posix.3

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.IX Item "raise"
Sends the specified signal to the current process.
See also \*(L"kill\*(R" in perlfunc and the \f(CW$$\fR in \*(L"$PID\*(R" in perlvar.
.IP "rand" 8
.IX Item "rand"
\&\f(CW\*(C`rand()\*(C'\fR is non-portable, see \*(L"rand\*(R" in perlfunc instead.
.IP "read" 8
.IX Item "read"
Read from a file.  This uses file descriptors such as those obtained by
calling \f(CW\*(C`POSIX::open\*(C'\fR.  If the buffer \f(CW$buf\fR is not large enough for the
read then Perl will extend it to make room for the request.
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.Vb 2
\&        $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
\&        $bytes = POSIX::read( $fd, $buf, 3 );
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
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See also \*(L"sysread\*(R" in perlfunc.
.IP "readdir" 8
.IX Item "readdir"
This is identical to Perl's builtin \f(CW\*(C`readdir()\*(C'\fR function
for reading directory entries, see \*(L"readdir\*(R" in perlfunc.
.IP "realloc" 8
.IX Item "realloc"
\&\fIrealloc()\fR is C\-specific.  Perl does memory management transparently.
.IP "remove" 8
.IX Item "remove"
This is identical to Perl's builtin \f(CW\*(C`unlink()\*(C'\fR function
for removing files, see \*(L"unlink\*(R" in perlfunc.
.IP "rename" 8
.IX Item "rename"
This is identical to Perl's builtin \f(CW\*(C`rename()\*(C'\fR function
for renaming files, see \*(L"rename\*(R" in perlfunc.
.IP "rewind" 8
.IX Item "rewind"
Seeks to the beginning of the file.
.IP "rewinddir" 8
.IX Item "rewinddir"
This is identical to Perl's builtin \f(CW\*(C`rewinddir()\*(C'\fR function for
rewinding directory entry streams, see \*(L"rewinddir\*(R" in perlfunc.
.IP "rmdir" 8
.IX Item "rmdir"
This is identical to Perl's builtin \f(CW\*(C`rmdir()\*(C'\fR function
for removing (empty) directories, see \*(L"rmdir\*(R" in perlfunc.
.IP "scanf" 8
.IX Item "scanf"
\&\fIscanf()\fR is C\-specific, use <> and regular expressions instead,
see perlre.
.IP "setgid" 8
.IX Item "setgid"
Sets the real group identifier and the effective group identifier for
this process.  Similar to assigning a value to the Perl's builtin
\&\f(CW$)\fR variable, see \*(L"$EGID\*(R" in perlvar, except that the latter
will change only the real user identifier, and that the \fIsetgid()\fR
uses only a single numeric argument, as opposed to a space-separated
list of numbers.
.IP "setjmp" 8
.IX Item "setjmp"
\&\f(CW\*(C`setjmp()\*(C'\fR is C\-specific: use \f(CW\*(C`eval {}\*(C'\fR instead,
see \*(L"eval\*(R" in perlfunc.
.IP "setlocale" 8
.IX Item "setlocale"
Modifies and queries program's locale.  The following examples assume
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.Vb 1
\&        use POSIX qw(setlocale LC_ALL LC_CTYPE);
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has been issued.
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The following will set the traditional \s-1UNIX\s0 system locale behavior
(the second argument \f(CW"C"\fR).
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.Vb 1
\&        $loc = setlocale( LC_ALL, "C" );
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The following will query the current \s-1LC_CTYPE\s0 category.  (No second
argument means 'query'.)
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.Vb 1
\&        $loc = setlocale( LC_CTYPE );
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The following will set the \s-1LC_CTYPE\s0 behaviour according to the locale
environment variables (the second argument \f(CW""\fR).
Please see your systems \f(CWsetlocale(3)\fR documentation for the locale
environment variables' meaning or consult perllocale.
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.Vb 1
\&        $loc = setlocale( LC_CTYPE, "" );
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The following will set the \s-1LC_COLLATE\s0 behaviour to Argentinian
Spanish. \fB\s-1NOTE\s0\fR: The naming and availability of locales depends on
your operating system. Please consult perllocale for how to find
out which locales are available in your system.
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.Vb 1
\&        $loc = setlocale( LC_ALL, "es_AR.ISO8859\-1" );
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.IP "setpgid" 8
.IX Item "setpgid"
This is similar to the C function \f(CW\*(C`setpgid()\*(C'\fR for
setting the process group identifier of the current process.
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "setsid" 8
.IX Item "setsid"
This is identical to the C function \f(CW\*(C`setsid()\*(C'\fR for
setting the session identifier of the current process.
.IP "setuid" 8
.IX Item "setuid"
Sets the real user identifier and the effective user identifier for
this process.  Similar to assigning a value to the Perl's builtin
\&\f(CW$<\fR variable, see \*(L"$UID\*(R" in perlvar, except that the latter
will change only the real user identifier.
.IP "sigaction" 8
.IX Item "sigaction"
Detailed signal management.  This uses \f(CW\*(C`POSIX::SigAction\*(C'\fR objects for
the \f(CW\*(C`action\*(C'\fR and \f(CW\*(C`oldaction\*(C'\fR arguments (the oldaction can also be
just a hash reference).  Consult your system's \f(CW\*(C`sigaction\*(C'\fR manpage
for details, see also \f(CW\*(C`POSIX::SigRt\*(C'\fR.
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Synopsis:
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.Vb 1
\&        sigaction(signal, action, oldaction = 0)
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Returns \f(CW\*(C`undef\*(C'\fR on failure.  The \f(CW\*(C`signal\*(C'\fR must be a number (like
\&\s-1SIGHUP\s0), not a string (like \*(L"\s-1SIGHUP\s0\*(R"), though Perl does try hard
to understand you.
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If you use the \s-1SA_SIGINFO\s0 flag, the signal handler will in addition to
the first argument, the signal name, also receive a second argument, a
hash reference, inside which are the following keys with the following
semantics, as defined by POSIX/SUSv3:
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.Vb 5
\&    signo       the signal number
\&    errno       the error number
\&    code        if this is zero or less, the signal was sent by
\&                a user process and the uid and pid make sense,
\&                otherwise the signal was sent by the kernel
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The following are also defined by POSIX/SUSv3, but unfortunately
not very widely implemented:
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.Vb 4
\&    pid         the process id generating the signal
\&    uid         the uid of the process id generating the signal
\&    status      exit value or signal for SIGCHLD
\&    band        band event for SIGPOLL
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A third argument is also passed to the handler, which contains a copy
of the raw binary contents of the siginfo structure: if a system has
some non-POSIX fields, this third argument is where to \fIunpack()\fR them
from.
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Note that not all siginfo values make sense simultaneously (some are
valid only for certain signals, for example), and not all values make
sense from Perl perspective, you should to consult your system's
\&\f(CW\*(C`sigaction\*(C'\fR and possibly also \f(CW\*(C`siginfo\*(C'\fR documentation.
.IP "siglongjmp" 8
.IX Item "siglongjmp"
\&\fIsiglongjmp()\fR is C\-specific: use \*(L"die\*(R" in perlfunc instead.
.IP "sigpending" 8
.IX Item "sigpending"
Examine signals that are blocked and pending.  This uses \f(CW\*(C`POSIX::SigSet\*(C'\fR
objects for the \f(CW\*(C`sigset\*(C'\fR argument.  Consult your system's \f(CW\*(C`sigpending\*(C'\fR
manpage for details.
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Synopsis:
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.Vb 1
\&        sigpending(sigset)
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "sigprocmask" 8
.IX Item "sigprocmask"
Change and/or examine calling process's signal mask.  This uses
\&\f(CW\*(C`POSIX::SigSet\*(C'\fR objects for the \f(CW\*(C`sigset\*(C'\fR and \f(CW\*(C`oldsigset\*(C'\fR arguments.
Consult your system's \f(CW\*(C`sigprocmask\*(C'\fR manpage for details.
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Synopsis:
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.Vb 1
\&        sigprocmask(how, sigset, oldsigset = 0)
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "sigsetjmp" 8
.IX Item "sigsetjmp"
\&\f(CW\*(C`sigsetjmp()\*(C'\fR is C\-specific: use \f(CW\*(C`eval {}\*(C'\fR instead,
see \*(L"eval\*(R" in perlfunc.
.IP "sigsuspend" 8
.IX Item "sigsuspend"
Install a signal mask and suspend process until signal arrives.  This uses
\&\f(CW\*(C`POSIX::SigSet\*(C'\fR objects for the \f(CW\*(C`signal_mask\*(C'\fR argument.  Consult your
system's \f(CW\*(C`sigsuspend\*(C'\fR manpage for details.
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Synopsis:
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.Vb 1
\&        sigsuspend(signal_mask)
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Returns \f(CW\*(C`undef\*(C'\fR on failure.
.IP "sin" 8
.IX Item "sin"
This is identical to Perl's builtin \f(CW\*(C`sin()\*(C'\fR function
for returning the sine of the numerical argument,
see \*(L"sin\*(R" in perlfunc.  See also Math::Trig.
.IP "sinh" 8
.IX Item "sinh"
This is identical to the C function \f(CW\*(C`sinh()\*(C'\fR
for returning the hyperbolic sine of the numerical argument.
See also Math::Trig.
.IP "sleep" 8
.IX Item "sleep"
This is functionally identical to Perl's builtin \f(CW\*(C`sleep()\*(C'\fR function
for suspending the execution of the current for process for certain
number of seconds, see \*(L"sleep\*(R" in perlfunc.  There is one significant
difference, however: \f(CW\*(C`POSIX::sleep()\*(C'\fR returns the number of
\&\fBunslept\fR seconds, while the \f(CW\*(C`CORE::sleep()\*(C'\fR returns the
number of slept seconds.
.IP "sprintf" 8
.IX Item "sprintf"
This is similar to Perl's builtin \f(CW\*(C`sprintf()\*(C'\fR function
for returning a string that has the arguments formatted as requested,
see \*(L"sprintf\*(R" in perlfunc.
.IP "sqrt" 8
.IX Item "sqrt"
This is identical to Perl's builtin \f(CW\*(C`sqrt()\*(C'\fR function.
for returning the square root of the numerical argument,
see \*(L"sqrt\*(R" in perlfunc.
.IP "srand" 8
.IX Item "srand"
Give a seed the pseudorandom number generator, see \*(L"srand\*(R" in perlfunc.
.IP "sscanf" 8
.IX Item "sscanf"
\&\fIsscanf()\fR is C\-specific, use regular expressions instead,
see perlre.
.IP "stat" 8
.IX Item "stat"
This is identical to Perl's builtin \f(CW\*(C`stat()\*(C'\fR function
for returning information about files and directories.
.IP "strcat" 8
.IX Item "strcat"
\&\fIstrcat()\fR is C\-specific, use \f(CW\*(C`.=\*(C'\fR instead, see perlop.
.IP "strchr" 8
.IX Item "strchr"
\&\fIstrchr()\fR is C\-specific, see \*(L"index\*(R" in perlfunc instead.
.IP "strcmp" 8
.IX Item "strcmp"
\&\fIstrcmp()\fR is C\-specific, use \f(CW\*(C`eq\*(C'\fR or \f(CW\*(C`cmp\*(C'\fR instead, see perlop.
.IP "strcoll" 8
.IX Item "strcoll"
This is identical to the C function \f(CW\*(C`strcoll()\*(C'\fR
for collating (comparing) strings transformed using
the \f(CW\*(C`strxfrm()\*(C'\fR function.  Not really needed since
Perl can do this transparently, see perllocale.
.IP "strcpy" 8
.IX Item "strcpy"
\&\fIstrcpy()\fR is C\-specific, use \f(CW\*(C`=\*(C'\fR instead, see perlop.
.IP "strcspn" 8
.IX Item "strcspn"
\&\fIstrcspn()\fR is C\-specific, use regular expressions instead,
see perlre.
.IP "strerror" 8
.IX Item "strerror"
Returns the error string for the specified errno.
Identical to the string form of the \f(CW$!\fR, see \*(L"$ERRNO\*(R" in perlvar.
.IP "strftime" 8
.IX Item "strftime"
Convert date and time information to string.  Returns the string.
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Synopsis:
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.Vb 1
\&        strftime(fmt, sec, min, hour, mday, mon, year, wday = \-1, yday = \-1, isdst = \-1)
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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`strftime()\*(C'\fR manpage for details
about these and the other arguments.
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If you want your code to be portable, your format (\f(CW\*(C`fmt\*(C'\fR) argument
should use only the conversion specifiers defined by the \s-1ANSI\s0 C
standard (C89, to play safe).  These are \f(CW\*(C`aAbBcdHIjmMpSUwWxXyYZ%\*(C'\fR.
But even then, the \fBresults\fR of some of the conversion specifiers are
non-portable.  For example, the specifiers \f(CW\*(C`aAbBcpZ\*(C'\fR change according
to the locale settings of the user, and both how to set locales (the
locale names) and what output to expect are non-standard.
The specifier \f(CW\*(C`c\*(C'\fR changes according to the timezone settings of the
user and the timezone computation rules of the operating system.
The \f(CW\*(C`Z\*(C'\fR specifier is notoriously unportable since the names of
timezones are non-standard. Sticking to the numeric specifiers is the
safest route.
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The given arguments are made consistent as though by calling
\&\f(CW\*(C`mktime()\*(C'\fR before calling your system's \f(CW\*(C`strftime()\*(C'\fR function,
except that the \f(CW\*(C`isdst\*(C'\fR value is not affected.
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The string for Tuesday, December 12, 1995.
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.Vb 2
\&        $str = POSIX::strftime( "%A, %B %d, %Y", 0, 0, 0, 12, 11, 95, 2 );
\&        print "$str\en";
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.IP "strlen" 8
.IX Item "strlen"
\&\fIstrlen()\fR is C\-specific, use \f(CW\*(C`length()\*(C'\fR instead, see \*(L"length\*(R" in perlfunc.
.IP "strncat" 8
.IX Item "strncat"
\&\fIstrncat()\fR is C\-specific, use \f(CW\*(C`.=\*(C'\fR instead, see perlop.
.IP "strncmp" 8
.IX Item "strncmp"
\&\fIstrncmp()\fR is C\-specific, use \f(CW\*(C`eq\*(C'\fR instead, see perlop.
.IP "strncpy" 8
.IX Item "strncpy"
\&\fIstrncpy()\fR is C\-specific, use \f(CW\*(C`=\*(C'\fR instead, see perlop.
.IP "strpbrk" 8
.IX Item "strpbrk"
\&\fIstrpbrk()\fR is C\-specific, use regular expressions instead,
see perlre.
.IP "strrchr" 8
.IX Item "strrchr"
\&\fIstrrchr()\fR is C\-specific, see \*(L"rindex\*(R" in perlfunc instead.
.IP "strspn" 8
.IX Item "strspn"
\&\fIstrspn()\fR is C\-specific, use regular expressions instead,
see perlre.
.IP "strstr" 8
.IX Item "strstr"
This is identical to Perl's builtin \f(CW\*(C`index()\*(C'\fR function,
see \*(L"index\*(R" in perlfunc.
.IP "strtod" 8
.IX Item "strtod"
String to double translation. Returns the parsed number and the number