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  uClibc - a Small C Library for Linux

  Erik Andersen 

uClibc (aka µClibc/pronounced yew-see-lib-see) is a C library for

developing embedded Linux systems. It is much smaller than the

GNU C Library, but nearly all applications supported by glibc

also work perfectly with uClibc. Porting applications from glibc

to uClibc typically involves just recompiling the source code.

uClibc even supports shared libraries and threading. It currently

runs on standard Linux and MMU-less (also known as µClinux)

systems with support for alpha, ARM, cris, e1, h8300, i386, i960,

m68k, microblaze, mips/mipsel, PowerPC, SH, SPARC, and v850

processors.

If you are building an embedded Linux system and you find that

glibc is eating up too much space, you should consider using

uClibc.  If you are building a huge fileserver with 12 Terabytes

of storage, then using glibc may make more sense.  Unless, for

example, that 12 Terabytes will be Network Attached Storage and

you plan to burn Linux into the system's firmware...

uClibc is maintained by Erik Andersen and is licensed under the

GNU LIBRARY GENERAL PUBLIC LICENSE . This license allows you to

make closed source commercial applications using an unmodified

version of uClibc (Please consider sharing some of the money you

make ;-). You do not need to give away all your source code just

because you use uClibc and/or run on Linux.  You should, however,

carefuly review the license and make certain you understand and

abide by it strictly.

For installation instructions, see the file INSTALL.

uClibc strives to be standards compliant, which means that most

documentation written for SuSv3, or for glibc also applies to

uClibc functions.  However, many GNU extensions are not supported

because they have not been ported, or more importantly, would

increase the size of uClibc disproportional to the added

functionality.  There is some discussion of these differences

in the "docs" directory.

Additional information (recent releases, FAQ, mailing list, bugs,

etc.) can be found at http://www.uclibc.org/.

uClibc may be freely modified and distributed under the terms of

the GNU Library General Public License, which can be found in the

file COPYING.LIB.

Please Note:

        There is an unwholesomely huge amount of code out there

        that depends on the presence of GNU libc header files.

        We have GNU libc compatible header files.  So we have

        committed a horrible sin in uClibc.  We _lie_ and claim

        to be GNU libc in order to force these applications to

        work as their developers intended.  This is IMHO,

        pardonable, since these defines are not really intended

        to check for the presence of a particular library, but

        rather are used to define an _interface_.  Some programs

        are especially chummy with glibc, and may need this

        behavior disabled by adding CFLAGS+=-D__FORCE_NOGLIBC

        If you want to make special exceptions in your code which are

        specifically for uClibc, you can make certain to include features.h,

        and then have your code check for uClibc as follows:

            #ifdef __UCLIBC__

                    do_something_special();

            #endif

And most of all, but sure to have some fun!

 -Erik