.\" -*-nroff-*-
-.\" Copyright (c) 2012 Petr Machata, Red Hat Inc.
+.\" Copyright (c) 2012, 2013, 2014 Petr Machata, Red Hat Inc.
.\" Copyright (c) 1997-2005 Juan Cespedes <cespedes@debian.org>
.\"
.\" This program is free software; you can redistribute it and/or
.\" Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
.\" 02110-1301 USA
.\"
-.TH LTRACE "1" "October 2012" "" "User Commands"
+.TH LTRACE "1" "January 2013" "" "User Commands"
.SH NAME
ltrace \- A library call tracer
.SH SYNOPSIS
+.\"
+.\" ---------------------------------------------------------------------------
+.\"
+.PP
.B ltrace
-.I "[-bCfghiLrStttV] [-a column] [-A maxelts] [-D level] [-e expr] [-l library_pattern] [-n nr] [-o filename] [-p pid] ... [-s strsize] [-u username] [-w count] [-x extern] ... [--align=column] [--debug=level] [--demangle] [--help] [--indent=nr] [--library=library_pattern] [--no-signals] [--output=filename] [--version] [--where=NR] [command [arg ...]]"
+.\"
+.\" What events to trace:
+.\"
+[\-e \fIfilter\fR|\-L] [\-l|\-\-library=\fIlibrary_pattern\fR]
+[\-x \fIfilter\fR] [\-S] [\-b|\-\-no-signals]
+.\"
+.\" What to display with each event:
+.\"
+[\-i] [\-w|\-\-where=\fInr\fR] [\-r|\-t|\-tt|\-ttt] [\-T]
+.\"
+.\" Output formatting:
+.\"
+[[\-F|\-\-config] \fIpathlist\fR]
+[\-A \fImaxelts\fR] [\-s \fIstrsize\fR] [\-C|\-\-demangle]
+[\-a|\-\-align \fIcolumn\fR] [\-n|\-\-indent \fInr\fR]
+[\-o|\-\-output \fIfilename\fR]
+.\"
+.\" Various:
+.\"
+[\-D|\-\-debug \fImask\fR] [\-u \fIusername\fR]
+.\"
+.\" What processes to trace:
+.\"
+[\-f] [\-p \fIpid\fR] [[\-\-] \fIcommand [arg ...]\fR]
+.\"
+.\" ---------------------------------------------------------------------------
+.\"
+.PP
+.BR ltrace " \-c"
+.\"
+.\" What events to trace:
+.\"
+[\-e \fIfilter\fR|\-L] [\-l|\-\-library=\fIlibrary_pattern\fR]
+[\-x \fIfilter\fR] [\-S]
+.\"
+.\" Output formatting:
+.\"
+[\-o|\-\-output \fIfilename\fR]
+.\"
+.\" What processes to trace:
+.\"
+[\-f] [\-p \fIpid\fR] [[\-\-] \fIcommand [arg ...]\fR]
+.\"
+.\" ---------------------------------------------------------------------------
+.\"
+.PP
+.BR ltrace " \-V|\-\-version"
+.PP
+.BR ltrace " \-h|\-\-help"
.SH DESCRIPTION
.B ltrace
Its use is very similar to
.BR strace(1) .
+.B ltrace
+shows parameters of invoked functions and system calls. To determine
+what arguments each function has, it needs external declaration of
+function prototypes. Those are stored in files called \fIprototype
+libraries\fR--see ltrace.conf(5) for details on the syntax of these
+files. See the section \fBPROTOTYPE LIBRARY DISCOVERY\fR to learn how
+\fBltrace\fR finds prototype libraries.
+
.SH OPTIONS
-.TP
-.I \-a, \-\-align column
+.PP
+.IP "\-a, \-\-align \fIcolumn"
Align return values in a specific
.IR column
(default column is 5/8 of screen width).
-.TP
-.I \-A maxelts
+.IP "\-A \fImaxelts"
Maximum number of array elements to print before suppressing the rest
with an ellipsis ("..."). This also limits number of recursive
structure expansions.
-.TP
-.I \-b, \-\-no-signals
-Disable printing of signals recieved by the traced process.
-.TP
-.I \-c
-Count time and calls for each library call and report a summary on program exit.
-.TP
-.I \-C, \-\-demangle
+.IP "\-b, \-\-no-signals"
+Disable printing of signals received by the traced process.
+.IP \-c
+Count time and calls for each library call and report a summary on
+program exit.
+.IP "\-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.
-.TP
-.I \-D, \-\-debug level
-Show debugging output of
-.B ltrace
-itself.
-.I level
-must be a sum of some of the following numbers:
-.RS
-.TP
-.B 01
-DEBUG_GENERAL. Shows helpful progress information
-.TP
-.B 010
-DEBUG_EVENT. Shows every event received by a traced program
-.TP
-.B 020
-DEBUG_PROCESS. Shows every action
-.B ltrace
-carries upon a traced process
-.TP
-.B 040
-DEBUG_FUNCTION. Shows every entry to internal functions
-.RE
-.TP
-.I \-e filter
+.IP "\-D, \-\-debug \fRmask\fI"
+Show debugging output of \fBltrace\fR itself. \fImask\fR is a number
+describing which debug messages should be displayed. Use the option
+\-Dh to see what can be used, but note that currently the only
+reliable debugmask is 77, which shows all debug messages.
+.IP "\-e \fIfilter"
A qualifying expression which modifies which library calls to trace.
The format of the filter expression is described in the section
\fBFILTER EXPRESSIONS\fR. 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, \fB@MAIN\fR is assumed as a default.
-.TP
-.I \-f
+.IP \-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.
-.TP
-.I \-F
-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.
-.TP
-.I \-h, \-\-help
+.IP "\-F, \-\-config \fIpathlist"
+Contains a colon-separated list of paths. If a path refers to a
+directory, that directory is considered when prototype libraries are
+searched (see the section \fBPROTOTYPE LIBRARY DISCOVERY\fR). If it refers to
+a file, that file is imported implicitly to all loaded prototype
+libraries.
+.IP "\-h, \-\-help"
Show a summary of the options to ltrace and exit.
-.TP
-.I \-i
+.IP \-i
Print the instruction pointer at the time of the library call.
-.TP
-.I \-l, \-\-library library_pattern
+.IP "\-l, \-\-library \fIlibrary_pattern"
Display only calls to functions implemented by libraries that match
.I library_pattern.
Multiple library patters can be specified with several instances of
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 \fB-x @\fIlibrary_pattern\fR instead.
-.TP
-.I \-L
-When no -e option is given, don't assume the default action of
-\fB@MAIN\fR.
-.TP
-.I \-n, \-\-indent nr
-Indent trace output by
-.I nr
-number of spaces for each new nested call. Using this option makes
-the program flow visualization easy to follow.
-.TP
-.I \-o, \-\-output filename
-Write the trace output to the file
-.I filename
-rather than to stderr.
-.TP
-.I \-p pid
-Attach to the process with the process ID
-.I pid
-and begin tracing.
-.TP
-.I \-r
-Print a relative timestamp with each line of the trace.
-This records the time difference between the beginning of
-successive lines.
-.TP
-.I \-s strsize
+.IP \-L
+When no \-e option is given, don't assume the default action of
+\fB@MAIN\fR. In practice this means that library calls will not be
+traced.
+.IP "\-n, \-\-indent \fInr"
+Indent trace output by \fInr\fR 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.
+.IP "\-o, \-\-output \fIfilename"
+Write the trace output to the file \fIfilename\fR rather than to
+stderr.
+.IP "\-p \fIpid"
+Attach to the process with the process ID \fIpid\fR 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.
+.IP \-r
+Print a relative timestamp with each line of the trace. This records
+the time difference between the beginning of successive lines.
+.IP "\-s \fIstrsize"
Specify the maximum string size to print (the default is 32).
-.TP
-.I \-S
+.IP \-S
Display system calls as well as library calls
-.TP
-.I \-t
+.IP \-t
Prefix each line of the trace with the time of day.
-.TP
-.I \-tt
+.IP \-tt
If given twice, the time printed will include the microseconds.
-.TP
-.I \-ttt
+.IP \-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.
-.TP
-.I \-T
+.IP \-T
Show the time spent inside each call. This records the time difference
between the beginning and the end of each call.
-.TP
-.I \-u username
+.IP "\-u \fIusername"
Run command with the userid, groupid and supplementary groups of
.IR username .
This option is only useful when running as root and enables the
correct execution of setuid and/or setgid binaries.
-.TP
-.I \-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.
-.TP
-.I \-x filter
+.IP "\-w, \-\-where \fInr"
+Show backtrace of \fInr\fR stack frames for each traced function. This
+option enabled only if elfutils or libunwind support was enabled at compile
+time.
+.IP "\-x \fIfilter"
A qualifying expression which modifies which symbol table entry points
to trace. The format of the filter expression is described in the
section \fBFILTER EXPRESSIONS\fR. 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.
-.TP
-.I \-V, \-\-version
+.IP "\-V, \-\-version"
Show the version number of ltrace and exit.
.SH FILTER EXPRESSIONS
The first rule may lack a sign, in which case \fB+\fR is assumed. If,
on the other hand, the first rule has a \fB-\fR sign, it is as if
-there was another rule \fB@*\fR in front of it.
+there was another rule \fB@\fR 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.
becomes \fIunmarked\fR again. If, after applying all rules, the
symbol is \fImarked\fR, it will be traced.
+.SH PROTOTYPE LIBRARY DISCOVERY
+
+When a library is mapped into the address space of a traced process,
+ltrace needs to know what the prototypes are of functions that this
+library implements. For purposes of ltrace, prototype really is a bit
+more than just type signature: it's also formatting of individual
+parameters and of return value. These prototypes are stored in files
+called prototype libraries.
+
+After a library is mapped, ltrace finds out what its SONAME is. It
+then looks for a file named SONAME.conf--e.g. protolib for libc.so.6
+would be in a file called libc.so.6.conf. When such file is found
+(more about where ltrace looks for these files is below), ltrace reads
+all prototypes stored therein. When a symbol table entry point (such
+as those traced by \-x) is hit, the prototype is looked up in a
+prototype library corresponding to the library where the hit occurred.
+When a library call (such as those traced by \-e and \-l) is hit, the
+prototype is looked up in all prototype libraries loaded for given
+process. That is necessary, because a library call is traced in a PLT
+table of a caller library, but the prototype is described at callee
+library.
+
+If a library has no SONAME, basename of library file is considered
+instead. For the main program binary, basename is considered as well
+(e.g. protolib for /bin/echo would be called echo.conf). If a name
+corresponding to soname (e.g. libc.so.6.conf) is not found, and the
+module under consideration is a shared library, ltrace also tries
+partial matches. Ltrace snips one period after another, retrying the
+search, until either a protolib is found, or X.so is all that's left.
+Thus libc.so.conf would be considered, but libc.conf not.
+
+When looking for a prototype library, ltrace potentially looks into
+several directories. On Linux, those are $XDG_CONFIG_HOME/ltrace,
+$HOME/.ltrace, \fIX\fR/ltrace for each \fIX\fR in $XDG_CONFIG_DIRS and
+/usr/share/ltrace. If the environment variable XDG_CONFIG_HOME is not
+defined, ltrace looks into $HOME/.config/ltrace instead.
+
+There's also a mechanism for loading legacy config files. If
+$HOME/.ltrace.conf exists it is imported to every loaded prototype
+library. Similarly for /etc/ltrace.conf. If both exist, both are
+imported, and $HOME/.ltrace.conf is consulted before /etc/ltrace.conf.
+
+If \-F contains any directories, those are searched in precedence to
+the above system directories, in the same order in which they are
+mentioned in \-F. Any files passed in \-F are imported similarly to
+above legacy config files, before them.
+
+See ltrace.conf(5) for details on the syntax of ltrace prototype
+library files.
+
.SH BUGS
It has most of the bugs stated in
.BR strace(1) .
.LP
-It only works on Linux and in a small subset of architectures.
+It only works on Linux and in some architectures.
.LP
.PP
If you would like to report a bug, send a message to the mailing list
projects / platform / upstream / ltrace.git / blobdiff