplementary group ids:
.CW
getgroups(32, [100, 0]) = 2
.CE
Here the second argument represents the full set of all signals.
.SH OPTIONS
+.SS Output format
.TP 12
.TP
-.B \-c
-Count time, calls, and errors for each system call and report a
-summary on program exit.
+.BI "\-a " column
+Align return values in a specific column (default column 40).
.TP
-.B \-d
-Show some debugging output of
-.B strace
-itself on the standard error.
+.B \-i
+Print the instruction pointer at the time of the system call.
.TP
-.B \-f
-Trace child processes as they are created by currently traced
-processes as a result of the
-.BR fork (2)
-system call. The new process is
-attached to as soon as its pid is known (through the return value of
-.BR fork (2)
-in the parent process). This means that such children may run
-uncontrolled for a while (especially in the case of a
-.BR vfork (2)),
-until the parent is scheduled again to complete its
-.RB ( v ) fork (2)
-call.
-If the parent process decides to
-.BR wait (2)
-for a child that is currently
-being traced, it is suspended until an appropriate child process either
-terminates or incurs a signal that would cause it to terminate (as
-determined from the child's current signal disposition).
+.B \-k
+Print the execution stack trace of the traced processes after each system call (experimental).
+This option is available only if
+.B strace
+is built with libunwind.
.TP
-.B \-ff
-If the
-.B \-o
+.BI "\-o " filename
+Write the trace output to the file
.I filename
-option is in effect, each processes trace is written to
+rather than to stderr.
+Use
.I filename.pid
-where pid is the numeric process id of each process.
-.TP
-.B \-F
-Attempt to follow
-.BR vfork s.
-(On SunOS 4.x, this is accomplished with
-some dynamic linking trickery. On Linux, it requires some kernel
-functionality not yet in the standard kernel.) Otherwise,
-.BR vfork s
-will
-not be followed even if
-.B \-f
-has been given.
-.TP
-.B \-h
-Print the help summary.
-.TP
-.B \-i
-Print the instruction pointer at the time of the system call.
+if
+.B \-ff
+is used.
+If the argument begins with '|' or with '!' then the rest of the
+argument is treated as a command and all output is piped to it.
+This is convenient for piping the debugging output to a program
+without affecting the redirections of executed programs.
.TP
.B \-q
Suppress messages about attaching, detaching etc. This happens
automatically when output is redirected to a file and the command
is run directly instead of attaching.
.TP
+.B \-qq
+If given twice, suppress messages about process exit status.
+.TP
.B \-r
Print a relative timestamp upon entry to each system call. This
records the time difference between the beginning of successive
system calls.
.TP
+.BI "\-s " strsize
+Specify the maximum string size to print (the default is 32). Note
+that filenames are not considered strings and are always printed in
+full.
+.TP
.B \-t
Prefix each line of the trace with the time of day.
.TP
of seconds since the epoch.
.TP
.B \-T
-Show the time spent in system calls. This records the time
+Show the time spent in system calls. This records the time
difference between the beginning and the end of each system call.
.TP
-.B \-v
-Print unabbreviated versions of environment, stat, termios, etc.
-calls. These structures are very common in calls and so the default
-behavior displays a reasonable subset of structure members. Use
-this option to get all of the gory details.
-.TP
-.B \-V
-Print the version number of
-.BR strace .
-.TP
.B \-x
Print all non-ASCII strings in hexadecimal string format.
.TP
.B \-xx
Print all strings in hexadecimal string format.
.TP
-.BI "\-a " column
-Align return values in a specific column (default column 40).
+.B \-y
+Print paths associated with file descriptor arguments.
+.TP
+.B \-yy
+Print protocol specific information associated with socket file descriptors.
+.SS Statistics
+.TP 12
+.TP
+.B \-c
+Count time, calls, and errors for each system call and report a summary on
+program exit. On Linux, this attempts to show system time (CPU time spent
+running in the kernel) independent of wall clock time. If
+.B \-c
+is used with
+.B \-f
+or
+.B \-F
+, only aggregate totals for all traced processes are kept.
+.TP
+.B \-C
+Like
+.B \-c
+but also print regular output while processes are running.
+.TP
+.BI "\-O " overhead
+Set the overhead for tracing system calls to
+.I overhead
+microseconds.
+This is useful for overriding the default heuristic for guessing
+how much time is spent in mere measuring when timing system calls using
+the
+.B \-c
+option. The accuracy of the heuristic can be gauged by timing a given
+program run without tracing (using
+.BR time (1))
+and comparing the accumulated
+system call time to the total produced using
+.BR \-c .
+.TP
+.BI "\-S " sortby
+Sort the output of the histogram printed by the
+.B \-c
+option by the specified criterion. Legal values are
+.BR time ,
+.BR calls ,
+.BR name ,
+and
+.B nothing
+(default is
+.BR time ).
+.TP
+.B \-w
+Summarise the time difference between the beginning and end of
+each system call. The default is to summarise the system time.
+.SS Filtering
+.TP 12
.TP
.BI "\-e " expr
A qualifying expression which modifies which events to trace
or how to trace them. The format of the expression is:
.RS 15
.IP
-[\fIqualifier\fB=\fR][\fB!\fR]\fIvalue1\fR[\fB,\fIvalue2\fR]...
+[\,\fIqualifier\/\fB=\fR][\fB!\fR]\,\fIvalue1\/\fR[\fB,\,\fIvalue2\/\fR]...
.RE
.IP
where
.BR raw ,
.BR signal ,
.BR read ,
+.BR write ,
or
-.B write
+.B fault
and
.I value
is a qualifier-dependent symbol or number. The default
qualifier is
.BR trace .
Using an exclamation mark negates the set of values. For example,
-.B \-eopen
+.BR \-e "\ " open
means literally
-.B "\-e trace=open"
+.BR \-e "\ " trace = open
which in turn means trace only the
.B open
system call. By contrast,
-.B "\-etrace=!open"
+.BR \-e "\ " trace "=!" open
means to trace every system call except
.BR open .
In addition, the special values
expansion even inside quoted arguments. If so, you must escape
the exclamation point with a backslash.
.TP
-.BI "\-e trace=" set
+\fB\-e\ trace\fR=\,\fIset\fR
Trace only the specified set of system calls. The
.B \-c
option is useful for determining which system calls might be useful
to trace. For example,
-.B trace=open,close,read,write
+.BR trace = open,close,read,write
means to only
trace those four system calls. Be careful when making inferences
about the user/kernel boundary if only a subset of system calls
are being monitored. The default is
-.BR trace=all .
+.BR trace = all .
.TP
-.B "\-e trace=file"
+.BR "\-e\ trace" = file
Trace all system calls which take a file name as an argument. You
can think of this as an abbreviation for
-.BR "\-e\ trace=open,stat,chmod,unlink," ...
+.BR "\-e\ trace" = open , stat , chmod , unlink ,...
which is useful to seeing what files the process is referencing.
Furthermore, using the abbreviation will ensure that you don't
accidentally forget to include a call like
.B lstat
in the list. Betchya woulda forgot that one.
.TP
-.B "\-e trace=process"
+.BR "\-e\ trace" = process
Trace all system calls which involve process management. This
is useful for watching the fork, wait, and exec steps of a process.
.TP
-.B "\-e trace=network"
+.BR "\-e\ trace" = network
Trace all the network related system calls.
.TP
-.B "\-e trace=signal"
+.BR "\-e\ trace" = signal
Trace all signal related system calls.
.TP
-.B "\-e trace=ipc"
+.BR "\-e\ trace" = ipc
Trace all IPC related system calls.
.TP
-.BI "\-e abbrev=" set
+.BR "\-e\ trace" = desc
+Trace all file descriptor related system calls.
+.TP
+.BR "\-e\ trace" = memory
+Trace all memory mapping related system calls.
+.TP
+\fB\-e\ abbrev\fR=\,\fIset\fR
Abbreviate the output from printing each member of large structures.
The default is
-.BR abbrev=all .
+.BR abbrev = all .
The
.B \-v
option has the effect of
-.BR abbrev=none .
+.BR abbrev = none .
.TP
-.BI "\-e verbose=" set
+\fB\-e\ verbose\fR=\,\fIset\fR
Dereference structures for the specified set of system calls. The
default is
-.BR verbose=all .
+.BR verbose = all .
.TP
-.BI "\-e raw=" set
+\fB\-e\ raw\fR=\,\fIset\fR
Print raw, undecoded arguments for the specified set of system calls.
This option has the effect of causing all arguments to be printed
in hexadecimal. This is mostly useful if you don't trust the
decoding or you need to know the actual numeric value of an
argument.
.TP
-.BI "\-e signal=" set
+\fB\-e\ signal\fR=\,\fIset\fR
Trace only the specified subset of signals. The default is
-.BR signal=all .
+.BR signal = all .
For example,
-.B signal=!SIGIO
+.B signal "=!" SIGIO
(or
-.BR signal=!io )
+.BR signal "=!" io )
causes SIGIO signals not to be traced.
.TP
-.BI "\-e read=" set
+\fB\-e\ read\fR=\,\fIset\fR
Perform a full hexadecimal and ASCII dump of all the data read from
file descriptors listed in the specified set. For example, to see
-all input activity on file descriptors 3 and 5 use
-.BR "\-e read=3,5" .
+all input activity on file descriptors
+.I 3
+and
+.I 5
+use
+\fB\-e\ read\fR=\,\fI3\fR,\fI5\fR.
Note that this is independent from the normal tracing of the
.BR read (2)
system call which is controlled by the option
-.BR "\-e trace=read" .
+.BR -e "\ " trace = read .
.TP
-.BI "\-e write=" set
+\fB\-e\ write\fR=\,\fIset\fR
Perform a full hexadecimal and ASCII dump of all the data written to
file descriptors listed in the specified set. For example, to see
-all output activity on file descriptors 3 and 5 use
-.BR "\-e write=3,5" .
+all output activity on file descriptors
+.I 3
+and
+.I 5
+use
+\fB\-e\ write\fR=\,\fI3\fR,\,\fI5\fR.
Note that this is independent from the normal tracing of the
.BR write (2)
system call which is controlled by the option
-.BR "\-e trace=write" .
+.BR -e "\ " trace = write .
+.TP
+\fB\-e\ fault\fR=\,\fIset\/\fR[:\fBerror\fR=\,\fIerrno\/\fR][:\fBwhen\fR=\,\fIexpr\/\fR]
+Perform a syscall fault injection for the specified set of syscalls.
+When a fault is injected into a syscall invocation, the syscall number
+is replaced by -1 which corresponds to an invalid syscall.
+
+If an error code is specified using a symbolic
+.I errno
+value like
+.B ENOSYS
+or a numeric value within 1..4095 range, this error code overrides
+the default error code returned by the kernel, which is traditionally
+.B ENOSYS
+for invalid syscall numbers on most architectures.
+
+Unless a :\fBwhen\fR=\,\fIexpr\fR subexpression is specified,
+a fault is injected into every invocation of each syscall from the
+.IR set .
+
+The format of the subexpression is one of the following:
+.RS
+.IP "" 2
+.I first
+.RS 4
+For every syscall from the
+.IR set ,
+perform a syscall fault injection for the syscall invocation number
+.I first
+only.
+.RE
+.IP "" 2
+\fIfirst\/\fB+\fR
+.RS 4
+For every syscall from the
+.IR set ,
+perform syscall fault injections for the syscall invocation number
+.I first
+and all subsequent invocations.
+.RE
+.IP "" 2
+\fIfirst\/\fB+\fIstep\fR
+.RS 4
+For every syscall from the
+.IR set ,
+perform syscall fault injections for syscall invocations number
+.IR first ,
+.IR first + step ,
+.IR first + step + step ,
+and so on.
+.RE
+.RE
+.IP
+For example, to fail each third and subsequent chdir syscalls with
+.BR ENOENT ,
+use
+\fB\-e\ fault\fR=\,\fIchdir\/\fR:\fBerror\fR=\,\fIENOENT\/\fR:\fBwhen\fR=\,\fI3\/\fB+\fR.
+
+The valid range for numbers
+.I first
+and
+.I step
+is 1..65535.
+
+If a fault expression contains multiple
+.BR error =
+specifications, the last one takes precedence.
+Likewise, if a fault expression contains multiple
+.BR when =
+specifications, the last one takes precedence.
+
+Accounting of syscalls that are subject to fault injection
+is done per syscall and per tracee.
+
+Specification of syscall fault injection can be combined
+with other syscall filtering options, for example,
+\fB\-P \fI/dev/urandom \fB\-e fault\fR=\,\fIall\/\fR:\fBerror\fR=\,\fIENOENT\fR.
+.TP
+.BI "\-P " path
+Trace only system calls accessing
+.IR path .
+Multiple
+.B \-P
+options can be used to specify several paths.
.TP
-.BI "\-o " filename
-Write the trace output to the file
+.B \-v
+Print unabbreviated versions of environment, stat, termios, etc.
+calls. These structures are very common in calls and so the default
+behavior displays a reasonable subset of structure members. Use
+this option to get all of the gory details.
+.SS Tracing
+.TP 12
+.TP
+.BI "\-b " syscall
+If specified syscall is reached, detach from traced process.
+Currently, only
+.I execve
+syscall is supported. This option is useful if you want to trace
+multi-threaded process and therefore require -f, but don't want
+to trace its (potentially very complex) children.
+.TP
+.B \-D
+Run tracer process as a detached grandchild, not as parent of the
+tracee. This reduces the visible effect of
+.B strace
+by keeping the tracee a direct child of the calling process.
+.TP
+.B \-f
+Trace child processes as they are created by currently traced
+processes as a result of the
+.BR fork (2),
+.BR vfork (2)
+and
+.BR clone (2)
+system calls. Note that
+.B \-p
+.I PID
+.B \-f
+will attach all threads of process PID if it is multi-threaded,
+not only thread with thread_id = PID.
+.TP
+.B \-ff
+If the
+.B \-o
.I filename
-rather than to stderr.
-Use
+option is in effect, each processes trace is written to
.I filename.pid
-if
-.B \-ff
-is used.
-If the argument begins with `|' or with `!' then the rest of the
-argument is treated as a command and all output is piped to it.
-This is convenient for piping the debugging output to a program
-without affecting the redirections of executed programs.
+where pid is the numeric process id of each process.
+This is incompatible with
+.BR \-c ,
+since no per-process counts are kept.
+.TP
+.BI "\-I " interruptible
+When strace can be interrupted by signals (such as pressing ^C).
+1: no signals are blocked; 2: fatal signals are blocked while decoding syscall
+(default); 3: fatal signals are always blocked (default if '-o FILE PROG');
+4: fatal signals and SIGTSTP (^Z) are always blocked (useful to make
+strace -o FILE PROG not stop on ^Z).
+.SS Startup
+.TP 12
.TP
-.BI "\-O " overhead
-Set the overhead for tracing system calls to
-.I overhead
-microseconds.
-This is useful for overriding the default heuristic for guessing
-how much time is spent in mere measuring when timing system calls using
-the
-.B \-c
-option. The accuracy of the heuristic can be gauged by timing a given
-program run without tracing (using
-.BR time (1))
-and comparing the accumulated
-system call time to the total produced using
-.BR \-c .
+\fB\-E\ \fIvar\fR=\,\fIval\fR
+Run command with
+.IR var = val
+in its list of environment variables.
+.TP
+.BI "\-E " var
+Remove
+.IR var
+from the inherited list of environment variables before passing it on to
+the command.
.TP
.BI "\-p " pid
Attach to the process with the process
leaving it (them) to continue running.
Multiple
.B \-p
-options can be used to attach to up to 32 processes in addition to
+options can be used to attach to many processes in addition to
.I command
(which is optional if at least one
.B \-p
option is given).
-.TP
-.BI "\-s " strsize
-Specify the maximum string size to print (the default is 32). Note
-that filenames are not considered strings and are always printed in
-full.
-.TP
-.BI "\-S " sortby
-Sort the output of the histogram printed by the
-.B \-c
-option by the specified criterion. Legal values are
-.BR time ,
-.BR calls ,
-.BR name ,
-and
-.B nothing
-(default
-.BR time ).
+.B \-p
+"`pidof PROG`" syntax is supported.
.TP
.BI "\-u " username
Run command with the user \s-1ID\s0, group \s-2ID\s0, and
correct execution of setuid and/or setgid binaries.
Unless this option is used setuid and setgid programs are executed
without effective privileges.
+.SS Miscellaneous
+.TP 12
.TP
-.BI "\-E " var=val
-Run command with
-.IR var=val
-in its list of environment variables.
+.B \-d
+Show some debugging output of
+.B strace
+itself on the standard error.
.TP
-.BI "\-E " var
-Remove
-.IR var
-from the inherited list of environment variables before passing it on to
-the command.
+.B \-F
+This option is now obsolete and it has the same functionality as
+.BR \-f .
+.TP
+.B \-h
+Print the help summary.
+.TP
+.B \-V
+Print the version number of
+.BR strace .
+.SH DIAGNOSTICS
+When
+.I command
+exits,
+.B strace
+exits with the same exit status.
+If
+.I command
+is terminated by a signal,
+.B strace
+terminates itself with the same signal, so that
+.B strace
+can be used as a wrapper process transparent to the invoking parent process.
+Note that parent-child relationship (signal stop notifications,
+getppid() value, etc) between traced process and its parent are not preserved
+unless
+.B \-D
+is used.
+.LP
+When using
+.B \-p
+without a
+.IR command ,
+the exit status of
+.B strace
+is zero unless no processes has been attached or there was an unexpected error
+in doing the tracing.
.SH "SETUID INSTALLATION"
If
.B strace
to those users who have this trust.
For example, it makes sense to install a special version of
.B strace
-with mode `rwsr-xr--', user
+with mode 'rwsr-xr--', user
.B root
and group
.BR trace ,
a non-setuid version of
.B strace
for ordinary lusers to use.
-.SH "SEE ALSO"
-.BR ptrace (2),
-.BR proc (4),
-.BR time (1),
-.BR trace (1),
-.BR truss (1)
.SH NOTES
It is a pity that so much tracing clutter is produced by systems
employing shared libraries.
system call interface and are accounted for by C library wrapper
functions.
.LP
-On some platforms a process that has a system call trace applied
-to it with the
+Some system calls have different names in different architectures and
+personalities. In these cases, system call filtering and printing
+uses the names that match corresponding
+.BR __NR_ *
+kernel macros of the tracee's architecture and personality.
+There are two exceptions from this general rule:
+.BR arm_fadvise64_64 (2)
+ARM syscall and
+.BR xtensa_fadvise64_64 (2)
+Xtensa syscall are filtered and printed as
+.BR fadvise64_64 (2).
+.LP
+On some platforms a process that is attached to with the
.B \-p
-option will receive a
-.BR \s-1SIGSTOP\s0 .
-This signal may interrupt a system call that is not restartable.
+option may observe a spurious EINTR return from the current
+system call that is not restartable. (Ideally, all system calls
+should be restarted on strace attach, making the attach invisible
+to the traced process, but a few system calls aren't.
+Arguably, every instance of such behavior is a kernel bug.)
This may have an unpredictable effect on the process
if the process takes no action to restart the system call.
.SH BUGS
.SM ID
privileges while being traced.
.LP
-A traced process ignores
-.SM SIGSTOP
-except on SVR4 platforms.
-.LP
-A traced process which tries to block SIGTRAP will be sent a SIGSTOP
-in an attempt to force continuation of tracing.
-.LP
A traced process runs slowly.
.LP
Traced processes which are descended from
may be left running after an interrupt signal (\c
.SM CTRL\s0-C).
.LP
-On Linux, exciting as it would be, tracing the init process is forbidden.
-.LP
The
.B \-i
option is weakly supported.
.SH HISTORY
-.B strace
The original
.B strace
was written by Paul Kranenburg
.B strace
to Irix
and tired of writing about himself in the third person.
-.SH PROBLEMS
+.SH REPORTING BUGS
Problems with
.B strace
-should be reported via the Debian Bug Tracking System,
-or to the
+should be reported to the
.B strace
-mailing list at <strace-devel@lists.sourceforge.net>.
+mailing list at <strace\-devel@lists.sourceforge.net>.
+.SH "SEE ALSO"
+.BR ltrace (1),
+.BR time (1),
+.BR ptrace (2),
+.BR proc (5)
projects / strace / blobdiff