[thirdparty/man-pages.git] / man1 / ldd.1

.\" Copyright 1995-2000 David Engel (david@ods.com)
.\" Copyright 1995 Rickard E. Faith (faith@cs.unc.edu)
.\" Copyright 2000 Ben Collins (bcollins@debian.org)
.\"    Redone for GLibc 2.2
.\" Copyright 2000 Jakub Jelinek (jakub@redhat.com)
.\"    Corrected.
.\" Most of this was copied from the README file.
.\"
.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" Do not restrict distribution.
.\" May be distributed under the GNU General Public License
.\" %%%LICENSE_END
.\"
.TH LDD 1 2015-08-08 "" "Linux Programmer's Manual"
.SH NAME
ldd \- print shared object dependencies
.SH SYNOPSIS
.BR ldd " [\fIoption\fP]... \fIfile\fP..."
.SH DESCRIPTION
.B ldd
prints the shared objects (shared libraries) required by each program or
shared object specified on the command line.
An example of its use and output is the following:

.nf

$ \fBldd /bin/ls\fP
        linux-vdso.so.1 (0x00007ffcc3563000)
        libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000)
        libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000)
        libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000)
        libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000)
        /lib64/ld-linux-x86-64.so.2 (0x00005574bf12e000)
        libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000)
.fi

In the usual case,
.B ldd
invokes the standard dynamic linker (see
.BR ld.so (8))
with the
.B LD_TRACE_LOADED_OBJECTS
environment variable set to 1.
This causes the dynamic linker to inspect the program's dynamic dependencies,
and find (according to the rules described in
.BR ld.so (8))
and load the objects that satisfy those dependencies.
For each dependency,
.BR ldd
displays the location of the matching object
and the (hexadecimal) address at which it is loaded.
(The
.I linux-vdso
and
.I ld-linux
shared dependencies are special; see
.BR vdso (7)
and
.BR ld.so (8).)
.\"
.SS Security
Be aware that in some circumstances, some versions of
.BR ldd
may attempt to obtain the dependency information
by directly executing the program.
.\" Mainline glibc's ldd allows this possibility (the line
.\"      try_trace "$file"
.\" in glibc 2.15, for example), but many distro versions of
.\" ldd seem to remove that code path from the script.
Thus, you should
.I never
employ
.B ldd
on an untrusted executable,
since this may result in the execution of arbitrary code.
A safer alternative when dealing with untrusted executables is:

    $ objdump \-p /path/to/program | grep NEEDED
.SH OPTIONS
.TP
.B \-\-version
Print the version number of
.BR ldd .
.TP
.BR \-v ", " \-\-verbose
Print all information, including, for example,
symbol versioning information.
.TP
.BR \-u ", " \-\-unused
Print unused direct dependencies.
(Since glibc 2.3.4.)
.TP
.BR \-d ", " \-\-data\-relocs
Perform relocations and report any missing objects (ELF only).
.TP
.BR \-r ", " \-\-function\-relocs
Perform relocations for both data objects and functions, and
report any missing objects or functions (ELF only).
.TP
.B \-\-help
Usage information.
.\" .SH NOTES
.\" The standard version of
.\" .B ldd
.\" comes with glibc2.
.\" Libc5 came with an older version, still present
.\" on some systems.
.\" The long options are not supported by the libc5 version.
.\" On the other hand, the glibc2 version does not support
.\" .B \-V
.\" and only has the equivalent
.\" .BR \-\-version .
.\" .LP
.\" The libc5 version of this program will use the name of a library given
.\" on the command line as-is when it contains a \(aq/\(aq; otherwise it
.\" searches for the library in the standard locations.
.\" To run it
.\" on a shared library in the current directory, prefix the name with "./".
.SH BUGS
.B ldd
does not work on a.out shared libraries.
.PP
.B ldd
does not work with some extremely old a.out programs which were
built before
.B ldd
support was added to the compiler releases.
If you use
.B ldd
on one of these programs, the program will attempt to run with
.I argc
= 0 and the results will be unpredictable.
.\" .SH AUTHOR
.\" David Engel.
.\" Roland McGrath and Ulrich Drepper.
.SH SEE ALSO
.BR pldd (1),
.BR sprof (1),
.BR ld.so (8),
.BR ldconfig (8)
Commit	Line	Data
	1	.\" Copyright 1995-2000 David Engel (david@ods.com)
	2	.\" Copyright 1995 Rickard E. Faith (faith@cs.unc.edu)
	3	.\" Copyright 2000 Ben Collins (bcollins@debian.org)
	4	.\" Redone for GLibc 2.2
	5	.\" Copyright 2000 Jakub Jelinek (jakub@redhat.com)
	6	.\" Corrected.
	7	.\" Most of this was copied from the README file.
	8	.\"
	9	.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
	10	.\" Do not restrict distribution.
	11	.\" May be distributed under the GNU General Public License
	12	.\" %%%LICENSE_END
	13	.\"
	14	.TH LDD 1 2015-08-08 "" "Linux Programmer's Manual"
	15	.SH NAME
	16	ldd \- print shared object dependencies
	17	.SH SYNOPSIS
	18	.BR ldd " [\fIoption\fP]... \fIfile\fP..."
	19	.SH DESCRIPTION
	20	.B ldd
	21	prints the shared objects (shared libraries) required by each program or
	22	shared object specified on the command line.
	23	An example of its use and output is the following:
	24
	25	.nf
	26
	27	$ \fBldd /bin/ls\fP
	28	linux-vdso.so.1 (0x00007ffcc3563000)
	29	libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000)
	30	libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000)
	31	libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000)
	32	libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000)
	33	libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000)
	34	/lib64/ld-linux-x86-64.so.2 (0x00005574bf12e000)
	35	libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000)
	36	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000)
	37	.fi
	38
	39	In the usual case,
	40	.B ldd
	41	invokes the standard dynamic linker (see
	42	.BR ld.so (8))
	43	with the
	44	.B LD_TRACE_LOADED_OBJECTS
	45	environment variable set to 1.
	46	This causes the dynamic linker to inspect the program's dynamic dependencies,
	47	and find (according to the rules described in
	48	.BR ld.so (8))
	49	and load the objects that satisfy those dependencies.
	50	For each dependency,
	51	.BR ldd
	52	displays the location of the matching object
	53	and the (hexadecimal) address at which it is loaded.
	54	(The
	55	.I linux-vdso
	56	and
	57	.I ld-linux
	58	shared dependencies are special; see
	59	.BR vdso (7)
	60	and
	61	.BR ld.so (8).)
	62	.\"
	63	.SS Security
	64	Be aware that in some circumstances, some versions of
	65	.BR ldd
	66	may attempt to obtain the dependency information
	67	by directly executing the program.
	68	.\" Mainline glibc's ldd allows this possibility (the line
	69	.\" try_trace "$file"
	70	.\" in glibc 2.15, for example), but many distro versions of
	71	.\" ldd seem to remove that code path from the script.
	72	Thus, you should
	73	.I never
	74	employ
	75	.B ldd
	76	on an untrusted executable,
	77	since this may result in the execution of arbitrary code.
	78	A safer alternative when dealing with untrusted executables is:
	79
	80	$ objdump \-p /path/to/program \| grep NEEDED
	81	.SH OPTIONS
	82	.TP
	83	.B \-\-version
	84	Print the version number of
	85	.BR ldd .
	86	.TP
	87	.BR \-v ", " \-\-verbose
	88	Print all information, including, for example,
	89	symbol versioning information.
	90	.TP
	91	.BR \-u ", " \-\-unused
	92	Print unused direct dependencies.
	93	(Since glibc 2.3.4.)
	94	.TP
	95	.BR \-d ", " \-\-data\-relocs
	96	Perform relocations and report any missing objects (ELF only).
	97	.TP
	98	.BR \-r ", " \-\-function\-relocs
	99	Perform relocations for both data objects and functions, and
	100	report any missing objects or functions (ELF only).
	101	.TP
	102	.B \-\-help
	103	Usage information.
	104	.\" .SH NOTES
	105	.\" The standard version of
	106	.\" .B ldd
	107	.\" comes with glibc2.
	108	.\" Libc5 came with an older version, still present
	109	.\" on some systems.
	110	.\" The long options are not supported by the libc5 version.
	111	.\" On the other hand, the glibc2 version does not support
	112	.\" .B \-V
	113	.\" and only has the equivalent
	114	.\" .BR \-\-version .
	115	.\" .LP
	116	.\" The libc5 version of this program will use the name of a library given
	117	.\" on the command line as-is when it contains a \(aq/\(aq; otherwise it
	118	.\" searches for the library in the standard locations.
	119	.\" To run it
	120	.\" on a shared library in the current directory, prefix the name with "./".
	121	.SH BUGS
	122	.B ldd
	123	does not work on a.out shared libraries.
	124	.PP
	125	.B ldd
	126	does not work with some extremely old a.out programs which were
	127	built before
	128	.B ldd
	129	support was added to the compiler releases.
	130	If you use
	131	.B ldd
	132	on one of these programs, the program will attempt to run with
	133	.I argc
	134	= 0 and the results will be unpredictable.
	135	.\" .SH AUTHOR
	136	.\" David Engel.
	137	.\" Roland McGrath and Ulrich Drepper.
	138	.SH SEE ALSO
	139	.BR pldd (1),
	140	.BR sprof (1),
	141	.BR ld.so (8),
	142	.BR ldconfig (8)