posix.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

may affect what characters are considered \f(CW\*(C`isgraph\*(C'\fR.  Does not work
on Unicode characters code point 256 or higher.  Consider using regular
expressions and the \f(CW\*(C`/[[:graph:]]/\*(C'\fR construct instead.
.IP "islower" 8
.IX Item "islower"
This is identical to the C function, except that it can apply to
a single character or to a whole string.  Note that locale settings
may affect what characters are considered \f(CW\*(C`islower\*(C'\fR.  Does not work
on Unicode characters code point 256 or higher.  Consider using regular
expressions and the \f(CW\*(C`/[[:lower:]]/\*(C'\fR construct instead.  Do \fBnot\fR use
\&\f(CW\*(C`/[a\-z]/\*(C'\fR.
.IP "isprint" 8
.IX Item "isprint"
This is identical to the C function, except that it can apply to
a single character or to a whole string.  Note that locale settings
may affect what characters are considered \f(CW\*(C`isprint\*(C'\fR.  Does not work
on Unicode characters code point 256 or higher.  Consider using regular
expressions and the \f(CW\*(C`/[[:print:]]/\*(C'\fR construct instead.
.IP "ispunct" 8
.IX Item "ispunct"
This is identical to the C function, except that it can apply to
a single character or to a whole string.  Note that locale settings
may affect what characters are considered \f(CW\*(C`ispunct\*(C'\fR.  Does not work
on Unicode characters code point 256 or higher.  Consider using regular
expressions and the \f(CW\*(C`/[[:punct:]]/\*(C'\fR construct instead.
.IP "isspace" 8
.IX Item "isspace"
This is identical to the C function, except that it can apply to
a single character or to a whole string.  Note that locale settings
may affect what characters are considered \f(CW\*(C`isspace\*(C'\fR.  Does not work
on Unicode characters code point 256 or higher.  Consider using regular
expressions and the \f(CW\*(C`/[[:space:]]/\*(C'\fR construct instead, or the \f(CW\*(C`/\es/\*(C'\fR
construct.  (Note that \f(CW\*(C`/\es/\*(C'\fR and \f(CW\*(C`/[[:space:]]/\*(C'\fR are slightly
different in that \f(CW\*(C`/[[:space:]]/\*(C'\fR can normally match a vertical tab,
while \f(CW\*(C`/\es/\*(C'\fR does not.)
.IP "isupper" 8
.IX Item "isupper"
This is identical to the C function, except that it can apply to
a single character or to a whole string.  Note that locale settings
may affect what characters are considered \f(CW\*(C`isupper\*(C'\fR.  Does not work
on Unicode characters code point 256 or higher.  Consider using regular
expressions and the \f(CW\*(C`/[[:upper:]]/\*(C'\fR construct instead.  Do \fBnot\fR use
\&\f(CW\*(C`/[A\-Z]/\*(C'\fR.
.IP "isxdigit" 8
.IX Item "isxdigit"
This is identical to the C function, except that it can apply to a single
character or to a whole string.  Note that locale settings may affect what
characters are considered \f(CW\*(C`isxdigit\*(C'\fR (unlikely, but still possible).
Does not work on Unicode characters code point 256 or higher.
Consider using regular expressions and the \f(CW\*(C`/[[:xdigit:]]/\*(C'\fR
construct instead, or simply \f(CW\*(C`/[0\-9a\-f]/i\*(C'\fR.
.IP "kill" 8
.IX Item "kill"
This is identical to Perl's builtin \f(CW\*(C`kill()\*(C'\fR function for sending
signals to processes (often to terminate them), see \*(L"kill\*(R" in perlfunc.
.IP "labs" 8
.IX Item "labs"
(For returning absolute values of long integers.)
\&\fIlabs()\fR is C\-specific, see \*(L"abs\*(R" in perlfunc instead.
.IP "ldexp" 8
.IX Item "ldexp"
This is identical to the C function \f(CW\*(C`ldexp()\*(C'\fR
for multiplying floating point numbers with powers of two.
.Sp
.Vb 1
\&        $x_quadrupled = POSIX::ldexp($x, 2);
.Ve
.IP "ldiv" 8
.IX Item "ldiv"
(For computing dividends of long integers.)
\&\fIldiv()\fR is C\-specific, use \f(CW\*(C`/\*(C'\fR and \f(CW\*(C`int()\*(C'\fR instead.
.IP "link" 8
.IX Item "link"
This is identical to Perl's builtin \f(CW\*(C`link()\*(C'\fR function
for creating hard links into files, see \*(L"link\*(R" in perlfunc.
.IP "localeconv" 8
.IX Item "localeconv"
Get numeric formatting information.  Returns a reference to a hash
containing the current locale formatting values.
.Sp
Here is how to query the database for the \fBde\fR (Deutsch or German) locale.
.Sp
.Vb 10
\&        $loc = POSIX::setlocale( &POSIX::LC_ALL, "de" );
\&        print "Locale = $loc\en";
\&        $lconv = POSIX::localeconv();
\&        print "decimal_point    = ", $lconv\->{decimal_point},   "\en";
\&        print "thousands_sep    = ", $lconv\->{thousands_sep},   "\en";
\&        print "grouping = ", $lconv\->{grouping},        "\en";
\&        print "int_curr_symbol  = ", $lconv\->{int_curr_symbol}, "\en";
\&        print "currency_symbol  = ", $lconv\->{currency_symbol}, "\en";
\&        print "mon_decimal_point = ", $lconv\->{mon_decimal_point}, "\en";
\&        print "mon_thousands_sep = ", $lconv\->{mon_thousands_sep}, "\en";
\&        print "mon_grouping     = ", $lconv\->{mon_grouping},    "\en";
\&        print "positive_sign    = ", $lconv\->{positive_sign},   "\en";
\&        print "negative_sign    = ", $lconv\->{negative_sign},   "\en";
\&        print "int_frac_digits  = ", $lconv\->{int_frac_digits}, "\en";
\&        print "frac_digits      = ", $lconv\->{frac_digits},     "\en";
\&        print "p_cs_precedes    = ", $lconv\->{p_cs_precedes},   "\en";
\&        print "p_sep_by_space   = ", $lconv\->{p_sep_by_space},  "\en";
\&        print "n_cs_precedes    = ", $lconv\->{n_cs_precedes},   "\en";
\&        print "n_sep_by_space   = ", $lconv\->{n_sep_by_space},  "\en";
\&        print "p_sign_posn      = ", $lconv\->{p_sign_posn},     "\en";
\&        print "n_sign_posn      = ", $lconv\->{n_sign_posn},     "\en";
.Ve
.IP "localtime" 8
.IX Item "localtime"
This is identical to Perl's builtin \f(CW\*(C`localtime()\*(C'\fR function for
converting seconds since the epoch to a date see \*(L"localtime\*(R" in perlfunc.
.IP "log" 8
.IX Item "log"
This is identical to Perl's builtin \f(CW\*(C`log()\*(C'\fR function,
returning the natural (\fIe\fR\-based) logarithm of the numerical argument,
see \*(L"log\*(R" in perlfunc.
.IP "log10" 8
.IX Item "log10"
This is identical to the C function \f(CW\*(C`log10()\*(C'\fR,
returning the 10\-base logarithm of the numerical argument.
You can also use
.Sp
.Vb 1
\&    sub log10 { log($_[0]) / log(10) }
.Ve
.Sp
or
.Sp
.Vb 1
\&    sub log10 { log($_[0]) / 2.30258509299405 }
.Ve
.Sp
or
.Sp
.Vb 1
\&    sub log10 { log($_[0]) * 0.434294481903252 }
.Ve
.IP "longjmp" 8
.IX Item "longjmp"
\&\fIlongjmp()\fR is C\-specific: use \*(L"die\*(R" in perlfunc instead.
.IP "lseek" 8
.IX Item "lseek"
Move the file's read/write position.  This uses file descriptors such as
those obtained by calling \f(CW\*(C`POSIX::open\*(C'\fR.
.Sp
.Vb 2
\&        $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
\&        $off_t = POSIX::lseek( $fd, 0, &POSIX::SEEK_SET );
.Ve
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "malloc" 8
.IX Item "malloc"
\&\fImalloc()\fR is C\-specific.  Perl does memory management transparently.
.IP "mblen" 8
.IX Item "mblen"
This is identical to the C function \f(CW\*(C`mblen()\*(C'\fR.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
.IP "mbstowcs" 8
.IX Item "mbstowcs"
This is identical to the C function \f(CW\*(C`mbstowcs()\*(C'\fR.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
.IP "mbtowc" 8
.IX Item "mbtowc"
This is identical to the C function \f(CW\*(C`mbtowc()\*(C'\fR.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
.IP "memchr" 8
.IX Item "memchr"
\&\fImemchr()\fR is C\-specific, see \*(L"index\*(R" in perlfunc instead.
.IP "memcmp" 8
.IX Item "memcmp"
\&\fImemcmp()\fR is C\-specific, use \f(CW\*(C`eq\*(C'\fR instead, see perlop.
.IP "memcpy" 8
.IX Item "memcpy"
\&\fImemcpy()\fR is C\-specific, use \f(CW\*(C`=\*(C'\fR, see perlop, or see \*(L"substr\*(R" in perlfunc.
.IP "memmove" 8
.IX Item "memmove"
\&\fImemmove()\fR is C\-specific, use \f(CW\*(C`=\*(C'\fR, see perlop, or see \*(L"substr\*(R" in perlfunc.
.IP "memset" 8
.IX Item "memset"
\&\fImemset()\fR is C\-specific, use \f(CW\*(C`x\*(C'\fR instead, see perlop.
.IP "mkdir" 8
.IX Item "mkdir"
This is identical to Perl's builtin \f(CW\*(C`mkdir()\*(C'\fR function
for creating directories, see \*(L"mkdir\*(R" in perlfunc.
.IP "mkfifo" 8
.IX Item "mkfifo"
This is similar to the C function \f(CW\*(C`mkfifo()\*(C'\fR for creating
\&\s-1FIFO\s0 special files.
.Sp
.Vb 1
\&        if (mkfifo($path, $mode)) { ....
.Ve
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.  The \f(CW$mode\fR is similar to the
mode of \f(CW\*(C`mkdir()\*(C'\fR, see \*(L"mkdir\*(R" in perlfunc, though for \f(CW\*(C`mkfifo\*(C'\fR
you \fBmust\fR specify the \f(CW$mode\fR.
.IP "mktime" 8
.IX Item "mktime"
Convert date/time info to a calendar time.
.Sp
Synopsis:
.Sp
.Vb 1
\&        mktime(sec, min, hour, mday, mon, year, wday = 0, yday = 0, isdst = \-1)
.Ve
.Sp
The month (\f(CW\*(C`mon\*(C'\fR), weekday (\f(CW\*(C`wday\*(C'\fR), and yearday (\f(CW\*(C`yday\*(C'\fR) begin at zero.
I.e. January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1.  The
year (\f(CW\*(C`year\*(C'\fR) is given in years since 1900.  I.e. The year 1995 is 95; the
year 2001 is 101.  Consult your system's \f(CW\*(C`mktime()\*(C'\fR manpage for details
about these and the other arguments.
.Sp
Calendar time for December 12, 1995, at 10:30 am.
.Sp
.Vb 2
\&        $time_t = POSIX::mktime( 0, 30, 10, 12, 11, 95 );
\&        print "Date = ", POSIX::ctime($time_t);
.Ve
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "modf" 8
.IX Item "modf"
Return the integral and fractional parts of a floating-point number.
.Sp
.Vb 1
\&        ($fractional, $integral) = POSIX::modf( 3.14 );
.Ve
.IP "nice" 8
.IX Item "nice"
This is similar to the C function \f(CW\*(C`nice()\*(C'\fR, for changing
the scheduling preference of the current process.  Positive
arguments mean more polite process, negative values more
needy process.  Normal user processes can only be more polite.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "offsetof" 8
.IX Item "offsetof"
\&\fIoffsetof()\fR is C\-specific, you probably want to see \*(L"pack\*(R" in perlfunc instead.
.IP "open" 8
.IX Item "open"
Open a file for reading for writing.  This returns file descriptors, not
Perl filehandles.  Use \f(CW\*(C`POSIX::close\*(C'\fR to close the file.
.Sp
Open a file read-only with mode 0666.
.Sp
.Vb 1
\&        $fd = POSIX::open( "foo" );
.Ve
.Sp
Open a file for read and write.
.Sp
.Vb 1
\&        $fd = POSIX::open( "foo", &POSIX::O_RDWR );
.Ve
.Sp
Open a file for write, with truncation.
.Sp
.Vb 1
\&        $fd = POSIX::open( "foo", &POSIX::O_WRONLY | &POSIX::O_TRUNC );
.Ve
.Sp
Create a new file with mode 0640.  Set up the file for writing.
.Sp
.Vb 1
\&        $fd = POSIX::open( "foo", &POSIX::O_CREAT | &POSIX::O_WRONLY, 0640 );
.Ve
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.Sp
See also \*(L"sysopen\*(R" in perlfunc.
.IP "opendir" 8
.IX Item "opendir"
Open a directory for reading.
.Sp
.Vb 3
\&        $dir = POSIX::opendir( "/var" );
\&        @files = POSIX::readdir( $dir );
\&        POSIX::closedir( $dir );
.Ve
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "pathconf" 8
.IX Item "pathconf"
Retrieves the value of a configurable limit on a file or directory.
.Sp
The following will determine the maximum length of the longest allowable
pathname on the filesystem which holds \f(CW\*(C`/var\*(C'\fR.
.Sp
.Vb 1
\&        $path_max = POSIX::pathconf( "/var", &POSIX::_PC_PATH_MAX );
.Ve
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "pause" 8
.IX Item "pause"
This is similar to the C function \f(CW\*(C`pause()\*(C'\fR, which suspends
the execution of the current process until a signal is received.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "perror" 8
.IX Item "perror"
This is identical to the C function \f(CW\*(C`perror()\*(C'\fR, which outputs to the
standard error stream the specified message followed by \*(L": \*(R" and the
current error string.  Use the \f(CW\*(C`warn()\*(C'\fR function and the \f(CW$!\fR
variable instead, see \*(L"warn\*(R" in perlfunc and \*(L"$ERRNO\*(R" in perlvar.
.IP "pipe" 8
.IX Item "pipe"
Create an interprocess channel.  This returns file descriptors like those
returned by \f(CW\*(C`POSIX::open\*(C'\fR.
.Sp
.Vb 3
\&        my ($read, $write) = POSIX::pipe();
\&        POSIX::write( $write, "hello", 5 );
\&        POSIX::read( $read, $buf, 5 );
.Ve
.Sp
See also \*(L"pipe\*(R" in perlfunc.
.IP "pow" 8
.IX Item "pow"
Computes \f(CW$x\fR raised to the power \f(CW$exponent\fR.
.Sp
.Vb 1
\&        $ret = POSIX::pow( $x, $exponent );
.Ve
.Sp
You can also use the \f(CW\*(C`**\*(C'\fR operator, see perlop.
.IP "printf" 8
.IX Item "printf"
Formats and prints the specified arguments to \s-1STDOUT\s0.
See also \*(L"printf\*(R" in perlfunc.
.IP "putc" 8
.IX Item "putc"
\&\fIputc()\fR is C\-specific, see \*(L"print\*(R" in perlfunc instead.
.IP "putchar" 8
.IX Item "putchar"
\&\fIputchar()\fR is C\-specific, see \*(L"print\*(R" in perlfunc instead.
.IP "puts" 8
.IX Item "puts"
\&\fIputs()\fR is C\-specific, see \*(L"print\*(R" in perlfunc instead.
.IP "qsort" 8
.IX Item "qsort"
\&\fIqsort()\fR is C\-specific, see \*(L"sort\*(R" in perlfunc instead.
.IP "raise" 8