strace [ -CdffhiqrtttTvxx ] [ -acolumn ] [ -eexpr ] ... [ -ofile ] [ -ppid ] ... [ -sstrsize ] [
-uusername ] [ -Evar=val ] ... [ -Evar ] ... [ command [ arg ... ] ]
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-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 -c is used with -f or -F (below), only
aggregate totals for all traced processes are kept.
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-C Like -c but also print regular output while processes are running.
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-d Show some debugging output of strace itself on the standard error.
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-f Trace child processes as they are created by currently traced processes as a result of
the fork(2) system call.
On non-Linux platforms the new process is attached to as soon as its pid is known
(through the return value of fork(2) in the parent process). This means that such
children may run uncontrolled for a while (especially in the case of a vfork(2)),
until the parent is scheduled again to complete its (v)fork(2) call. On Linux the
child is traced from its first instruction with no delay. If the parent process
decides to 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).
On SunOS 4.x the tracing of vforks is accomplished with some dynamic linking trickery.
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-ff If the -o filename option is in effect, each processes trace is written to
filename.pid where pid is the numeric process id of each process. This is
incompatible with -c, since no per-process counts are kept.
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-F This option is now obsolete and it has the same functionality as -f.
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-h Print the help summary.
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-i Print the instruction pointer at the time of the system call.
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-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.
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-r Print a relative timestamp upon entry to each system call. This records the time
difference between the beginning of successive system calls.
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-t Prefix each line of the trace with the time of day.
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-tt If given twice, the time printed will include the microseconds.
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-ttt If given thrice, the time printed will include the microseconds and the leading
portion will be printed as the number of seconds since the epoch.
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-T Show the time spent in system calls. This records the time difference between the
beginning and the end of each system call.
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-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.
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-V Print the version number of strace.
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-x Print all non-ASCII strings in hexadecimal string format.
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-xx Print all strings in hexadecimal string format.
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-a column Align return values in a specific column (default column 40).
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-e expr A qualifying expression which modifies which events to trace or how to trace them.
The format of the expression is:
[qualifier=][!]value1[,value2]...
where qualifier is one of trace, abbrev, verbose, raw, signal, read, or write and
value is a qualifier-dependent symbol or number. The default qualifier is trace.
Using an exclamation mark negates the set of values. For example, -e open means
literally -e trace=open which in turn means trace only the open system call. By
contrast, -e trace=!open means to trace every system call except open. In addition,
the special values all and none have the obvious meanings.
Note that some shells use the exclamation point for history expansion even inside
quoted arguments. If so, you must escape the exclamation point with a backslash.
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-e trace=set
Trace only the specified set of system calls. The -c option is useful for determining
which system calls might be useful to trace. For example, 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 trace=all.
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-e trace=file
Trace all system calls which take a file name as an argument. You can think of this
as an abbreviation for -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 lstat in the list.
Betchya woulda forgot that one.
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-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.
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-e trace=network
Trace all the network related system calls.
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-e trace=signal
Trace all signal related system calls.
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-e trace=ipc
Trace all IPC related system calls.
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-e trace=desc
Trace all file descriptor related system calls.
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-e abbrev=set
Abbreviate the output from printing each member of large structures. The default is
abbrev=all. The -v option has the effect of abbrev=none.
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-e verbose=set
Dereference structures for the specified set of system calls. The default is
verbose=all.
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-e raw=set 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.
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-e signal=set
Trace only the specified subset of signals. The default is signal=all. For example,
signal =! SIGIO (or signal=!io) causes SIGIO signals not to be traced.
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-e read=set 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 -e read=3,5. Note that this is independent from the normal
tracing of the read(2) system call which is controlled by the option -e trace=read.
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-e write=set
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 -e write=3,5. Note that this is independent from the normal
tracing of the write(2) system call which is controlled by the option -e trace=write.
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-o filename Write the trace output to the file filename rather than to stderr. Use filename.pid
if -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.
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-O overhead Set the overhead for tracing system calls to 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 -c option. The accuracy of the heuristic
can be gauged by timing a given program run without tracing (using time(1)) and
comparing the accumulated system call time to the total produced using -c.
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-p pid Attach to the process with the process ID pid and begin tracing. The trace may be
terminated at any time by a keyboard interrupt signal (CTRL-C). strace will respond
by detaching itself from the traced process(es) leaving it (them) to continue running.
Multiple -p options can be used to attach to up to 32 processes in addition to command
(which is optional if at least one -p option is given).
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-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.
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-S sortby Sort the output of the histogram printed by the -c option by the specified criterion.
Legal values are time, calls, name, and nothing (default is time).
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-u username Run command with the user ID, group ID, and supplementary groups of username. This
option is only useful when running as root and enables the correct execution of setuid
and/or setgid binaries. Unless this option is used setuid and setgid programs are
executed without effective privileges.
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-E var=val Run command with var=val in its list of environment variables.
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-E var Remove var from the inherited list of environment variables before passing it on to
the command.
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