glibc、libc和glib详解 ldd查看依赖动态库

一、什么是glibc、libc和glib

glibc是linux的GUN C函数库，是linux系统中最底层的API，几乎其他任何运行时库都依赖于glibc。glibc除了封装linux操作系统的系统服务，它本身也提供了许多其他必要功能服务的实现，例如：动态加载模块libdl、实时扩展接口librt。

libc是linux的ANSI C函数库，glibc包含libc，一般只包括以下功能：

<ctype.h> <errno.h> <float.h> <math.h> <stddef.h> <stdio.h> <stdlib.h>
<string.h> <time.h> <stdarg.h> <signal.h> <setjmp.h> <locale.h> <assert.h>

1、安装动态库：yum install glibc

2、安装静态库：yum install glibc-static

3、glibc帮助文档：yum install man-pages

4、libc位置：/usr/lib64/libc.so、/usr/lib64/libc.a

5、glib是一个独立的跨平台的C语言工具库；

二、查看glibc版本

[root@ebs-19233 ~]# /lib64/libc.so.6

GNU C Library stable release version 2.12, by Roland McGrath et al.
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.4.7 20120313 (Red Hat 4.4.7-11).
Compiled on a Linux 2.6.32 system on 2015-05-27.
Available extensions:
        The C stubs add-on version 2.1.2.
        crypt add-on version 2.1 by Michael Glad and others
        GNU Libidn by Simon Josefsson
        Native POSIX Threads Library by Ulrich Drepper et al
        BIND-8.2.3-T5B
        RT using linux kernel aio
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
<http://www.gnu.org/software/libc/bugs.html>.

[root@ebs-19233 ~]# strings /lib64/libc.so.6 | grep GLIBC

GLIBC_2.2.5
GLIBC_2.2.6
GLIBC_2.3
GLIBC_2.3.2
GLIBC_2.3.3
GLIBC_2.3.4
GLIBC_2.4
GLIBC_2.5
GLIBC_2.6
GLIBC_2.7
GLIBC_2.8
GLIBC_2.9
GLIBC_2.10
GLIBC_2.11
GLIBC_2.12
GLIBC_PRIVATE

[root@ebs-19233 ~]# ldd  --version

ldd (GNU libc) 2.12
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

三、查看依赖动态库

1、ldd program，会加载依赖库，可以定位缺失依赖库；

2、objdump -p program | grep NEEDED，只能查看直接依赖库；

3、readelf -d program | grep NEEDED，只能查看直接依赖库；

4、ldd可能会执行程序，如果是未知程序，建议使用objdump；

[root@ebs-19233 ~]# ldd /bin/sh
linux-vdso.so.1 =>  (0x00007fffc7361000)
libtinfo.so.5 => /lib64/libtinfo.so.5 (0x0000003207c00000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007fcdec97b000)
libc.so.6 => /lib64/libc.so.6 (0x00007fcdec5e6000)
/lib64/ld-linux-x86-64.so.2 (0x00007fcdecb89000)