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ltrace is a debugging utility in Linux, used to display the calls a userspace application makes to shared libraries.

Overview

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It does this by hooking into the dynamic loading system, allowing it to insert shims which display the parameters which the applications uses when making the call, and the return value which the library call reports. ltrace can also trace Linux system calls. Because it uses the dynamic library hooking mechanism, ltrace cannot trace calls to libraries which are statically linked directly to the target binary. Since 0.7.3, ltrace can also trace calls to libraries which are loaded using dlopen.

Example output

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The following is the first few lines of an invocation of xterm. It shows ltrace displaying calls to a variety of libraries, including the C standard library (malloc, strlen), POSIX libraries (getuid), X Toolkit Intrinsics (XtOpenApplication), and the X11 inter-client communication library (IceAddConnectionWatch). A call's return value is shown after the = symbol. 

[pid 11783] __libc_start_main(0x407420, 1, 0x7fff75b6aad8, 0x443cc0, 0x443d50 <unfinished ...>
[pid 11783] geteuid()                            = 1000
[pid 11783] getegid()                            = 1000
[pid 11783] getuid()                             = 1000
[pid 11783] getgid()                             = 1000
[pid 11783] setuid(1000)                         = 0
[pid 11783] malloc(91)                           = 0x00cf8010
[pid 11783] XtSetLanguageProc(0, 0, 0, 0x7f968c9a3740, 1) = 0x7f968bc16220
[pid 11783] ioctl(0, 21505, 0x7fff75b6a960)      = 0
[pid 11783] XtSetErrorHandler(0x42bbb0, 0x44f99c, 0x669f80, 146, 0x7fff75b6a72c) = 0
[pid 11783] XtOpenApplication(0x670260, 0x44f99c, 0x669f80, 146, 0x7fff75b6a72c) = 0xd219a0
[pid 11783] IceAddConnectionWatch(0x42adc0, 0, 0, 0x7f968c9a3748, 0 <unfinished ...>
[pid 11783] IceConnectionNumber(0xd17ec0, 0, 1, 0xcfb138, 0xd17c00) = 4
[pid 11783] <... IceAddConnectionWatch resumed> ) = 1
[pid 11783] XtSetErrorHandler(0, 0, 1, 0xcfb138, 0xd17c00) = 0
[pid 11783] XtGetApplicationResources(0xd219a0, 0x6701c0, 0x66b220, 34, 0) = 0
[pid 11783] strlen("off")                        = 3

See also

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  • strace – system call tracer for linux
  • ktrace – system call tracer for *BSD
  • DTrace – Solaris / OS X / BSD / Windows kernel tracing tool
  • SystemTap – Linux kernel tracing tool

References

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📚 Artikel Terkait di Wikipedia

DTrace

ktrace – a BSD Unix and macOS utility that traces kernel–program interactions ltrace – a Linux debugging utility, displays the calls a userland application makes

Ftrace

a BSD Unix and Mac OS X utility that traces kernel–program interactions ltrace – a Linux debugging utility, displays the calls a userland application makes

Ptrace

used by debuggers (such as gdb and dbx), by tracing tools like strace and ltrace, and by code coverage tools. ptrace is also used by specialized programs

Strace

different feature sets or results. Such tools include the following: Linux has ltrace that can trace library and system calls, xtrace that can trace X Window

List of C software and tools

debugger strace — diagnostic, debugging, and instructional userspace utility. ltrace — debugger and library call tracing tool Cantata++ — commercial unit and