unistd.h.html

posix标准英文,html格式

<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
void         encrypt(char[64], int);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          execl(const char *, const char *, ...);
int          execle(const char *, const char *, ...);
int          execlp(const char *, const char *, ...);
int          execv(const char *, char *const []);
int          execve(const char *, char *const [], char *const []);
int          execvp(const char *, char *const []);
void        _exit(int);
int          fchown(int, uid_t, gid_t);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          fchdir(int);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
<sup>[<a href="javascript:open_code('SIO')">SIO</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          fdatasync(int);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
pid_t        fork(void);
long         fpathconf(int, int);
<sup>[<a href="javascript:open_code('FSC')">FSC</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          fsync(int);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          ftruncate(int, off_t);
char        *getcwd(char *, size_t);
gid_t        getegid(void);
uid_t        geteuid(void);
gid_t        getgid(void);
int          getgroups(int, gid_t []);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
long         gethostid(void);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          gethostname(char *, size_t);
char        *getlogin(void);
int          getlogin_r(char *, size_t);
int          getopt(int, char * const [], const char *);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
pid_t        getpgid(pid_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
pid_t        getpgrp(void);
pid_t        getpid(void);
pid_t        getppid(void);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
pid_t        getsid(pid_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
uid_t        getuid(void);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
char        *getwd(char *); (</tt><b>LEGACY</b> <tt>)
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          isatty(int);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          lchown(const char *, uid_t, gid_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          link(const char *, const char *);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          lockf(int, int, off_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
off_t        lseek(int, off_t, int);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          nice(int);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
long         pathconf(const char *, int);
int          pause(void);
int          pipe(int [2]);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
ssize_t      pread(int, void *, size_t, off_t);
ssize_t      pwrite(int, const void *, size_t, off_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
ssize_t      read(int, void *, size_t);
ssize_t      readlink(const char *restrict, char *restrict, size_t);
int          rmdir(const char *);
int          setegid(gid_t);
int          seteuid(uid_t);
int          setgid(gid_t);
<br>
int          setpgid(pid_t, pid_t);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
pid_t        setpgrp(void);
int          setregid(gid_t, gid_t);
int          setreuid(uid_t, uid_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
pid_t        setsid(void);
int          setuid(uid_t);
unsigned     sleep(unsigned);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
void         swab(const void *restrict, void *restrict, ssize_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          symlink(const char *, const char *);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
void         sync(void);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
long         sysconf(int);
pid_t        tcgetpgrp(int);
int          tcsetpgrp(int, pid_t);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          truncate(const char *, off_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
char        *ttyname(int);
int          ttyname_r(int, char *, size_t);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
useconds_t   ualarm(useconds_t, useconds_t);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
int          unlink(const char *);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int          usleep(useconds_t);
pid_t        vfork(void);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
ssize_t      write(int, const void *, size_t);
</tt>
</pre>

<p>Implementations may also include the <a href="../functions/pthread_atfork.html"><i>pthread_atfork</i>()</a> prototype as defined
in <a href="pthread.h.html"><i>&lt;pthread.h&gt;</i></a>.</p>

<p>The following external variables shall be declared:</p>

<pre>
<tt>extern char  *optarg;
extern int    optind, opterr, optopt;
</tt>
</pre>
</blockquote>

<hr>
<div class="box"><em>The following sections are informative.</em></div>

<h4><a name="tag_13_80_04"></a>APPLICATION USAGE</h4>

<blockquote>
<p>IEEE&nbsp;Std&nbsp;1003.1-2001 only describes the behavior of systems that claim conformance to it. However, application
developers who want to write applications that adapt to other versions of IEEE&nbsp;Std&nbsp;1003.1 (or to systems that do not
conform to any POSIX standard) may find it useful to code them so as to conditionally compile different code depending on the value
of _POSIX_VERSION, for example:</p>

<pre>
<tt>#if _POSIX_VERSION &gt;= 200112L
/* Use the newer function that copes with large files. */
off_t pos=ftello(fp);
#else
/* Either this is an old version of POSIX, or _POSIX_VERSION is
   not even defined, so use the traditional function. */
long pos=ftell(fp);
#endif
</tt>
</pre>

<p>Earlier versions of IEEE&nbsp;Std&nbsp;1003.1 and of the Single UNIX Specification can be identified by the following
macros:</p>

<dl compact>
<dt>POSIX.1-1988 standard</dt>

<dd>
_POSIX_VERSION==198808L</dd>

<dt>POSIX.1-1990 standard</dt>

<dd>
_POSIX_VERSION==199009L</dd>

<dt>ISO&nbsp;POSIX-1:1996 standard</dt>

<dd>
_POSIX_VERSION==199506L</dd>

<dt>Single UNIX Specification, Version 1</dt>

<dd>
_XOPEN_UNIX and _XOPEN_VERSION==4</dd>

<dt>Single UNIX Specification, Version 2</dt>

<dd>
_XOPEN_UNIX and _XOPEN_VERSION==500</dd>
</dl>

<p>IEEE&nbsp;Std&nbsp;1003.1-2001 does not make any attempt to define application binary interaction with the underlying operating
system. However, application developers may find it useful to query _SC_VERSION at runtime via <a href=
"../functions/sysconf.html"><i>sysconf</i>()</a> to determine whether the current version of the operating system supports the
necessary functionality as in the following program fragment:</p>

<pre>
<tt>if (sysconf(_SC_VERSION) &lt; 200112L) {
    fprintf(stderr, "POSIX.1-2001 system required, terminating \n");
    exit(1);
}
</tt>
</pre>

<p>New applications should not use _XOPEN_SHM or _XOPEN_ENH_I18N.</p>
</blockquote>

<h4><a name="tag_13_80_05"></a>RATIONALE</h4>

<blockquote>
<p>As IEEE&nbsp;Std&nbsp;1003.1-2001 evolved, certain options became sufficiently standardized that it was concluded that simply
requiring one of the option choices was simpler than retaining the option. However, for backwards-compatibility, the option flags
(with required constant values) are retained.</p>

<h5><a name="tag_13_80_05_01"></a>Version Test Macros</h5>

<p>The standard developers considered altering the definition of _POSIX_VERSION and removing _SC_VERSION from the specification of
<a href="../functions/sysconf.html"><i>sysconf</i>()</a> since the utility to an application was deemed by some to be minimal, and
since the implementation of the functionality is potentially problematic. However, they recognized that support for existing
application binaries is a concern to manufacturers, application developers, and the users of implementations conforming to
IEEE&nbsp;Std&nbsp;1003.1-2001.</p>

<p>While the example using _SC_VERSION in the APPLICATION USAGE section does not provide the greatest degree of imaginable utility
to the application developer or user, it is arguably better than a <b>core</b> file or some other equally obscure result. (It is
also possible for implementations to encode and recognize application binaries compiled in various POSIX.1-conforming environments,
and modify the semantics of the underlying system to conform to the expectations of the application.) For the reasons outlined in
the preceding paragraphs and in the APPLICATION USAGE section, the standard developers elected to retain the _POSIX_VERSION and
_SC_VERSION functionality.</p>

<h5><a name="tag_13_80_05_02"></a>Compile-Time Symbolic Constants for System-Wide Options</h5>

<p>IEEE&nbsp;Std&nbsp;1003.1-2001 now includes support in certain areas for the newly adopted policy governing options and
stubs.</p>

<p>This policy provides flexibility for implementations in how they support options. It also specifies how conforming applications
can adapt to different implementations that support different sets of options. It allows the following:</p>

<ol>
<li>
<p>If an implementation has no interest in supporting an option, it does not have to provide anything associated with that option
beyond the announcement that it does not support it.</p>
</li>

<li>
<p>An implementation can support a partial or incompatible version of an option (as a non-standard extension) as long as it does
not claim to support the option.</p>
</li>

<li>
<p>An application can determine whether the option is supported. A strictly conforming application must check this announcement
mechanism before first using anything associated with the option.</p>
</li>
</ol>

<p>There is an important implication of this policy. IEEE&nbsp;Std&nbsp;1003.1-2001 cannot dictate the behavior of interfaces
associated with an option when the implementation does not claim to support the option. In particular, it cannot require that a
function associated with an unsupported option will fail if it does not perform as specified. However, this policy does not prevent
a standard from requiring certain functions to always be present, but that they shall always fail on some implementations. The <a
href="../functions/setpgid.html"><i>setpgid</i>()</a> function in the POSIX.1-1990 standard, for example, is considered
appropriate.</p>

<p>The POSIX standards include various options, and the C-language binding support for an option implies that the implementation
must supply data types and function interfaces. An application must be able to discover whether the implementation supports each
option.</p>

<p>Any application must consider the following three cases for each option:</p>

<ol>
<li>
<p>Option never supported.</p>

<p>The implementation advertises at compile time that the option will never be supported. In this case, it is not necessary for the
implementation to supply any of the data types or function interfaces that are provided only as part of the option. The
implementation might provide data types and functions that are similar to those defined by IEEE&nbsp;Std&nbsp;1003.1-2001, but
there is no guarantee for any particular behavior.</p>
</li>

<li>
<p>Option always supported.</p>

<p>The implementation advertises at compile time that the option will always be supported. In this case, all data types and
function interfaces shall be available and shall operate as specified.</p>
</li>

<li>
<p>Option might or might not be supported.</p>

<p>Some implementations might not provide a me