intro - introduction to the C libraries
cc [flags] file ... [-llibrary]
The manual pages in section 3 provide an overview of the C
library functions,
their error returns, and other common definitions and
concepts.
Most of these functions are available from the C library,
libc. Other
libraries, such as the math library, libm, must be indicated
at compile
time with the -l option of the compiler.
The various libraries (followed by the loader flag):
libbfd (-lbfd)
GNU binary file descriptor library. Allows applications to operate
on object files, regardless of the object file
format. See
`info bfd'.
libc (-lc)
Standard C library functions. When using the C compiler cc(1),
it is not necessary to supply the loader flag -lc
for these functions.
There are several ``libraries'' or groups of
functions
included inside of libc: the standard I/O routines,
database routines,
bit operators, string operators, character
tests and character
operators, DES encryption routines, storage
allocation,
time functions, signal handling, and more.
libcompat (-lcompat)
Functions which are obsolete but are available for
compatibility
with 4.3BSD. In particular, a number of system call
interfaces
provided in previous releases of BSD have been included for
source code compatibility. Use of these routines
should, for the
most part, be avoided. The manual page entry for
each compatibility
routine indicates the proper interface to
use.
libcrypto (-lcrypto)
The OpenSSL crypto library. Implements a range of
cryptographic
algorithms, providing such functionality as symmetric encryption,
public key cryptography, and certificate handling.
See
crypto(3).
libcurses (-lcurses)
libncurses (-lncurses)
libtermcap (-ltermcap)
libtermlib (-ltermlib)
Terminal-independent screen management routines for
two-dimensional
non-bitmap display terminals. This implementation is
``new curses'' and is a replacement for 4.2BSD classic curses.
The libraries libncurses, libtermcap, and libtermlib
are all hard
links to libcurses. This is for compatibility purposes only; new
programs should link with -lcurses. See curses(3)
and
termcap(3).
libcurses++ (-lcurses++)
C++ interface to ncurses routines. See curses(3).
libdes (-ldes)
Implementation of the DES encryption algorithm. See
des_crypt(3).
libedit (-ledit)
Generic line editing and history functions, similar
to those
found in sh(1). Functions using the libedit library
must be
linked with the libcurses library, i.e. -ledit
-lcurses. See
editline(3).
libevent (-levent)
Provides a mechanism to execute a function when a
specific event
on a file descriptor occurs or after a given time
has passed.
See event(3).
libform (-lform)
Terminal-independent facilities for composing form
screens on
character-cell terminals. Functions using the
libform library
must be linked with the libcurses library, i.e.
-lform -lcurses.
See form(3).
libfrtbegin (-lfrtbegin)
libg2c (-lg2c)
Support routines for Fortran functions. These two
libraries were
separated to allow linking Fortran code with other
languages on
ELF platforms. See g77(1).
libgssapi (-lgssapi)
The Generic Security Service Application Program Interface
(GSS-API) provides security services to callers in a
generic
fashion.
libiberty (-liberty)
Collection of subroutines missing in other operating
systems, as
well as the C++ demangler and other functions used
by the GNU
toolchain.
libkadm5clnt (-lkadm5clnt)
Kerberos administration client library, for talking
to a Kerberos
database. Clients communicate via the network.
libkadm5srv (-lkadm5srv)
Kerberos administration server library, for talking
to a Kerberos
database. Servers talk directly to the database.
libkeynote (-lkeynote)
System library for the keynote trust-management system. Trustmanagement
systems provide standard, general-purpose
mechanisms
for specifying application security policies and
credentials.
Functions using the libkeynote library must be
linked with the
libm and libcrypto libraries, i.e. -lkeynote -lm
-lcrypto. See
keynote(3) and keynote(4).
libkrb5 (-lkrb5)
libasn1 (-lasn1)
libcom_err (-lcom_err)
libhdb (-lhdb)
libkafs (-lkafs)
Kerberos 5 libraries. The libraries libasn1,
libcom_err, libhdb,
and libkafs are all hard links to libkrb5. See `info heimdal'.
libkvm (-lkvm)
Kernel memory interface library. Provides a uniform
interface
for accessing kernel virtual memory images, including live systems
and crash dumps. See kvm(3).
libl (-ll)
libfl (-lfl)
The library for lex(1), a lexical analyzer generator. The libfl
library is a hard link to libl.
libm (-lm)
Mathematical functions which comprise the C math library, libm.
See math(3).
libmenu (-lmenu)
Terminal-independent facilities for composing menu
systems on
character-cell terminals. Functions using the
libmenu library
must be linked with the libcurses library, i.e.
-lmenu -lcurses.
See menu(3).
libmilter (-lmilter)
The sendmail(8) mail filter API. See the documentation in
/usr/share/doc/html/milter/.
libmmalloc (-lmmalloc)
GNU memory-mapped malloc package. In this implementation,
mmap(2) is used to obtain memory from the system,
rather than
sbrk(2). See `info mmalloc'.
libobjc (-lobjc)
Library for Objective C, an object-oriented superset
of ANSI C.
Use this to compile Objective C programs.
libocurses (-locurses)
libotermcap (-lotermcap)
Routines to provide the user with a method of updating screens
with reasonable optimisation. The ocurses(3) library is compatible
with the curses library provided in 4.3.
libotermcap is the
4.3-compatible termcap library, and is a hard link
to libocurses.
See otermcap(3).
libopcodes (-lopcodes)
GNU opcode library.
libossaudio (-lossaudio)
Provides an emulation of the OSS (Linux) audio interface. This
is used only for porting programs. See ossaudio(3).
libpanel (-lpanel)
Terminal-independent facilities for stacked windows
on charactercell
terminals. Functions using the libpanel library must be
linked with the libcurses library, i.e. -lpanel
-lcurses. See
panel(3).
libpcap (-lpcap)
Packet capture library. All packets on the network,
even those
destined for other hosts, are accessible through
this library.
See pcap(3).
libperl (-lperl)
Support routines for perl(1).
libpthread (-pthread)
IEEE Std 1003.1-2001 (``POSIX'') threads API and
thread scheduler.
Threaded applications should use -pthread not
-lpthread.
See pthreads(3).
libreadline (-lreadline)
Command line editing interface. See readline(3).
libresolv (-lresolv)
The resolver(3) routines are included in libc. This
is just an
empty library for legacy applications that want to
link with
-lresolv.
librpcsvc (-lrpcsvc)
Generated by rpcgen(1), containing stub functions
for many common
rpc(3) protocols.
libsectok (-lsectok)
Library for communicating with ISO 7816 smartcards.
See
sectok(3).
libskey (-lskey)
Support library for the S/Key one time password
(OTP) authentication
toolkit. See skey(3).
libssl (-lssl)
The OpenSSL ssl library implements the Secure Sockets Layer (SSL
v2/v3) and Transport Layer Security (TLS v1) protocols. See
ssl(3).
libstdc++ (-lstdc++)
GCC subroutine library for C++. See c++(1).
libusbhid (-lusbhid)
Routines to extract data from USB Human Interface
Devices (HIDs).
See usbhid(3).
libutil (-lutil)
System utility functions. These are currently
check_expire(3),
fmt_scaled(3), fparseln(3), getmaxpartitions(3),
getrawpartition(3), login(3), login_fbtab(3), opendev(3),
opendisk(3), openpty(3), pidfile(3), pw_init(3),
pw_lock(3),
readlabelfs(3) and uucplock(3).
libwrap (-lwrap)
TCP wrapper access control library. See hosts_access(3) and
rfc1413(3).
liby (-ly)
The library for yacc(1), an LALR parser generator.
libz (-lz)
General purpose data compression library. The functions in this
library are documented in compress(3). The data
format is described
in RFCs 1950 - 1952.
Platform-specific libraries:
libalpha (-lalpha)
Alpha I/O and memory access functions. See inb(2).
libamd64 (-lamd64)
AMD64 I/O and memory access functions. See
amd64_get_ioperm(2),
amd64_get_ldt(2), amd64_get_mtrr(2), amd64_iopl(2),
and
amd64_vm86(2).
libi386 (-li386)
i386 I/O and memory access functions. See
i386_get_ioperm(2),
i386_get_ldt(2), i386_iopl(2), and i386_vm86(2).
The system libraries are located in /usr/lib. Typically, a
library will
have a number of variants:
libc.a
libc.so.30.1
libc_p.a
libc_pic.a
Libraries with an `.a' suffix are static. When a program is
linked
against a library, all the library code will be linked into
the binary.
This means the binary can be run even when the libraries are
unavailable.
However, it can be inefficient with memory usage. The C
compiler, cc(1),
can be instructed to link statically by specifying the
-static flag.
Libraries with a `.so.X.Y' suffix are dynamic libraries.
When code is
compiled dynamically, the library code that the application
needs is not
linked into the binary. Instead, data structures are added
containing
information about which dynamic libraries to link with.
When the binary
is executed, the run-time linker ld.so(1) reads these data
structures,
and loads them at a virtual address using the mmap(2) system
call.
`X' represents the major number of the library, and `Y' represents the
minor number. In general, a binary will be able to use a
dynamic library
with a differing minor number, but the major numbers must
match. In the
example above, a binary linked with minor number `3' would
be linkable
against libc.so.30.1, while a binary linked with major number `31' would
not.
The advantages of dynamic libraries are that multiple instances of the
same program can share address space, and the physical size
of the binary
is smaller. The disadvantage is the added complexity that
comes with
loading the libraries dynamically, and the extra time taken
to load the
libraries. Of course, if the libraries are not available,
the binary
will be unable to execute. The C compiler, cc(1), can be
instructed to
link dynamically by specifying the -shared flag, although on
systems that
support it, this will be the default and need not be specified.
Libraries with a `_p.a' suffix are profiling libraries.
They contain extra
information suitable for analysing programs, such as execution speed
and call counts. This in turn can be interpreted by utilities such as
gprof(1). The C compiler, cc(1), can be instructed to generate profiling
code, or to link with profiling libraries, by specifying the
-pg flag.
Libraries with a `_pic.a' suffix contain position-independent code (PIC).
Normally, compilers produce relocatable code. Relocatable
code needs to
be modified at run-time, depending on where in memory it is
to be run.
PIC code does not need to be modified at run-time, but is
less efficient
than relocatable code. PIC code is used by shared libraries, which can
make them slower. The C compiler, cc(1), can be instructed
to generate
PIC code, or to link with PIC libraries, by specifying the
-fpic or -fPIC
flags.
With the exception of dynamic libraries, libraries are generated using
the ar(1) utility. The libraries contain an index to the
contents of the
library, stored within the library itself. The index lists
each symbol
defined by a member of a library that is a relocatable object file. This
speeds up linking to the library, and allows routines in the
library to
call each other regardless of their placement within the library. The
index is created by ranlib(1) and can be viewed using nm(1).
The building of PIC versions of libraries and dynamic libraries can be
prevented by setting the variable NOPIC in /etc/mk.conf.
The building of
profiling versions of libraries and/or dynamic libraries can
be prevented
by setting the variable NOPROFILE in /etc/mk.conf. See
mk.conf(5) for
more details.
/usr/lib/libasn1.a
/usr/lib/libbfd.a
/usr/lib/libc.a
/usr/lib/libcom_err.a
/usr/lib/libcompat.a
/usr/lib/libcrypto.a
/usr/lib/libcurses++.a
/usr/lib/libcurses.a
/usr/lib/libdes.a
/usr/lib/libedit.a
/usr/lib/libevent.a
/usr/lib/libfl.a
/usr/lib/libform.a
/usr/lib/libfrtbegin.a
/usr/lib/libg2c.a
/usr/lib/libgssapi.a
/usr/lib/libhdb.a
/usr/lib/libiberty.a
/usr/lib/libkadm5clnt.a
/usr/lib/libkadm5srv.a
/usr/lib/libkafs.a
/usr/lib/libkeynote.a
/usr/lib/libkrb5.a
/usr/lib/libkvm.a
/usr/lib/libl.a
/usr/lib/libm.a
/usr/lib/libmenu.a
/usr/lib/libmilter.a
/usr/lib/libmmalloc.a
/usr/lib/libncurses.a
/usr/lib/libobjc.a
/usr/lib/libocurses.a
/usr/lib/libopcodes.a
/usr/lib/libossaudio.a
/usr/lib/libotermcap.a
/usr/lib/libpanel.a
/usr/lib/libpcap.a
/usr/lib/libperl.a
/usr/lib/libpthread.a
/usr/lib/libreadline.a
/usr/lib/libresolv.a
/usr/lib/librpcsvc.a
/usr/lib/libsectok.a
/usr/lib/libskey.a
/usr/lib/libssl.a
/usr/lib/libstdc++.a
/usr/lib/libtermcap.a
/usr/lib/libtermlib.a
/usr/lib/libusbhid.a
/usr/lib/libutil.a
/usr/lib/libwrap.a
/usr/lib/liby.a
/usr/lib/libz.a
/usr/lib/libalpha.a
/usr/lib/libamd64.a
/usr/lib/libi386.a
ar(1), c++(1), cc(1), g77(1), gcc-local(1), gprof(1), ld(1),
ld.so(1),
lex(1), nm(1), perl(1), ranlib(1), yacc(1), intro(2), compress(3),
crypto(3), curses(3), des_crypt(3), editline(3), event(3),
form(3),
hosts_access(3), keynote(3), kvm(3), math(3), menu(3),
ocurses(3),
ossaudio(3), panel(3), pcap(3), pthreads(3), readline(3),
resolver(3),
rfc1413(3), rpc(3), sectok(3), skey(3), ssl(3), stdio(3),
termcap(3),
usbhid(3), keynote(4), mk.conf(5)
An intro manual appeared in Version 7 AT&T UNIX.
OpenBSD 3.6 June 5, 1993
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