The POSIX module permits you to access all (or nearly all) the standard
POSIX 1003.1 identifiers. Many of these identifiers have been given Perl-ish
-interfaces. Things which are C<#defines> in C, like EINTR or O_NDELAY, are
-automatically exported into your namespace. All functions are only exported
-if you ask for them explicitly. Most likely people will prefer to use the
-fully-qualified function names.
+interfaces.
+
+I<Everything is exported by default> with the exception of any POSIX
+functions with the same name as a built-in Perl function, such as
+C<abs>, C<alarm>, C<rmdir>, C<write>, etc.., which will be exported
+only if you ask for them explicitly. This is an unfortunate backwards
+compatibility feature. You can stop the exporting by saying C<use
+POSIX ()> and then use the fully qualified names (ie. C<POSIX::SEEK_END>).
This document gives a condensed list of the features available in the POSIX
module. Consult your operating system's manpages for general information on
This is identical to the C function C<_exit()>. It exits the program
immediately which means among other things buffered I/O is B<not> flushed.
+Note that when using threads and in Linux this is B<not> a good way to
+exit a thread because in Linux processes and threads are kind of the
+same thing (Note: while this is the situation in early 2003 there are
+projects under way to have threads with more POSIXly semantics in Linux).
+If you want not to return from a thread, detach the thread.
+
=item abort
This is identical to the C function C<abort()>. It terminates the
=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 the C function C<fmod()>.
- $r = modf($x, $y);
+ $r = fmod($x, $y);
It returns the remainder C<$r = $x - $n*$y>, where C<$n = trunc($x/$y)>.
The C<$r> has the same sign as C<$x> and magnitude (absolute value)
uses file descriptors such as those obtained by calling C<POSIX::open>.
The following will determine the maximum length of the longest allowable
-pathname on the filesystem which holds C</tmp/foo>.
+pathname on the filesystem which holds C</var/foo>.
- $fd = POSIX::open( "/tmp/foo", &POSIX::O_RDONLY );
+ $fd = POSIX::open( "/var/foo", &POSIX::O_RDONLY );
$path_max = POSIX::fpathconf( $fd, &POSIX::_PC_PATH_MAX );
Returns C<undef> on failure.
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
@stats = POSIX::fstat( $fd );
+=item fsync
+
+Use method C<IO::Handle::sync()> instead.
+
=item ftell
Use method C<IO::Seekable::tell()> instead, or see L<perlfunc/tell>.
=item isalnum
-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.
+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 C<isalnum>. Does not work on
+Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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.
+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 C<isalpha>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the C</[[:alpha:]]/> construct instead.
=item isatty
=item iscntrl
-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.
+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 C<iscntrl>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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.
+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 C<isdigit> (unlikely, but
+still possible). Does not work on Unicode characters code point 256
+or higher. Consider using regular expressions and the 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.
+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 C<isgraph>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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/>.
+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 C<islower>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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.
+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 C<isprint>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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.
+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 C<ispunct>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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.
+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 C<isspace>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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/>.
+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 C<isupper>. Does not work
+on Unicode characters code point 256 or higher. Consider using regular
+expressions and the 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>.
+character or to a whole string. Note that locale settings may affect what
+characters are considered C<isxdigit> (unlikely, but still possible).
+Does not work on Unicode characters code point 256 or higher.
+Consider using regular expressions and the C</[[:xdigit:]]/>
+construct instead, or simply C</[0-9a-f]/i>.
=item kill
Open a directory for reading.
- $dir = POSIX::opendir( "/tmp" );
+ $dir = POSIX::opendir( "/var" );
@files = POSIX::readdir( $dir );
POSIX::closedir( $dir );
Retrieves the value of a configurable limit on a file or directory.
The following will determine the maximum length of the longest allowable
-pathname on the filesystem which holds C</tmp>.
+pathname on the filesystem which holds C</var>.
- $path_max = POSIX::pathconf( "/tmp", &POSIX::_PC_PATH_MAX );
+ $path_max = POSIX::pathconf( "/var", &POSIX::_PC_PATH_MAX );
Returns C<undef> on failure.
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, "" );
Synopsis:
- sigaction(sig, action, oldaction = 0)
+ sigaction(signal, action, oldaction = 0)
-Returns C<undef> on failure.
+Returns C<undef> on failure. The C<signal> must be a number (like
+SIGHUP), not a string (like "SIGHUP"), though Perl does try hard
+to understand you.
=item siglongjmp
=item sleep
-This is identical to Perl's builtin C<sleep()> function
-for suspending the execution of the current for process
-for certain number of seconds, see L<perlfunc/sleep>.
+This is functionally identical to Perl's builtin C<sleep()> function
+for suspending the execution of the current for process for certain
+number of seconds, see L<perlfunc/sleep>. There is one significant
+difference, however: C<POSIX::sleep()> returns the number of
+B<unslept> seconds, while the C<CORE::sleep()> returns the
+number of slept seconds.
=item sprintf
year (C<year>) is given in years since 1900. I.e., the year 1995 is 95; the
year 2001 is 101. Consult your system's C<strftime()> manpage for details
about these and the other arguments.
+
If you want your code to be portable, your format (C<fmt>) argument
should use only the conversion specifiers defined by the ANSI C
-standard. These are C<aAbBcdHIjmMpSUwWxXyYZ%>.
-The given arguments are made consistent
-as though by calling C<mktime()> before calling your system's
-C<strftime()> function, except that the C<isdst> value is not affected.
+standard (C89, to play safe). These are C<aAbBcdHIjmMpSUwWxXyYZ%>.
+But even then, the B<results> of some of the conversion specifiers are
+non-portable. For example, the specifiers C<aAbBcpZ> 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 C<c> changes according to the timezone settings of the
+user and the timezone computation rules of the operating system.
+The C<Z> specifier is notoriously unportable since the names of
+timezones are non-standard. Sticking to the numeric specifiers is the
+safest route.
+
+The given arguments are made consistent as though by calling
+C<mktime()> before calling your system's C<strftime()> function,
+except that the C<isdst> value is not affected.
The string for Tuesday, December 12, 1995.
=item tcflush
This is similar to the C function C<tcflush()> for flushing
-the I/O buffers of its argumeny stream.
+the I/O buffers of its argument stream.
Returns C<undef> on failure.
$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
C<sa_flags>, it defaults to 0.
$sigset = POSIX::SigSet->new(SIGINT, SIGQUIT);
- $sigaction = POSIX::SigAction->new( 'main::handler', $sigset, &POSIX::SA_NOCLDSTOP );
+ $sigaction = POSIX::SigAction->new( \&main::handler, $sigset, &POSIX::SA_NOCLDSTOP );
-This C<POSIX::SigAction> object
should be used with the C<POSIX::sigaction()>
+This C<POSIX::SigAction> object
is intended for use with the C<POSIX::sigaction()>
function.
=back
+=over 8
+
+=item handler
+
+=item mask
+
+=item flags
+
+accessor functions to get/set the values of a SigAction object.
+
+ $sigset = $sigaction->mask;
+ $sigaction->flags(&POSIX::SA_RESTART);
+
+=item safe
+
+accessor function for the "safe signals" flag of a SigAction object; see
+L<perlipc> for general information on safe (a.k.a. "deferred") signals. If
+you wish to handle a signal safely, use this accessor to set the "safe" flag
+in the C<POSIX::SigAction> object:
+
+ $sigaction->safe(1);
+
+You may also examine the "safe" flag on the output action object which is
+filled in when given as the third parameter to C<POSIX::sigaction()>:
+
+ sigaction(SIGINT, $new_action, $old_action);
+ if ($old_action->safe) {
+ # previous SIGINT handler used safe signals
+ }
+
+=back
+
=head2 POSIX::SigSet
=over 8
=item Constants
-_SC_ARG_MAX _SC_CHILD_MAX _SC_CLK_TCK _SC_JOB_CONTROL _SC_NGROUPS_MAX _SC_OPEN_MAX _SC_SAVED_IDS _SC_STREAM_MAX _SC_TZNAME_MAX _SC_VERSION
+_SC_ARG_MAX _SC_CHILD_MAX _SC_CLK_TCK _SC_JOB_CONTROL _SC_NGROUPS_MAX _SC_OPEN_MAX _SC_PAGESIZE _SC_SAVED_IDS _SC_STREAM_MAX _SC_TZNAME_MAX _SC_VERSION
=back
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
https://perl5.git.perl.org / perl5.git / blobdiff