ltrace <root
LTRACE(1)                                 User Commands                                 LTRACE(1)

NAME
       ltrace - A library call tracer

SYNOPSIS
       ltrace  [-e  filter|-L]  [-l|--library=library_pattern] [-x filter] [-S] [-b|--no-signals]
       [-i] [-w|--where=nr]  [-r|-t|-tt|-ttt]  [-T]  [-F  filename]  [-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 -V|--version

       ltrace -h|--help

DESCRIPTION
       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 executed by the program.

       Its use is very similar to strace(1).

OPTIONS
       -a, --align column
              Align return values in a specific column (default column is 5/8 of screen width).

       -A maxelts
              Maximum number of array elements to print  before  suppressing  the  rest  with  an
              ellipsis ("...").  This also limits number of recursive structure expansions.

       -b, --no-signals
              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.

       -C, --demangle
              Decode  (demangle)  low-level symbol names into user-level names.  Besides removing
              any initial underscore prefix used by the system, 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.

       -e filter
              A qualifying expression which modifies which library calls to trace.  The format of
              the filter expression is described in the section FILTER EXPRESSIONS.  If more than
              one -e option appears on the command line, the library calls that match any of them
              are traced.  If no -e is given, @MAIN is assumed as a default.

       -f     Trace child processes as they are created by currently traced processes as a result
              of the fork(2) or clone(2) system calls.  The new process is attached immediately.

       -F filename
              Load  an  alternate config file. Normally, /etc/ltrace.conf and ~/.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.

       -h, --help
              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_pat‐
              tern.   Multiple  library  patters  can be specified 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 simply dependency ordering.  If you  want  to  make  sure
              that symbols in given library are actually called, use -x @library_pattern instead.

       -L     When no -e option is given, don't assume the default action of @MAIN.

       -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 C++ runtime.

       -o, --output filename
              Write the trace output to the file filename rather than to stderr.

       -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 execute.  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 dif‐
              ference between the beginning of successive lines.

       -s strsize
              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.

       -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.

       -T     Show  the  time  spent inside each call. This records the time  difference  between
              the beginning and the end of each call.

       -u username
              Run  command  with  the userid, groupid 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.

       -w, --where nr
              Show  backtrace  of  nr  stack frames for each traced function. This option enabled
              only if libunwind support was enabled at compile time.

       -x filter
              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 given.

       -V, --version
              Show the version number of ltrace and exit.

FILTER EXPRESSIONS
       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 exam‐
       ple, the following would trace calls to malloc and free, except those done by libc:

       -e malloc+free-@libc.so*

       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][@library_pattern]}

       Symbol_pattern is used to match symbol names, library_pattern to  match  library  SONAMEs.
       Both  are  implicitly globs, but can be regular expressions as well (see below).  The glob
       syntax supports meta-characters * and ? and character classes,  similarly  to  what  basic
       bash  globs support.  ^ and $ are recognized to mean, respectively, start and end of given
       name.

       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 excep‐
       tion 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  con‐
       sidered a regular expression instead.  As a shorthand, instead of writing /x/@/y/, you can
       write /x@y/.

       If the library pattern starts with a slash, it is not a  SONAME  expression,  but  a  path
       expression, and is matched against the library path name.

       The  first  rule  may lack a sign, in which case + is assumed.  If, on the other hand, the
       first rule has a - sign, it is as if there was another rule @ in front of  it,  which  has
       the effect of tracing complement of given rule.

       The above rules are used to construct the set of traced symbols.  Each candidate symbol is
       passed through the chain of above rules.   Initially,  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.

BUGS
       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  (ltrace-
       devel@lists.alioth.debian.org),  or  use  the  reportbug(1)  program  if you are under the
       Debian GNU/Linux distribution.

FILES
       /etc/ltrace.conf
              System configuration file

       ~/.ltrace.conf
              Personal config file, overrides /etc/ltrace.conf

AUTHOR
       Juan Cespedes 
       Petr Machata 

SEE ALSO
       ltrace.conf(5), strace(1), ptrace(2)

                                           January 2013                                 LTRACE(1)

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