ltrace [-e filter|-L] [-l|--library=library_pattern] [-x filter] [-S]
[-b|--no-signals] [-i] [-w|--where=nr] [-r|-t|-tt|-ttt] [-T] [-F file-
name] [-A maxelts] [-s strsize] [-C|--demangle] [-a|--align column]
[-n|--indent nr] [-o|--output filename] [-D|--debug mask] [-u username]
[-f] [-p pid] [[--] command [arg ...]]
ltrace -c [-e filter|-L] [-l|--library=library_pattern] [-x filter]
[-S] [-o|--output filename] [-f] [-p pid] [[--] command [arg ...]]
ltrace is a program that simply runs the specified command until it
exits. It intercepts and records the dynamic library calls which are
called by the executed process and the signals which are received by
that process. It can also intercept and print the system calls exe-
cuted by the program.
Its use is very similar to strace(1).
-a, --align column
Align return values in a specific column (default column is 5/8
of screen width).
Maximum number of array elements to print before suppressing the
rest with an ellipsis ("..."). This also limits number of
recursive structure expansions.
Disable printing of signals recieved by the traced process.
-c Count time and calls for each library call and report a summary
on program exit.
Decode (demangle) low-level symbol names into user-level names.
Besides removing any initial underscore prefix used by the sys-
tem, this makes C++ function names readable.
-D, --debug mask
Show debugging output of ltrace itself. mask is a number with
internal meaning that's not really well defined at all. mask of
77 shows all debug messages, which is what you usually need.
~/.ltrace.conf will be read (the latter only if it exists). Use
this option to load the given file or files instead of those two
default files. See ltrace.conf(5) for details on the syntax of
ltrace configuration files.
Show a summary of the options to ltrace and exit.
-i Print the instruction pointer at the time of the library call.
-l, --library library_pattern
Display only calls to functions implemented by libraries that
match library_pattern. Multiple library patters can be speci-
fied with several instances of this option. Syntax of
library_pattern is described in section FILTER EXPRESSIONS.
Note that while this option selects calls that might be directed
to the selected libraries, there's no actual guarantee that the
call won't be directed elsewhere due to e.g. LD_PRELOAD or sim-
ply dependency ordering. If you want to make sure that symbols
in given library are actually called, use -x @library_pattern
-L When no -e option is given, don't assume the default action of
-n, --indent nr
Indent trace output by nr spaces for each level of call nesting.
Using this option makes the program flow visualization easy to
follow. This indents uselessly also functions that never
return, such as service functions for throwing exceptions in the
-o, --output filename
Write the trace output to the file filename rather than to
-p pid Attach to the process with the process ID pid and begin tracing.
This option can be used together with passing a command to exe-
cute. It is possible to attach to several processes by passing
more than one option -p.
-r Print a relative timestamp with each line of the trace. This
records the time difference between the beginning of successive
Specify the maximum string size to print (the default is 32).
-S Display system calls as well as library calls
-t Prefix each line of the trace with the time of day.
-tt If given twice, the time printed will include the microseconds.
-w, --where nr
Show backtrace of nr stack frames for each traced function. This
option enabled only if libunwind support was enabled at compile
A qualifying expression which modifies which symbol table entry
points to trace. The format of the filter expression is
described in the section FILTER EXPRESSIONS. If more than one
-x option appears on the command line, the symbols that match
any of them are traced. No entry points are traced if no -x is
Show the version number of ltrace and exit.
Filter expression is a chain of glob- or regexp-based rules that are
used to pick symbols for tracing from libraries that the process uses.
Most of it is intuitive, so as an example, the following would trace
calls to malloc and free, except those done by libc:
This reads: trace malloc and free, but don't trace anything that comes
from libc. Semi-formally, the syntax of the above example looks
approximately like this:
Symbol_pattern is used to match symbol names, library_pattern to match
library SONAMEs. Both are implicitly globs, but can be regular expres-
sions as well (see below). The glob syntax supports meta-characters *
and ? and character classes, similarly to what basic bash globs sup-
port. ^ and $ are recognized to mean, respectively, start and end of
Both symbol_pattern and library_pattern have to match the whole name.
If you want to match only part of the name, surround it with one or two
*'s as appropriate. The exception is if the pattern is not mentioned
at all, in which case it's as if the corresponding pattern were *. (So
malloc is really malloc@* and @libc.* is really *@libc.*.)
In libraries that don't have an explicit SONAME, basename is taken for
SONAME. That holds for main binary as well: /bin/echo has an implicit
SONAME of echo. In addition to that, special library pattern MAIN
always matches symbols in the main binary and never a library with
actual SONAME MAIN (use e.g. ^MAIN or [M]AIN for that).
If the symbol or library pattern is surrounded in slashes (/like
this/), then it is considered a regular expression instead. As a
shorthand, instead of writing /x/@/y/, you can write /x@y/.
tially, the symbol is unmarked. If it matches a + rule, it becomes
marked, if it matches a - rule, it becomes unmarked again. If, after
applying all rules, the symbol is marked, it will be traced.
It has most of the bugs stated in strace(1).
It only works on Linux and in a small subset of architectures.
If you would like to report a bug, send a message to the mailing list
(firstname.lastname@example.org), or use the reportbug(1) program
if you are under the Debian GNU/Linux distribution.
System configuration file
Personal config file, overrides /etc/ltrace.conf
Juan Cespedes <email@example.com>
Petr Machata <firstname.lastname@example.org>
ltrace.conf(5), strace(1), ptrace(2)
January 2013 LTRACE(1)
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