=item acos
This is identical to the C function C<acos()>, returning
-the arcus cosine of its numerical argument.
+the arcus cosine of its numerical argument. See also L<Math::Trig>.
=item alarm
=item asin
This is identical to the C function C<asin()>, returning
-the arcus sine of its numerical argument.
+the arcus sine of its numerical argument. See also L<Math::Trig>.
=item assert
=item atan
This is identical to the C function C<atan()>, returning the
-arcus tangent of its numerical argument.
+arcus tangent of its numerical argument. See also L<Math::Trig>.
=item atan2
This is identical to Perl's builtin C<atan2()> function, returning
the arcus tangent defined by its two numerical arguments, the I<y>
-coordinate and the I<x> coordinate.
+coordinate and the I<x> coordinate. See also L<Math::Trig>.
=item atexit
=item clearerr
-Use the method L<IO::Handle::clearerr()> instead, to reset the error
+Use the method C<IO::Handle::clearerr()> instead, to reset the error
state (if any) and EOF state (if any) of the given stream.
=item clock
This is identical to Perl's builtin C<cos()> function, for returning
the cosine of its numerical argument, see L<perlfunc/cos>.
+See also L<Math::Trig>.
=item cosh
This is identical to the C function C<cosh()>, for returning
-the hyperbolic cosine of its numeric argument.
+the hyperbolic cosine of its numeric argument. See also L<Math::Trig>.
=item creat
=item fclose
-Use method C<IO::Handle::close()> instead.
+Use method C<IO::Handle::close()> instead, or see L<perlfunc/close>.
=item fcntl
=item fdopen
-Use method C<IO::Handle::new_from_fd()> instead.
+Use method C<IO::Handle::new_from_fd()> instead, or see L<perlfunc/open>.
=item feof
-Use method C<IO::Handle::eof()> instead.
+Use method C<IO::Handle::eof()> instead, or see L<perlfunc/eof>.
=item ferror
=item fflush
Use method C<IO::Handle::flush()> instead.
+See also L<perlvar/$OUTPUT_AUTOFLUSH>.
=item fgetc
-Use method C<IO::Handle::getc()> instead.
+Use method C<IO::Handle::getc()> instead, or see L<perlfunc/read>.
=item fgetpos
-Use method C<IO::Seekable::getpos()> instead.
+Use method C<IO::Seekable::getpos()> instead, or see L<L/seek>.
=item fgets
=item fileno
-Use method C<IO::Handle::fileno()> instead.
+Use method C<IO::Handle::fileno()> instead, or see L<perlfunc/fileno>.
=item floor
=item fopen
-Use method C<IO::File::open()> instead.
+Use method C<IO::File::open()> instead, or see L<perlfunc/open>.
=item fork
-This is identical to Perl's builtin C<fork()> function.
+This is identical to Perl's builtin C<fork()> function
+for duplicating the current process, see L<perlfunc/fork>
+and L<perlfork> if you are in Windows.
=item fpathconf
=item fseek
-Use method C<IO::Seekable::seek()> instead.
+Use method C<IO::Seekable::seek()> instead, or see L<perlfunc/seek>.
=item fsetpos
-Use method C<IO::Seekable::setpos()> instead.
+Use method C<IO::Seekable::setpos()> instead, or seek L<perlfunc/seek>.
=item fstat
=item ftell
-Use method C<IO::Seekable::tell()> instead.
+Use method C<IO::Seekable::tell()> instead, or see L<perlfunc/tell>.
=item fwrite
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isalnum:]]/> construct instead, or possibly the C</\w/> construct.
+C</[[:alnum:]]/> construct instead, or possibly the C</\w/> construct.
=item isalpha
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isalpha:]]/> construct instead.
+C</[[:alpha:]]/> construct instead.
=item isatty
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:iscntrl:]]/> construct instead.
+C</[[:cntrl:]]/> construct instead.
=item isdigit
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isdigit:]]/> construct instead, or the C</\d/> construct.
+C</[[:digit:]]/> construct instead, or the C</\d/> construct.
=item isgraph
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isgraph:]]/> construct instead.
+C</[[:graph:]]/> construct instead.
=item islower
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:islower:]]/> construct instead. Do B<not> use C</a-z/>.
+C</[[:lower:]]/> construct instead. Do B<not> use C</[a-z]/>.
=item isprint
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isprint:]]/> construct instead.
+C</[[:print:]]/> construct instead.
=item ispunct
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:ispunct:]]/> construct instead.
+C</[[:punct:]]/> construct instead.
=item isspace
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isspace:]]/> construct instead, or the C</\s/> construct.
+C</[[:space:]]/> construct instead, or the C</\s/> construct.
+(Note that C</\s/> and C</[[:space:]]/> are slightly different in that
+C</[[:space:]]/> can normally match a vertical tab, while C</\s/> does
+not.)
=item isupper
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isupper:]]/> construct instead. Do B<not> use C</A-Z/>.
+C</[[:upper:]]/> construct instead. Do B<not> use C</[A-Z]/>.
=item isxdigit
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using regular expressions and the
-C</[[:isxdigit:]]/> construct instead, or simply C</[0-9a-f]/i>.
+C</[[:xdigit:]]/> construct instead, or simply C</[0-9a-f]/i>.
=item kill
This is identical to Perl's builtin C<kill()> function for sending
-signals to processes (oftern to terminate them), see L<perlfunc/kill>.
+signals to processes (often to terminate them), see L<perlfunc/kill>.
=item labs
=item setgid
-Sets the real group identifier for this process.
-Identical to assigning a value to the Perl's builtin C<$)> variable,
-see L<perlvar/$UID>.
+Sets the real group identifier and the effective group identifier for
+this process. Similar to assigning a value to the Perl's builtin
+C<$)> variable, see L<perlvar/$GID>, except that the latter
+will change only the real user identifier, and that the setgid()
+uses only a single numeric argument, as opposed to a space-separated
+list of numbers.
=item setjmp
The following will set the LC_CTYPE behaviour according to the locale
environment variables (the second argument C<"">).
-Please see your systems L<setlocale(3)> documentation for the locale
+Please see your systems C<setlocale(3)> documentation for the locale
environment variables' meaning or consult L<perllocale>.
$loc = setlocale( LC_CTYPE, "" );
=item setuid
-Sets the real user identifier for this process.
-Identical to assigning a value to the Perl's builtin C<$E<lt>> variable,
-see L<perlvar/$UID>.
+Sets the real user identifier and the effective user identifier for
+this process. Similar to assigning a value to the Perl's builtin
+C<$E<lt>> variable, see L<perlvar/$UID>, except that the latter
+will change only the real user identifier.
=item sigaction
This is identical to Perl's builtin C<sin()> function
for returning the sine of the numerical argument,
-see L<perlfunc/sin>.
+see L<perlfunc/sin>. See also L<Math::Trig>.
=item sinh
This is identical to the C function C<sinh()>
for returning the hyperbolic sine of the numerical argument.
+See also L<Math::Trig>.
=item sleep
=item tan
This is identical to the C function C<tan()>, returning the
-tangent of the numerical argument.
+tangent of the numerical argument. See also L<Math::Trig>.
=item tanh
This is identical to the C function C<tanh()>, returning the
-hyperbolic tangent of the numerical argument.
+hyperbolic tangent of the numerical argument. See also L<Math::Trig>.
=item tcdrain
$tmpfile = POSIX::tmpnam();
-See also L<File::Temp>.
+For security reasons, which are probably detailed in your system's
+documentation for the C library tmpnam() function, this interface
+should not be used; instead see L<File::Temp>.
=item tolower
Wait for a child process to change state. This is identical to Perl's
builtin C<waitpid()> function, see L<perlfunc/waitpid>.
- $pid = POSIX::waitpid( -1, &POSIX::WNOHANG );
+ $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
print "status = ", ($? / 256), "\n";
=item wcstombs
WNOHANG WUNTRACED
+=over 16
+
+=item WNOHANG
+
+Do not suspend the calling process until a child process
+changes state but instead return immediately.
+
+=item WUNTRACED
+
+Catch stopped child processes.
+
+=back
+
=item Macros
WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIFSTOPPED WSTOPSIG
+=over 16
+
+=item WIFEXITED
+
+WIFEXITED($?) returns true if the child process exited normally
+(C<exit()> or by falling off the end of C<main()>)
+
+=item WEXITSTATUS
+
+WEXITSTATUS($?) returns the normal exit status of the child process
+(only meaningful if WIFEXITED($?) is true)
+
+=item WIFSIGNALED
+
+WIFSIGNALED($?) returns true if the child process terminated because
+of a signal
+
+=item WTERMSIG
+
+WTERMSIG($?) returns the signal the child process terminated for
+(only meaningful if WIFSIGNALED($?) is true)
+
+=item WIFSTOPPED
+
+WIFSTOPPED($?) returns true if the child process is currently stopped
+(can happen only if you specified the WUNTRACED flag to waitpid())
+
+=item WSTOPSIG
+
+WSTOPSIG($?) returns the signal the child process was stopped for
+(only meaningful if WIFSTOPPED($?) is true)
+
+=back
+
=back