posix.3

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of characters in the unparsed portion of the string.  Truly
POSIX-compliant systems set $! ($ERRNO) to indicate a translation
error, so clear $! before calling strtod.  However, non-POSIX systems
may not check for overflow, and therefore will never set $!.
.Sp
strtod should respect any \s-1POSIX\s0 \fI\fIsetlocale()\fI\fR settings.
.Sp
To parse a string \f(CW$str\fR as a floating point number use
.Sp
.Vb 2
\&    $! = 0;
\&    ($num, $n_unparsed) = POSIX::strtod($str);
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The second returned item and $! can be used to check for valid input:
.Sp
.Vb 3
\&    if (($str eq \*(Aq\*(Aq) || ($n_unparsed != 0) || $!) {
\&        die "Non\-numeric input $str" . ($! ? ": $!\en" : "\en");
\&    }
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When called in a scalar context strtod returns the parsed number.
.IP "strtok" 8
.IX Item "strtok"
\&\fIstrtok()\fR is C\-specific, use regular expressions instead, see
perlre, or \*(L"split\*(R" in perlfunc.
.IP "strtol" 8
.IX Item "strtol"
String to (long) integer translation.  Returns the parsed number and
the number of characters in the unparsed portion of the string.  Truly
POSIX-compliant systems set $! ($ERRNO) to indicate a translation
error, so clear $! before calling strtol.  However, non-POSIX systems
may not check for overflow, and therefore will never set $!.
.Sp
strtol should respect any \s-1POSIX\s0 \fI\fIsetlocale()\fI\fR settings.
.Sp
To parse a string \f(CW$str\fR as a number in some base \f(CW$base\fR use
.Sp
.Vb 2
\&    $! = 0;
\&    ($num, $n_unparsed) = POSIX::strtol($str, $base);
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The base should be zero or between 2 and 36, inclusive.  When the base
is zero or omitted strtol will use the string itself to determine the
base: a leading \*(L"0x\*(R" or \*(L"0X\*(R" means hexadecimal; a leading \*(L"0\*(R" means
octal; any other leading characters mean decimal.  Thus, \*(L"1234\*(R" is
parsed as a decimal number, \*(L"01234\*(R" as an octal number, and \*(L"0x1234\*(R"
as a hexadecimal number.
.Sp
The second returned item and $! can be used to check for valid input:
.Sp
.Vb 3
\&    if (($str eq \*(Aq\*(Aq) || ($n_unparsed != 0) || !$!) {
\&        die "Non\-numeric input $str" . $! ? ": $!\en" : "\en";
\&    }
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.Sp
When called in a scalar context strtol returns the parsed number.
.IP "strtoul" 8
.IX Item "strtoul"
String to unsigned (long) integer translation.  \fIstrtoul()\fR is identical
to \fIstrtol()\fR except that \fIstrtoul()\fR only parses unsigned integers.  See
\&\*(L"strtol\*(R" for details.
.Sp
Note: Some vendors supply \fIstrtod()\fR and \fIstrtol()\fR but not \fIstrtoul()\fR.
Other vendors that do supply \fIstrtoul()\fR parse \*(L"\-1\*(R" as a valid value.
.IP "strxfrm" 8
.IX Item "strxfrm"
String transformation.  Returns the transformed string.
.Sp
.Vb 1
\&        $dst = POSIX::strxfrm( $src );
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Used in conjunction with the \f(CW\*(C`strcoll()\*(C'\fR function, see \*(L"strcoll\*(R".
.Sp
Not really needed since Perl can do this transparently, see
perllocale.
.IP "sysconf" 8
.IX Item "sysconf"
Retrieves values of system configurable variables.
.Sp
The following will get the machine's clock speed.
.Sp
.Vb 1
\&        $clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "system" 8
.IX Item "system"
This is identical to Perl's builtin \f(CW\*(C`system()\*(C'\fR function, see
\&\*(L"system\*(R" in perlfunc.
.IP "tan" 8
.IX Item "tan"
This is identical to the C function \f(CW\*(C`tan()\*(C'\fR, returning the
tangent of the numerical argument.  See also Math::Trig.
.IP "tanh" 8
.IX Item "tanh"
This is identical to the C function \f(CW\*(C`tanh()\*(C'\fR, returning the
hyperbolic tangent of the numerical argument.   See also Math::Trig.
.IP "tcdrain" 8
.IX Item "tcdrain"
This is similar to the C function \f(CW\*(C`tcdrain()\*(C'\fR for draining
the output queue of its argument stream.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "tcflow" 8
.IX Item "tcflow"
This is similar to the C function \f(CW\*(C`tcflow()\*(C'\fR for controlling
the flow of its argument stream.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "tcflush" 8
.IX Item "tcflush"
This is similar to the C function \f(CW\*(C`tcflush()\*(C'\fR for flushing
the I/O buffers of its argument stream.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "tcgetpgrp" 8
.IX Item "tcgetpgrp"
This is identical to the C function \f(CW\*(C`tcgetpgrp()\*(C'\fR for returning the
process group identifier of the foreground process group of the controlling
terminal.
.IP "tcsendbreak" 8
.IX Item "tcsendbreak"
This is similar to the C function \f(CW\*(C`tcsendbreak()\*(C'\fR for sending
a break on its argument stream.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "tcsetpgrp" 8
.IX Item "tcsetpgrp"
This is similar to the C function \f(CW\*(C`tcsetpgrp()\*(C'\fR for setting the
process group identifier of the foreground process group of the controlling
terminal.
.Sp
Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "time" 8
.IX Item "time"
This is identical to Perl's builtin \f(CW\*(C`time()\*(C'\fR function
for returning the number of seconds since the epoch
(whatever it is for the system), see \*(L"time\*(R" in perlfunc.
.IP "times" 8
.IX Item "times"
The \fItimes()\fR function returns elapsed realtime since some point in the past
(such as system startup), user and system times for this process, and user
and system times used by child processes.  All times are returned in clock
ticks.
.Sp
.Vb 1
\&    ($realtime, $user, $system, $cuser, $csystem) = POSIX::times();
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.Sp
Note: Perl's builtin \f(CW\*(C`times()\*(C'\fR function returns four values, measured in
seconds.
.IP "tmpfile" 8
.IX Item "tmpfile"
Use method \f(CW\*(C`IO::File::new_tmpfile()\*(C'\fR instead, or see File::Temp.
.IP "tmpnam" 8
.IX Item "tmpnam"
Returns a name for a temporary file.
.Sp
.Vb 1
\&        $tmpfile = POSIX::tmpnam();
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.Sp
For security reasons, which are probably detailed in your system's
documentation for the C library \fItmpnam()\fR function, this interface
should not be used; instead see File::Temp.
.IP "tolower" 8
.IX Item "tolower"
This is identical to the C function, except that it can apply to a single
character or to a whole string.  Consider using the \f(CW\*(C`lc()\*(C'\fR function,
see \*(L"lc\*(R" in perlfunc, or the equivalent \f(CW\*(C`\eL\*(C'\fR operator inside doublequotish
strings.
.IP "toupper" 8
.IX Item "toupper"
This is identical to the C function, except that it can apply to a single
character or to a whole string.  Consider using the \f(CW\*(C`uc()\*(C'\fR function,
see \*(L"uc\*(R" in perlfunc, or the equivalent \f(CW\*(C`\eU\*(C'\fR operator inside doublequotish
strings.
.IP "ttyname" 8
.IX Item "ttyname"
This is identical to the C function \f(CW\*(C`ttyname()\*(C'\fR for returning the
name of the current terminal.
.IP "tzname" 8
.IX Item "tzname"
Retrieves the time conversion information from the \f(CW\*(C`tzname\*(C'\fR variable.
.Sp
.Vb 2
\&        POSIX::tzset();
\&        ($std, $dst) = POSIX::tzname();
.Ve
.IP "tzset" 8
.IX Item "tzset"
This is identical to the C function \f(CW\*(C`tzset()\*(C'\fR for setting
the current timezone based on the environment variable \f(CW\*(C`TZ\*(C'\fR,
to be used by \f(CW\*(C`ctime()\*(C'\fR, \f(CW\*(C`localtime()\*(C'\fR, \f(CW\*(C`mktime()\*(C'\fR, and \f(CW\*(C`strftime()\*(C'\fR
functions.
.IP "umask" 8
.IX Item "umask"
This is identical to Perl's builtin \f(CW\*(C`umask()\*(C'\fR function
for setting (and querying) the file creation permission mask,
see \*(L"umask\*(R" in perlfunc.
.IP "uname" 8
.IX Item "uname"
Get name of current operating system.
.Sp
.Vb 1
\&        ($sysname, $nodename, $release, $version, $machine) = POSIX::uname();
.Ve
.Sp
Note that the actual meanings of the various fields are not
that well standardized, do not expect any great portability.
The \f(CW$sysname\fR might be the name of the operating system,
the \f(CW$nodename\fR might be the name of the host, the \f(CW$release\fR
might be the (major) release number of the operating system,
the \f(CW$version\fR might be the (minor) release number of the
operating system, and the \f(CW$machine\fR might be a hardware identifier.
Maybe.
.IP "ungetc" 8
.IX Item "ungetc"
Use method \f(CW\*(C`IO::Handle::ungetc()\*(C'\fR instead.
.IP "unlink" 8
.IX Item "unlink"
This is identical to Perl's builtin \f(CW\*(C`unlink()\*(C'\fR function
for removing files, see \*(L"unlink\*(R" in perlfunc.
.IP "utime" 8
.IX Item "utime"
This is identical to Perl's builtin \f(CW\*(C`utime()\*(C'\fR function
for changing the time stamps of files and directories,
see \*(L"utime\*(R" in perlfunc.
.IP "vfprintf" 8
.IX Item "vfprintf"
\&\fIvfprintf()\fR is C\-specific, see \*(L"printf\*(R" in perlfunc instead.
.IP "vprintf" 8
.IX Item "vprintf"
\&\fIvprintf()\fR is C\-specific, see \*(L"printf\*(R" in perlfunc instead.
.IP "vsprintf" 8
.IX Item "vsprintf"
\&\fIvsprintf()\fR is C\-specific, see \*(L"sprintf\*(R" in perlfunc instead.
.IP "wait" 8
.IX Item "wait"
This is identical to Perl's builtin \f(CW\*(C`wait()\*(C'\fR function,
see \*(L"wait\*(R" in perlfunc.
.IP "waitpid" 8
.IX Item "waitpid"
Wait for a child process to change state.  This is identical to Perl's
builtin \f(CW\*(C`waitpid()\*(C'\fR function, see \*(L"waitpid\*(R" in perlfunc.
.Sp
.Vb 2
\&        $pid = POSIX::waitpid( \-1, POSIX::WNOHANG );
\&        print "status = ", ($? / 256), "\en";
.Ve
.IP "wcstombs" 8
.IX Item "wcstombs"
This is identical to the C function \f(CW\*(C`wcstombs()\*(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 "wctomb" 8
.IX Item "wctomb"
This is identical to the C function \f(CW\*(C`wctomb()\*(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 "write" 8
.IX Item "write"
Write to a file.  This uses file descriptors such as those obtained by
calling \f(CW\*(C`POSIX::open\*(C'\fR.
.Sp
.Vb 3
\&        $fd = POSIX::open( "foo", &POSIX::O_WRONLY );
\&        $buf = "hello";
\&        $bytes = POSIX::write( $b, $buf, 5 );
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
.Sp
See also \*(L"syswrite\*(R" in perlfunc.
.SH "CLASSES"
.IX Header "CLASSES"
.Sh "POSIX::SigAction"
.IX Subsection "POSIX::SigAction"
.IP "new" 8
.IX Item "new"
Creates a new \f(CW\*(C`POSIX::SigAction\*(C'\fR object which corresponds to the C
\&\f(CW\*(C`struct sigaction\*(C'\fR.  This object will be destroyed automatically when
it is no longer needed.  The first parameter is the handler, a sub
reference.  The second parameter is a \f(CW\*(C`POSIX::SigSet\*(C'\fR object, it
defaults to the empty set.  The third parameter contains the
\&\f(CW\*(C`sa_flags\*(C'\fR, it defaults to 0.
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.Vb 2
\&        $sigset = POSIX::SigSet\->new(SIGINT, SIGQUIT);
\&        $sigaction = POSIX::SigAction\->new( \e&handler, $sigset, &POSIX::SA_NOCLDSTOP );
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This \f(CW\*(C`POSIX::SigAction\*(C'\fR object is intended for use with the \f(CW\*(C`POSIX::sigaction()\*(C'\fR
function.
.IP "handler" 8
.IX Item "handler"
.PD 0
.IP "mask" 8
.IX Item "mask"
.IP "flags" 8
.IX Item "flags"
.PD
accessor functions to get/set the values of a SigAction object.
.Sp
.Vb 2
\&        $sigset = $sigaction\->mask;
\&        $sigaction\->flags(&POSIX::SA_RESTART);
.Ve
.IP "safe" 8
.IX Item "safe"
accessor function for the \*(L"safe signals\*(R" flag of a SigAction object; see
perlipc for general information on safe (a.k.a. \*(L"deferred\*(R") signals.  If
you wish to handle a signal safely, use this accessor to set the \*(L"safe\*(R" flag
in the \f(CW\*(C`POSIX::SigAction\*(C'\fR object:
.Sp
.Vb 1
\&        $sigaction\->safe(1);
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.Sp
You may also examine the \*(L"safe\*(R" flag on the output action object which is
filled in when given as the third parameter to \f(CW\*(C`POSIX::sigaction()\*(C'\fR:
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.Vb 4
\&        sigaction(SIGINT, $new_action, $old_action);
\&        if ($old_action\->safe) {
\&            # previous SIGINT handler used safe signals
\&        }
.Ve
.Sh "POSIX::SigRt"
.IX Subsection "POSIX::SigRt"
.ie n .IP "%SIGRT" 8
.el .IP "\f(CW%SIGRT\fR" 8
.IX Item "%SIGRT"
A hash of the \s-1POSIX\s0 realtime signal handlers.  It is an extension of
the standard \f(CW%SIG\fR, the \f(CW$POSIX::SIGRT\fR{\s-1SIGRTMIN\s0} is roughly equivalent
to \f(CW$SIG\fR{\s-1SIGRTMIN\s0}, but the right \s-1POSIX\s0 moves (see below) are made with
the POSIX::SigSet and POSIX::sigaction instead of accessing the \f(CW%SIG\fR.
.Sp
You can set the \f(CW%POSIX::SIG