ltrace(1)ltrace(1)NAMEltrace - A library call tracer
SYNOPSISltrace [-CdfhiLrStttV] [-a column] [-e expr] [-l filename] [-n nr] [-o
filename] [-p pid] ... [-s strsize] [-u username] [-X extern] [-x
extern] ... [--align=column] [--debug] [--demangle] [--help]
[--indent=nr] [--library=filename] [--output=filename] [--version]
[command [arg ...]]
DESCRIPTIONltrace 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).
OPTIONS-a, --align column
Align return values in a specific column (default column is 5/8
of screen width).
-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 prepended by the system,
this makes C++ function names readable.
-d, --debug
Increase the debugging level. Use more (ie. -dd ) for greater
debugging information.
-e expr
A qualifying expression which modifies which events to trace.
The format of the expression is:
[!]value1[,value2]...
where the values are the functions to trace. Using an exclama‐
tion mark negates the set of values. For example -e printf
means to trace only the printf library call. By contrast, -e
!printf means to trace every library call except printf.
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.
-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 as soon as its pid is known.
-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 filename
Display only the symbols included in the library filename. Up
to 20 library names can be specified with several instances of
this option.
-L DON'T display library calls (use it with the -S option).
-n, --indent nr
Indent trace output by nr number of spaces for each new nested
call. Using this option makes the program flow visualization
easy to follow.
-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.
-r Print a relative timestamp with each line of the trace. This
records the time difference 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.
-X extern
Some architectures need to know where to set a breakpoint that
will be hit after the dynamic linker has run. If this flag is
used, then the breakpoint is set at extern, which must be an
external function. By default, '_start' is used. NOTE: this
flag is only available on the architectures that need it.
-x extern
Trace the external function extern. This option may be
repeated.
-V, --version
Show the version number of ltrace and exit.
BUGS
It has most of the bugs stated in strace(1).
Manual page and documentation are not very up-to-date.
Option -f sometimes fails to trace some children.
It only works on Linux and in a small subset of architectures.
Only ELF32 binaries are supported.
Calls to dlopen()ed libraries will not be traced.
If you like to report a bug, send a notice to the author, or use the
reportbug(1) program if you are under the Debian GNU/Linux distribu‐
tion.
FILES
/etc/ltrace.conf
System configuration file
~/.ltrace.conf
Personal config file, overrides /etc/ltrace.conf
AUTHOR
Juan Cespedes <cespedes@debian.org>
SEE ALSOstrace(1), ptrace(2)ltrace(1)
