POSIX - Perl interface to IEEE Std 1003.1
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.
Everything is exported by default with the exception of any POSIX
functions with the same name as a built-in Perl function, such as
abs, alarm, rmdir, 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 use
POSIX ()
and then use the fully qualified names (ie. 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 most features. Consult perlfunc for functions which are noted as being identical to Perl's builtin functions.
The first section describes POSIX functions from the 1003.1 specification. The second section describes some classes for signal objects, TTY objects, and other miscellaneous objects. The remaining sections list various constants and macros in an organization which roughly follows IEEE Std 1003.1b-1993.
The POSIX module is probably the most complex Perl module supplied with the standard distribution. It incorporates autoloading, namespace games, and dynamic loading of code that's in Perl, C, or both. It's a great source of wisdom.
A few functions are not implemented because they are C specific. If you attempt to call these, they will print a message telling you that they aren't implemented, and suggest using the Perl equivalent should one exist. For example, trying to access the setjmp() call will elicit the message "setjmp() is C-specific: use eval {} instead".
Furthermore, some evil vendors will claim 1003.1 compliance, but in fact are not so: they will not pass the PCTS (POSIX Compliance Test Suites). For example, one vendor may not define EDEADLK, or the semantics of the errno values set by open(2) might not be quite right. Perl does not attempt to verify POSIX compliance. That means you can currently successfully say "use POSIX", and then later in your program you find that your vendor has been lax and there's no usable ICANON macro after all. This could be construed to be a bug.
This is identical to the C function _exit()
. It exits the program
immediately which means among other things buffered I/O is not flushed.
Note that when using threads and in Linux this is 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.
This is identical to the C function abort()
. It terminates the
process with a SIGABRT
signal unless caught by a signal handler or
if the handler does not return normally (it e.g. does a longjmp
).
This is identical to Perl's builtin abs() function, returning
the absolute value of its numerical argument.
Determines the accessibility of a file.
- if( POSIX::access( "/", &POSIX::R_OK ) ){
- print "have read permission\n";
- }
Returns undef on failure. Note: do not use access()
for
security purposes. Between the access()
call and the operation
you are preparing for the permissions might change: a classic
race condition.
This is identical to the C function acos()
, returning
the arcus cosine of its numerical argument. See also Math::Trig.
This is identical to Perl's builtin alarm() function,
either for arming or disarming the SIGARLM
timer.
This is identical to the C function asctime()
. It returns
a string of the form
- "Fri Jun 2 18:22:13 2000\n\0"
and it is called thusly
- $asctime = asctime($sec, $min, $hour, $mday, $mon, $year,
- $wday, $yday, $isdst);
The $mon
is zero-based: January equals 0
. The $year
is
1900-based: 2001 equals 101
. $wday
and $yday
default to zero
(and are usually ignored anyway), and $isdst
defaults to -1.
This is identical to the C function asin()
, returning
the arcus sine of its numerical argument. See also Math::Trig.
Unimplemented, but you can use die and the Carp module to achieve similar things.
This is identical to the C function atan()
, returning the
arcus tangent of its numerical argument. See also Math::Trig.
This is identical to Perl's builtin atan2() function, returning
the arcus tangent defined by its two numerical arguments, the y
coordinate and the x coordinate. See also Math::Trig.
atexit() is C-specific: use END {}
instead, see perlsub.
atof() is C-specific. Perl converts strings to numbers transparently. If you need to force a scalar to a number, add a zero to it.
atoi() is C-specific. Perl converts strings to numbers transparently. If you need to force a scalar to a number, add a zero to it. If you need to have just the integer part, see int.
atol() is C-specific. Perl converts strings to numbers transparently. If you need to force a scalar to a number, add a zero to it. If you need to have just the integer part, see int.
bsearch() not supplied. For doing binary search on wordlists, see Search::Dict.
calloc() is C-specific. Perl does memory management transparently.
This is identical to the C function ceil()
, returning the smallest
integer value greater than or equal to the given numerical argument.
This is identical to Perl's builtin chdir() function, allowing
one to change the working (default) directory, see chdir.
This is identical to Perl's builtin chmod() function, allowing
one to change file and directory permissions, see chmod.
This is identical to Perl's builtin chown() function, allowing one
to change file and directory owners and groups, see chown.
Use the method IO::Handle::clearerr()
instead, to reset the error
state (if any) and EOF state (if any) of the given stream.
This is identical to the C function clock()
, returning the
amount of spent processor time in microseconds.
Close the file. This uses file descriptors such as those obtained by calling
POSIX::open
.
- $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
- POSIX::close( $fd );
Returns undef on failure.
See also close.
This is identical to Perl's builtin closedir() function for closing
a directory handle, see closedir.
This is identical to Perl's builtin cos() function, for returning
the cosine of its numerical argument, see cos.
See also Math::Trig.
This is identical to the C function cosh()
, for returning
the hyperbolic cosine of its numeric argument. See also Math::Trig.
Create a new file. This returns a file descriptor like the ones returned by
POSIX::open
. Use POSIX::close
to close the file.
- $fd = POSIX::creat( "foo", 0611 );
- POSIX::close( $fd );
See also sysopen and its O_CREAT
flag.
Generates the path name for the controlling terminal.
- $path = POSIX::ctermid();
This is identical to the C function ctime()
and equivalent
to asctime(localtime(...))
, see asctime and localtime.
Get the login name of the owner of the current process.
- $name = POSIX::cuserid();
This is identical to the C function difftime()
, for returning
the time difference (in seconds) between two times (as returned
by time()), see time.
div() is C-specific, use int on the usual / division and
the modulus %
.
This is similar to the C function dup()
, for duplicating a file
descriptor.
This uses file descriptors such as those obtained by calling
POSIX::open
.
Returns undef on failure.
This is similar to the C function dup2()
, for duplicating a file
descriptor to an another known file descriptor.
This uses file descriptors such as those obtained by calling
POSIX::open
.
Returns undef on failure.
Returns the value of errno.
- $errno = POSIX::errno();
This identical to the numerical values of the $!
, see $ERRNO in perlvar.
execl() is C-specific, see exec.
execle() is C-specific, see exec.
execlp() is C-specific, see exec.
execv() is C-specific, see exec.
execve() is C-specific, see exec.
execvp() is C-specific, see exec.
This is identical to Perl's builtin exit() function for exiting the
program, see exit.
This is identical to Perl's builtin exp() function for
returning the exponent (e-based) of the numerical argument,
see exp.
This is identical to Perl's builtin abs() function for returning
the absolute value of the numerical argument, see abs.
Use method IO::Handle::close()
instead, or see close.
This is identical to Perl's builtin fcntl() function,
see fcntl.
Use method IO::Handle::new_from_fd()
instead, or see open.
Use method IO::Handle::eof()
instead, or see eof.
Use method IO::Handle::error()
instead.
Use method IO::Handle::flush()
instead.
See also $OUTPUT_AUTOFLUSH in perlvar.
Use method IO::Handle::getc()
instead, or see read.
Use method IO::Seekable::getpos()
instead, or see seek in L.
Use method IO::Handle::gets()
instead. Similar to <>, also known
as readline.
Use method IO::Handle::fileno()
instead, or see fileno.
This is identical to the C function floor()
, returning the largest
integer value less than or equal to the numerical argument.
This is identical to the C function fmod()
.
- $r = fmod($x, $y);
It returns the remainder $r = $x - $n*$y
, where $n = trunc($x/$y)
.
The $r
has the same sign as $x
and magnitude (absolute value)
less than the magnitude of $y
.
Use method IO::File::open()
instead, or see open.
This is identical to Perl's builtin fork() function
for duplicating the current process, see fork
and perlfork if you are in Windows.
Retrieves the value of a configurable limit on a file or directory. This
uses file descriptors such as those obtained by calling POSIX::open
.
The following will determine the maximum length of the longest allowable
pathname on the filesystem which holds /var/foo.
- $fd = POSIX::open( "/var/foo", &POSIX::O_RDONLY );
- $path_max = POSIX::fpathconf( $fd, &POSIX::_PC_PATH_MAX );
Returns undef on failure.
fprintf() is C-specific, see printf instead.
fputc() is C-specific, see print instead.
fputs() is C-specific, see print instead.
fread() is C-specific, see read instead.
free() is C-specific. Perl does memory management transparently.
freopen() is C-specific, see open instead.
Return the mantissa and exponent of a floating-point number.
- ($mantissa, $exponent) = POSIX::frexp( 1.234e56 );
fscanf() is C-specific, use <> and regular expressions instead.
Use method IO::Seekable::seek()
instead, or see seek.
Use method IO::Seekable::setpos()
instead, or seek seek.
Get file status. This uses file descriptors such as those obtained by
calling POSIX::open
. The data returned is identical to the data from
Perl's builtin stat function.
- $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
- @stats = POSIX::fstat( $fd );
Use method IO::Handle::sync()
instead.
Use method IO::Seekable::tell()
instead, or see tell.
fwrite() is C-specific, see print instead.
This is identical to Perl's builtin getc() function,
see getc.
Returns one character from STDIN. Identical to Perl's getc(),
see getc.
Returns the name of the current working directory. See also Cwd.
Returns the effective group identifier. Similar to Perl' s builtin
variable $(
, see $EGID in perlvar.
Returns the value of the specified environment variable.
The same information is available through the %ENV
array.
Returns the effective user identifier. Identical to Perl's builtin $>
variable, see $EUID in perlvar.
Returns the user's real group identifier. Similar to Perl's builtin
variable $)
, see $GID in perlvar.
This is identical to Perl's builtin getgrgid() function for
returning group entries by group identifiers, see
getgrgid.
This is identical to Perl's builtin getgrnam() function for
returning group entries by group names, see getgrnam.
Returns the ids of the user's supplementary groups. Similar to Perl's
builtin variable $)
, see $GID in perlvar.
This is identical to Perl's builtin getlogin() function for
returning the user name associated with the current session, see
getlogin.
This is identical to Perl's builtin getpgrp() function for
returning the process group identifier of the current process, see
getpgrp.
Returns the process identifier. Identical to Perl's builtin
variable $$
, see $PID in perlvar.
This is identical to Perl's builtin getppid() function for
returning the process identifier of the parent process of the current
process , see getppid.
This is identical to Perl's builtin getpwnam() function for
returning user entries by user names, see getpwnam.
This is identical to Perl's builtin getpwuid() function for
returning user entries by user identifiers, see getpwuid.
Returns one line from STDIN
, similar to <>, also known
as the readline() function, see readline.
NOTE: if you have C programs that still use gets()
, be very
afraid. The gets()
function is a source of endless grief because
it has no buffer overrun checks. It should never be used. The
fgets()
function should be preferred instead.
Returns the user's identifier. Identical to Perl's builtin $<
variable,
see $UID in perlvar.
This is identical to Perl's builtin gmtime() function for
converting seconds since the epoch to a date in Greenwich Mean Time,
see gmtime.
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 isalnum
. Does not work on
Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:alnum:]]/
construct instead, or possibly
the /\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 isalpha
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:alpha:]]/
construct instead.
Returns a boolean indicating whether the specified filehandle is connected
to a tty. Similar to the -t
operator, see -X.
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 iscntrl
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:cntrl:]]/
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 isdigit
(unlikely, but
still possible). Does not work on Unicode characters code point 256
or higher. Consider using regular expressions and the /[[:digit:]]/
construct instead, or the /\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 isgraph
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:graph:]]/
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 islower
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:lower:]]/
construct instead. Do not use
/[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 isprint
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:print:]]/
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 ispunct
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:punct:]]/
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 isspace
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:space:]]/
construct instead, or the /\s/
construct. (Note that /\s/
and /[[:space:]]/
are slightly
different in that /[[:space:]]/
can normally match a vertical tab,
while /\s/
does not.)
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 isupper
. Does not work
on Unicode characters code point 256 or higher. Consider using regular
expressions and the /[[:upper:]]/
construct instead. Do not use
/[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 isxdigit
(unlikely, but still possible).
Does not work on Unicode characters code point 256 or higher.
Consider using regular expressions and the /[[:xdigit:]]/
construct instead, or simply /[0-9a-f]/i
.
This is identical to Perl's builtin kill() function for sending
signals to processes (often to terminate them), see kill.
(For returning absolute values of long integers.) labs() is C-specific, see abs instead.
This is identical to the C function ldexp()
for multiplying floating point numbers with powers of two.
- $x_quadrupled = POSIX::ldexp($x, 2);
(For computing dividends of long integers.)
ldiv() is C-specific, use / and int() instead.
This is identical to Perl's builtin link() function
for creating hard links into files, see link.
Get numeric formatting information. Returns a reference to a hash containing the current locale formatting values.
Here is how to query the database for the de (Deutsch or German) locale.
- $loc = POSIX::setlocale( &POSIX::LC_ALL, "de" );
- print "Locale = $loc\n";
- $lconv = POSIX::localeconv();
- print "decimal_point = ", $lconv->{decimal_point}, "\n";
- print "thousands_sep = ", $lconv->{thousands_sep}, "\n";
- print "grouping = ", $lconv->{grouping}, "\n";
- print "int_curr_symbol = ", $lconv->{int_curr_symbol}, "\n";
- print "currency_symbol = ", $lconv->{currency_symbol}, "\n";
- print "mon_decimal_point = ", $lconv->{mon_decimal_point}, "\n";
- print "mon_thousands_sep = ", $lconv->{mon_thousands_sep}, "\n";
- print "mon_grouping = ", $lconv->{mon_grouping}, "\n";
- print "positive_sign = ", $lconv->{positive_sign}, "\n";
- print "negative_sign = ", $lconv->{negative_sign}, "\n";
- print "int_frac_digits = ", $lconv->{int_frac_digits}, "\n";
- print "frac_digits = ", $lconv->{frac_digits}, "\n";
- print "p_cs_precedes = ", $lconv->{p_cs_precedes}, "\n";
- print "p_sep_by_space = ", $lconv->{p_sep_by_space}, "\n";
- print "n_cs_precedes = ", $lconv->{n_cs_precedes}, "\n";
- print "n_sep_by_space = ", $lconv->{n_sep_by_space}, "\n";
- print "p_sign_posn = ", $lconv->{p_sign_posn}, "\n";
- print "n_sign_posn = ", $lconv->{n_sign_posn}, "\n";
This is identical to Perl's builtin localtime() function for
converting seconds since the epoch to a date see localtime.
This is identical to Perl's builtin log() function,
returning the natural (e-based) logarithm of the numerical argument,
see log.
This is identical to the C function log10()
,
returning the 10-base logarithm of the numerical argument.
You can also use
or
- sub log10 { log($_[0]) / 2.30258509299405 }
or
- sub log10 { log($_[0]) * 0.434294481903252 }
longjmp() is C-specific: use die instead.
Move the file's read/write position. This uses file descriptors such as
those obtained by calling POSIX::open
.
- $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
- $off_t = POSIX::lseek( $fd, 0, &POSIX::SEEK_SET );
Returns undef on failure.
malloc() is C-specific. Perl does memory management transparently.
This is identical to the C function mblen()
.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
This is identical to the C function mbstowcs()
.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
This is identical to the C function mbtowc()
.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
memchr() is C-specific, see index instead.
memcmp() is C-specific, use eq
instead, see perlop.
memset() is C-specific, use x
instead, see perlop.
This is identical to Perl's builtin mkdir() function
for creating directories, see mkdir.
This is similar to the C function mkfifo()
for creating
FIFO special files.
- if (mkfifo($path, $mode)) { ....
Returns undef on failure. The $mode
is similar to the
mode of mkdir(), see mkdir, though for mkfifo
you must specify the $mode
.
Convert date/time info to a calendar time.
Synopsis:
- mktime(sec, min, hour, mday, mon, year, wday = 0, yday = 0, isdst = -1)
The month (mon
), weekday (wday
), and yearday (yday
) begin at zero.
I.e. January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1. The
year (year
) is given in years since 1900. I.e. The year 1995 is 95; the
year 2001 is 101. Consult your system's mktime()
manpage for details
about these and the other arguments.
Calendar time for December 12, 1995, at 10:30 am.
- $time_t = POSIX::mktime( 0, 30, 10, 12, 11, 95 );
- print "Date = ", POSIX::ctime($time_t);
Returns undef on failure.
Return the integral and fractional parts of a floating-point number.
- ($fractional, $integral) = POSIX::modf( 3.14 );
This is similar to the C function nice()
, 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.
Returns undef on failure.
offsetof() is C-specific, you probably want to see pack instead.
Open a file for reading for writing. This returns file descriptors, not
Perl filehandles. Use POSIX::close
to close the file.
Open a file read-only with mode 0666.
- $fd = POSIX::open( "foo" );
Open a file for read and write.
- $fd = POSIX::open( "foo", &POSIX::O_RDWR );
Open a file for write, with truncation.
- $fd = POSIX::open( "foo", &POSIX::O_WRONLY | &POSIX::O_TRUNC );
Create a new file with mode 0640. Set up the file for writing.
- $fd = POSIX::open( "foo", &POSIX::O_CREAT | &POSIX::O_WRONLY, 0640 );
Returns undef on failure.
See also sysopen.
Open a directory for reading.
- $dir = POSIX::opendir( "/var" );
- @files = POSIX::readdir( $dir );
- POSIX::closedir( $dir );
Returns undef on failure.
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 /var.
- $path_max = POSIX::pathconf( "/var", &POSIX::_PC_PATH_MAX );
Returns undef on failure.
This is similar to the C function pause()
, which suspends
the execution of the current process until a signal is received.
Returns undef on failure.
This is identical to the C function perror()
, which outputs to the
standard error stream the specified message followed by ": " and the
current error string. Use the warn() function and the $!
variable instead, see warn and $ERRNO in perlvar.
Create an interprocess channel. This returns file descriptors like those
returned by POSIX::open
.
- my ($read, $write) = POSIX::pipe();
- POSIX::write( $write, "hello", 5 );
- POSIX::read( $read, $buf, 5 );
See also pipe.
Computes $x
raised to the power $exponent
.
- $ret = POSIX::pow( $x, $exponent );
You can also use the **
operator, see perlop.
Formats and prints the specified arguments to STDOUT. See also printf.
putc() is C-specific, see print instead.
putchar() is C-specific, see print instead.
puts() is C-specific, see print instead.
qsort() is C-specific, see sort instead.
Sends the specified signal to the current process.
See also kill and the $$
in $PID in perlvar.
Read from a file. This uses file descriptors such as those obtained by
calling POSIX::open
. If the buffer $buf
is not large enough for the
read then Perl will extend it to make room for the request.
- $fd = POSIX::open( "foo", &POSIX::O_RDONLY );
- $bytes = POSIX::read( $fd, $buf, 3 );
Returns undef on failure.
See also sysread.
This is identical to Perl's builtin readdir() function
for reading directory entries, see readdir.
realloc() is C-specific. Perl does memory management transparently.
This is identical to Perl's builtin unlink() function
for removing files, see unlink.
This is identical to Perl's builtin rename() function
for renaming files, see rename.
Seeks to the beginning of the file.
This is identical to Perl's builtin rewinddir() function for
rewinding directory entry streams, see rewinddir.
This is identical to Perl's builtin rmdir() function
for removing (empty) directories, see rmdir.
scanf() is C-specific, use <> and regular expressions instead, see perlre.
Sets the real group identifier and the effective group identifier for
this process. Similar to assigning a value to the Perl's builtin
$)
variable, see $EGID in perlvar, 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.
Modifies and queries program's locale. The following examples assume
- use POSIX qw(setlocale LC_ALL LC_CTYPE);
has been issued.
The following will set the traditional UNIX system locale behavior
(the second argument "C"
).
- $loc = setlocale( LC_ALL, "C" );
The following will query the current LC_CTYPE category. (No second argument means 'query'.)
- $loc = setlocale( LC_CTYPE );
The following will set the LC_CTYPE behaviour according to the locale
environment variables (the second argument ""
).
Please see your systems setlocale(3)
documentation for the locale
environment variables' meaning or consult perllocale.
- $loc = setlocale( LC_CTYPE, "" );
The following will set the LC_COLLATE behaviour to Argentinian Spanish. NOTE: 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.
- $loc = setlocale( LC_ALL, "es_AR.ISO8859-1" );
This is similar to the C function setpgid()
for
setting the process group identifier of the current process.
Returns undef on failure.
This is identical to the C function setsid()
for
setting the session identifier of the current process.
Sets the real user identifier and the effective user identifier for
this process. Similar to assigning a value to the Perl's builtin
$<
variable, see $UID in perlvar, except that the latter
will change only the real user identifier.
Detailed signal management. This uses POSIX::SigAction
objects for
the action
and oldaction
arguments (the oldaction can also be
just a hash reference). Consult your system's sigaction
manpage
for details, see also POSIX::SigRt
.
Synopsis:
- sigaction(signal, action, oldaction = 0)
Returns undef on failure. The signal
must be a number (like
SIGHUP), not a string (like "SIGHUP"), though Perl does try hard
to understand you.
If you use the SA_SIGINFO 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:
- 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
The following are also defined by POSIX/SUSv3, but unfortunately not very widely implemented:
- 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
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 unpack() them from.
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
sigaction
and possibly also siginfo
documentation.
siglongjmp() is C-specific: use die instead.
Examine signals that are blocked and pending. This uses POSIX::SigSet
objects for the sigset
argument. Consult your system's sigpending
manpage for details.
Synopsis:
- sigpending(sigset)
Returns undef on failure.
Change and/or examine calling process's signal mask. This uses
POSIX::SigSet
objects for the sigset
and oldsigset
arguments.
Consult your system's sigprocmask
manpage for details.
Synopsis:
- sigprocmask(how, sigset, oldsigset = 0)
Returns undef on failure.
Install a signal mask and suspend process until signal arrives. This uses
POSIX::SigSet
objects for the signal_mask
argument. Consult your
system's sigsuspend
manpage for details.
Synopsis:
- sigsuspend(signal_mask)
Returns undef on failure.
This is identical to Perl's builtin sin() function
for returning the sine of the numerical argument,
see sin. See also Math::Trig.
This is identical to the C function sinh()
for returning the hyperbolic sine of the numerical argument.
See also Math::Trig.
This is functionally identical to Perl's builtin sleep() function
for suspending the execution of the current for process for certain
number of seconds, see sleep. There is one significant
difference, however: POSIX::sleep()
returns the number of
unslept seconds, while the CORE::sleep()
returns the
number of slept seconds.
This is similar to Perl's builtin sprintf() function
for returning a string that has the arguments formatted as requested,
see sprintf.
This is identical to Perl's builtin sqrt() function.
for returning the square root of the numerical argument,
see sqrt.
Give a seed the pseudorandom number generator, see srand.
sscanf() is C-specific, use regular expressions instead, see perlre.
This is identical to Perl's builtin stat() function
for returning information about files and directories.
strcat() is C-specific, use .=
instead, see perlop.
strchr() is C-specific, see index instead.
strcmp() is C-specific, use eq
or cmp
instead, see perlop.
This is identical to the C function strcoll()
for collating (comparing) strings transformed using
the strxfrm()
function. Not really needed since
Perl can do this transparently, see perllocale.
strcpy() is C-specific, use =
instead, see perlop.
strcspn() is C-specific, use regular expressions instead, see perlre.
Returns the error string for the specified errno.
Identical to the string form of the $!
, see $ERRNO in perlvar.
Convert date and time information to string. Returns the string.
Synopsis:
- strftime(fmt, sec, min, hour, mday, mon, year, wday = -1, yday = -1, isdst = -1)
The month (mon
), weekday (wday
), and yearday (yday
) begin at zero.
I.e. January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1. The
year (year
) is given in years since 1900. I.e., the year 1995 is 95; the
year 2001 is 101. Consult your system's strftime()
manpage for details
about these and the other arguments.
If you want your code to be portable, your format (fmt
) argument
should use only the conversion specifiers defined by the ANSI C
standard (C89, to play safe). These are aAbBcdHIjmMpSUwWxXyYZ%
.
But even then, the results of some of the conversion specifiers are
non-portable. For example, the specifiers 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
changes according to the timezone settings of the
user and the timezone computation rules of the operating system.
The 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
mktime()
before calling your system's strftime()
function,
except that the isdst
value is not affected.
The string for Tuesday, December 12, 1995.
- $str = POSIX::strftime( "%A, %B %d, %Y", 0, 0, 0, 12, 11, 95, 2 );
- print "$str\n";
strncat() is C-specific, use .=
instead, see perlop.
strncmp() is C-specific, use eq
instead, see perlop.
strncpy() is C-specific, use =
instead, see perlop.
strpbrk() is C-specific, use regular expressions instead, see perlre.
strrchr() is C-specific, see rindex instead.
strspn() is C-specific, use regular expressions instead, see perlre.
This is identical to Perl's builtin index() function,
see index.
String to double 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 strtod. However, non-POSIX systems may not check for overflow, and therefore will never set $!.
strtod should respect any POSIX setlocale() settings.
To parse a string $str as a floating point number use
- $! = 0;
- ($num, $n_unparsed) = POSIX::strtod($str);
The second returned item and $! can be used to check for valid input:
- if (($str eq '') || ($n_unparsed != 0) || $!) {
- die "Non-numeric input $str" . ($! ? ": $!\n" : "\n");
- }
When called in a scalar context strtod returns the parsed number.
strtok() is C-specific, use regular expressions instead, see perlre, or split.
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 $!.
strtol should respect any POSIX setlocale() settings.
To parse a string $str as a number in some base $base use
- $! = 0;
- ($num, $n_unparsed) = POSIX::strtol($str, $base);
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 "0x" or "0X" means hexadecimal; a leading "0" means octal; any other leading characters mean decimal. Thus, "1234" is parsed as a decimal number, "01234" as an octal number, and "0x1234" as a hexadecimal number.
The second returned item and $! can be used to check for valid input:
- if (($str eq '') || ($n_unparsed != 0) || !$!) {
- die "Non-numeric input $str" . $! ? ": $!\n" : "\n";
- }
When called in a scalar context strtol returns the parsed number.
String to unsigned (long) integer translation. strtoul() is identical to strtol() except that strtoul() only parses unsigned integers. See strtol for details.
Note: Some vendors supply strtod() and strtol() but not strtoul(). Other vendors that do supply strtoul() parse "-1" as a valid value.
String transformation. Returns the transformed string.
- $dst = POSIX::strxfrm( $src );
Used in conjunction with the strcoll()
function, see strcoll.
Not really needed since Perl can do this transparently, see perllocale.
Retrieves values of system configurable variables.
The following will get the machine's clock speed.
- $clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );
Returns undef on failure.
This is identical to Perl's builtin system() function, see
system.
This is identical to the C function tan()
, returning the
tangent of the numerical argument. See also Math::Trig.
This is identical to the C function tanh()
, returning the
hyperbolic tangent of the numerical argument. See also Math::Trig.
This is similar to the C function tcdrain()
for draining
the output queue of its argument stream.
Returns undef on failure.
This is similar to the C function tcflow()
for controlling
the flow of its argument stream.
Returns undef on failure.
This is similar to the C function tcflush()
for flushing
the I/O buffers of its argument stream.
Returns undef on failure.
This is identical to the C function tcgetpgrp()
for returning the
process group identifier of the foreground process group of the controlling
terminal.
This is similar to the C function tcsendbreak()
for sending
a break on its argument stream.
Returns undef on failure.
This is similar to the C function tcsetpgrp()
for setting the
process group identifier of the foreground process group of the controlling
terminal.
Returns undef on failure.
This is identical to Perl's builtin time() function
for returning the number of seconds since the epoch
(whatever it is for the system), see time.
The times() function returns elapsed realtime since some point in the past (such as system startup), user and system times for this process, and user and system times used by child processes. All times are returned in clock ticks.
- ($realtime, $user, $system, $cuser, $csystem) = POSIX::times();
Note: Perl's builtin times() function returns four values, measured in
seconds.
Use method IO::File::new_tmpfile()
instead, or see File::Temp.
Returns a name for a temporary file.
- $tmpfile = POSIX::tmpnam();
For security reasons, which are probably detailed in your system's documentation for the C library tmpnam() function, this interface should not be used; instead see File::Temp.
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using the lc() function,
see lc, or the equivalent \L
operator inside doublequotish
strings.
This is identical to the C function, except that it can apply to a single
character or to a whole string. Consider using the uc() function,
see uc, or the equivalent \U
operator inside doublequotish
strings.
This is identical to the C function ttyname()
for returning the
name of the current terminal.
Retrieves the time conversion information from the tzname
variable.
- POSIX::tzset();
- ($std, $dst) = POSIX::tzname();
This is identical to the C function tzset()
for setting
the current timezone based on the environment variable TZ
,
to be used by ctime()
, localtime(), mktime()
, and strftime()
functions.
This is identical to Perl's builtin umask() function
for setting (and querying) the file creation permission mask,
see umask.
Get name of current operating system.
- ($sysname, $nodename, $release, $version, $machine) = POSIX::uname();
Note that the actual meanings of the various fields are not
that well standardized, do not expect any great portability.
The $sysname
might be the name of the operating system,
the $nodename
might be the name of the host, the $release
might be the (major) release number of the operating system,
the $version
might be the (minor) release number of the
operating system, and the $machine
might be a hardware identifier.
Maybe.
Use method IO::Handle::ungetc()
instead.
This is identical to Perl's builtin unlink() function
for removing files, see unlink.
This is identical to Perl's builtin utime() function
for changing the time stamps of files and directories,
see utime.
vfprintf() is C-specific, see printf instead.
vprintf() is C-specific, see printf instead.
vsprintf() is C-specific, see sprintf instead.
This is identical to Perl's builtin wait() function,
see wait.
Wait for a child process to change state. This is identical to Perl's
builtin waitpid() function, see waitpid.
- $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
- print "status = ", ($? / 256), "\n";
This is identical to the C function wcstombs()
.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
This is identical to the C function wctomb()
.
Perl does not have any support for the wide and multibyte
characters of the C standards, so this might be a rather
useless function.
Write to a file. This uses file descriptors such as those obtained by
calling POSIX::open
.
- $fd = POSIX::open( "foo", &POSIX::O_WRONLY );
- $buf = "hello";
- $bytes = POSIX::write( $fd, $buf, 5 );
Returns undef on failure.
See also syswrite.
Creates a new POSIX::SigAction
object which corresponds to the C
struct sigaction
. 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 POSIX::SigSet
object, it
defaults to the empty set. The third parameter contains the
sa_flags
, it defaults to 0.
- $sigset = POSIX::SigSet->new(SIGINT, SIGQUIT);
- $sigaction = POSIX::SigAction->new( \&handler, $sigset, &POSIX::SA_NOCLDSTOP );
This POSIX::SigAction
object is intended for use with the POSIX::sigaction()
function.
accessor functions to get/set the values of a SigAction object.
- $sigset = $sigaction->mask;
- $sigaction->flags(&POSIX::SA_RESTART);
accessor function for the "safe signals" flag of a SigAction object; see
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 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 POSIX::sigaction()
:
- sigaction(SIGINT, $new_action, $old_action);
- if ($old_action->safe) {
- # previous SIGINT handler used safe signals
- }
A hash of the POSIX realtime signal handlers. It is an extension of the standard %SIG, the $POSIX::SIGRT{SIGRTMIN} is roughly equivalent to $SIG{SIGRTMIN}, but the right POSIX moves (see below) are made with the POSIX::SigSet and POSIX::sigaction instead of accessing the %SIG.
You can set the %POSIX::SIGRT elements to set the POSIX realtime
signal handlers, use delete and exists on the elements, and use
scalar on the %POSIX::SIGRT
to find out how many POSIX realtime
signals there are available (SIGRTMAX - SIGRTMIN + 1, the SIGRTMAX is
a valid POSIX realtime signal).
Setting the %SIGRT elements is equivalent to calling this:
The flags default to zero, if you want something different you can
either use local on $POSIX::SigRt::SIGACTION_FLAGS, or you can
derive from POSIX::SigRt and define your own new()
(the tied hash
STORE method of the %SIGRT calls new($rtsig, $handler, $SIGACTION_FLAGS)
,
where the $rtsig ranges from zero to SIGRTMAX - SIGRTMIN + 1).
Just as with any signal, you can use sigaction($rtsig, undef, $oa) to retrieve the installed signal handler (or, rather, the signal action).
NOTE: whether POSIX realtime signals really work in your system, or whether Perl has been compiled so that it works with them, is outside of this discussion.
Return the minimum POSIX realtime signal number available, or undef
if no POSIX realtime signals are available.
Return the maximum POSIX realtime signal number available, or undef
if no POSIX realtime signals are available.
Create a new SigSet object. This object will be destroyed automatically when it is no longer needed. Arguments may be supplied to initialize the set.
Create an empty set.
- $sigset = POSIX::SigSet->new;
Create a set with SIGUSR1.
- $sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );
Add a signal to a SigSet object.
- $sigset->addset( &POSIX::SIGUSR2 );
Returns undef on failure.
Remove a signal from the SigSet object.
- $sigset->delset( &POSIX::SIGUSR2 );
Returns undef on failure.
Initialize the SigSet object to be empty.
- $sigset->emptyset();
Returns undef on failure.
Initialize the SigSet object to include all signals.
- $sigset->fillset();
Returns undef on failure.
Tests the SigSet object to see if it contains a specific signal.
- if( $sigset->ismember( &POSIX::SIGUSR1 ) ){
- print "contains SIGUSR1\n";
- }
Create a new Termios object. This object will be destroyed automatically when it is no longer needed. A Termios object corresponds to the termios C struct. new() mallocs a new one, getattr() fills it from a file descriptor, and setattr() sets a file descriptor's parameters to match Termios' contents.
- $termios = POSIX::Termios->new;
Get terminal control attributes.
Obtain the attributes for stdin.
- $termios->getattr( 0 ) # Recommended for clarity.
- $termios->getattr()
Obtain the attributes for stdout.
- $termios->getattr( 1 )
Returns undef on failure.
Retrieve a value from the c_cc field of a termios object. The c_cc field is an array so an index must be specified.
- $c_cc[1] = $termios->getcc(1);
Retrieve the c_cflag field of a termios object.
- $c_cflag = $termios->getcflag;
Retrieve the c_iflag field of a termios object.
- $c_iflag = $termios->getiflag;
Retrieve the input baud rate.
- $ispeed = $termios->getispeed;
Retrieve the c_lflag field of a termios object.
- $c_lflag = $termios->getlflag;
Retrieve the c_oflag field of a termios object.
- $c_oflag = $termios->getoflag;
Retrieve the output baud rate.
- $ospeed = $termios->getospeed;
Set terminal control attributes.
Set attributes immediately for stdout.
- $termios->setattr( 1, &POSIX::TCSANOW );
Returns undef on failure.
Set a value in the c_cc field of a termios object. The c_cc field is an array so an index must be specified.
- $termios->setcc( &POSIX::VEOF, 1 );
Set the c_cflag field of a termios object.
- $termios->setcflag( $c_cflag | &POSIX::CLOCAL );
Set the c_iflag field of a termios object.
- $termios->setiflag( $c_iflag | &POSIX::BRKINT );
Set the input baud rate.
- $termios->setispeed( &POSIX::B9600 );
Returns undef on failure.
Set the c_lflag field of a termios object.
- $termios->setlflag( $c_lflag | &POSIX::ECHO );
Set the c_oflag field of a termios object.
- $termios->setoflag( $c_oflag | &POSIX::OPOST );
Set the output baud rate.
- $termios->setospeed( &POSIX::B9600 );
Returns undef on failure.
B38400 B75 B200 B134 B300 B1800 B150 B0 B19200 B1200 B9600 B600 B4800 B50 B2400 B110
TCSADRAIN TCSANOW TCOON TCIOFLUSH TCOFLUSH TCION TCIFLUSH TCSAFLUSH TCIOFF TCOOFF
VEOF VEOL VERASE VINTR VKILL VQUIT VSUSP VSTART VSTOP VMIN VTIME NCCS
CLOCAL CREAD CSIZE CS5 CS6 CS7 CS8 CSTOPB HUPCL PARENB PARODD
BRKINT ICRNL IGNBRK IGNCR IGNPAR INLCR INPCK ISTRIP IXOFF IXON PARMRK
ECHO ECHOE ECHOK ECHONL ICANON IEXTEN ISIG NOFLSH TOSTOP
OPOST
_PC_CHOWN_RESTRICTED _PC_LINK_MAX _PC_MAX_CANON _PC_MAX_INPUT _PC_NAME_MAX _PC_NO_TRUNC _PC_PATH_MAX _PC_PIPE_BUF _PC_VDISABLE
_POSIX_ARG_MAX _POSIX_CHILD_MAX _POSIX_CHOWN_RESTRICTED _POSIX_JOB_CONTROL _POSIX_LINK_MAX _POSIX_MAX_CANON _POSIX_MAX_INPUT _POSIX_NAME_MAX _POSIX_NGROUPS_MAX _POSIX_NO_TRUNC _POSIX_OPEN_MAX _POSIX_PATH_MAX _POSIX_PIPE_BUF _POSIX_SAVED_IDS _POSIX_SSIZE_MAX _POSIX_STREAM_MAX _POSIX_TZNAME_MAX _POSIX_VDISABLE _POSIX_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
E2BIG EACCES EADDRINUSE EADDRNOTAVAIL EAFNOSUPPORT EAGAIN EALREADY EBADF EBUSY ECHILD ECONNABORTED ECONNREFUSED ECONNRESET EDEADLK EDESTADDRREQ EDOM EDQUOT EEXIST EFAULT EFBIG EHOSTDOWN EHOSTUNREACH EINPROGRESS EINTR EINVAL EIO EISCONN EISDIR ELOOP EMFILE EMLINK EMSGSIZE ENAMETOOLONG ENETDOWN ENETRESET ENETUNREACH ENFILE ENOBUFS ENODEV ENOENT ENOEXEC ENOLCK ENOMEM ENOPROTOOPT ENOSPC ENOSYS ENOTBLK ENOTCONN ENOTDIR ENOTEMPTY ENOTSOCK ENOTTY ENXIO EOPNOTSUPP EPERM EPFNOSUPPORT EPIPE EPROCLIM EPROTONOSUPPORT EPROTOTYPE ERANGE EREMOTE ERESTART EROFS ESHUTDOWN ESOCKTNOSUPPORT ESPIPE ESRCH ESTALE ETIMEDOUT ETOOMANYREFS ETXTBSY EUSERS EWOULDBLOCK EXDEV
FD_CLOEXEC F_DUPFD F_GETFD F_GETFL F_GETLK F_OK F_RDLCK F_SETFD F_SETFL F_SETLK F_SETLKW F_UNLCK F_WRLCK O_ACCMODE O_APPEND O_CREAT O_EXCL O_NOCTTY O_NONBLOCK O_RDONLY O_RDWR O_TRUNC O_WRONLY
DBL_DIG DBL_EPSILON DBL_MANT_DIG DBL_MAX DBL_MAX_10_EXP DBL_MAX_EXP DBL_MIN DBL_MIN_10_EXP DBL_MIN_EXP FLT_DIG FLT_EPSILON FLT_MANT_DIG FLT_MAX FLT_MAX_10_EXP FLT_MAX_EXP FLT_MIN FLT_MIN_10_EXP FLT_MIN_EXP FLT_RADIX FLT_ROUNDS LDBL_DIG LDBL_EPSILON LDBL_MANT_DIG LDBL_MAX LDBL_MAX_10_EXP LDBL_MAX_EXP LDBL_MIN LDBL_MIN_10_EXP LDBL_MIN_EXP
ARG_MAX CHAR_BIT CHAR_MAX CHAR_MIN CHILD_MAX INT_MAX INT_MIN LINK_MAX LONG_MAX LONG_MIN MAX_CANON MAX_INPUT MB_LEN_MAX NAME_MAX NGROUPS_MAX OPEN_MAX PATH_MAX PIPE_BUF SCHAR_MAX SCHAR_MIN SHRT_MAX SHRT_MIN SSIZE_MAX STREAM_MAX TZNAME_MAX UCHAR_MAX UINT_MAX ULONG_MAX USHRT_MAX
SA_NOCLDSTOP SA_NOCLDWAIT SA_NODEFER SA_ONSTACK SA_RESETHAND SA_RESTART SA_SIGINFO SIGABRT SIGALRM SIGCHLD SIGCONT SIGFPE SIGHUP SIGILL SIGINT SIGKILL SIGPIPE SIGQUIT SIGSEGV SIGSTOP SIGTERM SIGTSTP SIGTTIN SIGTTOU SIGUSR1 SIGUSR2 SIG_BLOCK SIG_DFL SIG_ERR SIG_IGN SIG_SETMASK SIG_UNBLOCK
S_IRGRP S_IROTH S_IRUSR S_IRWXG S_IRWXO S_IRWXU S_ISGID S_ISUID S_IWGRP S_IWOTH S_IWUSR S_IXGRP S_IXOTH S_IXUSR
S_ISBLK S_ISCHR S_ISDIR S_ISFIFO S_ISREG
WNOHANG WUNTRACED
WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIFSTOPPED WSTOPSIG
WIFEXITED($?) returns true if the child process exited normally
(exit() or by falling off the end of main()
)
WEXITSTATUS($?) returns the normal exit status of the child process (only meaningful if WIFEXITED($?) is true)
WIFSIGNALED($?) returns true if the child process terminated because of a signal
WTERMSIG($?) returns the signal the child process terminated for (only meaningful if WIFSIGNALED($?) is true)
WIFSTOPPED($?) returns true if the child process is currently stopped (can happen only if you specified the WUNTRACED flag to waitpid())
WSTOPSIG($?) returns the signal the child process was stopped for (only meaningful if WIFSTOPPED($?) is true)