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.
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 exclamation
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.
