POSIX

(source, CPAN)

version 1.38_03

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NAME
SYNOPSIS
DESCRIPTION
CAVEATS
FUNCTIONS
CLASSES
- POSIX::SigAction
- POSIX::SigRt
- POSIX::SigSet
- POSIX::Termios
PATHNAME CONSTANTS
POSIX CONSTANTS
SYSTEM CONFIGURATION
ERRNO
FCNTL
FLOAT
LIMITS
LOCALE
MATH
SIGNAL
STAT
STDLIB
STDIO
TIME
UNISTD
WAIT

#NAME

POSIX - Perl interface to IEEE Std 1003.1

#SYNOPSIS

    use POSIX ();
    use POSIX qw(setsid);
    use POSIX qw(:errno_h :fcntl_h);

    printf "EINTR is %d\n", EINTR;

    $sess_id = POSIX::setsid();

    $fd = POSIX::open($path, O_CREAT|O_EXCL|O_WRONLY, 0644);
	# note: that's a filedescriptor, *NOT* a filehandle

#DESCRIPTION

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 (e.g., POSIX::SEEK_END), or by giving an explicit import list. If you do neither, and opt for the default, use POSIX; has to import 553 symbols.

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.

#CAVEATS

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.

#FUNCTIONS

#_exit

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.

#abort

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).

#abs

This is identical to Perl's builtin abs() function, returning the absolute value of its numerical argument.

#access

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.

#acos

This is identical to the C function acos(), returning the arcus cosine of its numerical argument. See also Math::Trig.

#alarm

This is identical to Perl's builtin alarm() function, either for arming or disarming the SIGARLM timer.

#asctime

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.

#asin

This is identical to the C function asin(), returning the arcus sine of its numerical argument. See also Math::Trig.

#assert

Unimplemented, but you can use "die" in perlfunc and the Carp module to achieve similar things.

#atan

This is identical to the C function atan(), returning the arcus tangent of its numerical argument. See also Math::Trig.

#atan2

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

atexit() is C-specific: use END {} instead, see perlmod.

#atof

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

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" in perlfunc.

#atol

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" in perlfunc.

#bsearch

bsearch() not supplied. For doing binary search on wordlists, see Search::Dict.

#calloc

calloc() is C-specific. Perl does memory management transparently.

#ceil

This is identical to the C function ceil(), returning the smallest integer value greater than or equal to the given numerical argument.

#chdir

This is identical to Perl's builtin chdir() function, allowing one to change the working (default) directory, see "chdir" in perlfunc.

#chmod

This is identical to Perl's builtin chmod() function, allowing one to change file and directory permissions, see "chmod" in perlfunc.

#chown

This is identical to Perl's builtin chown() function, allowing one to change file and directory owners and groups, see "chown" in perlfunc.

#clearerr

Use the method IO::Handle::clearerr() instead, to reset the error state (if any) and EOF state (if any) of the given stream.

#clock

This is identical to the C function clock(), returning the amount of spent processor time in microseconds.

#close

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" in perlfunc.

#closedir

This is identical to Perl's builtin closedir() function for closing a directory handle, see "closedir" in perlfunc.

#cos

This is identical to Perl's builtin cos() function, for returning the cosine of its numerical argument, see "cos" in perlfunc. See also Math::Trig.

#cosh

This is identical to the C function cosh(), for returning the hyperbolic cosine of its numeric argument. See also Math::Trig.

#creat

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" in perlfunc and its O_CREAT flag.

#ctermid

Generates the path name for the controlling terminal.

$path = POSIX::ctermid();

#ctime

This is identical to the C function ctime() and equivalent to asctime(localtime(...)), see "asctime" and "localtime".

#cuserid

Get the login name of the owner of the current process.

$name = POSIX::cuserid();

#difftime

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

div() is C-specific, use "int" in perlfunc on the usual / division and the modulus %.

#dup

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.

#dup2

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.

#errno

Returns the value of errno.

$errno = POSIX::errno();

This identical to the numerical values of the $!, see "$ERRNO" in perlvar.

#execl

execl() is C-specific, see "exec" in perlfunc.

#execle

execle() is C-specific, see "exec" in perlfunc.

#execlp

execlp() is C-specific, see "exec" in perlfunc.

#execv

execv() is C-specific, see "exec" in perlfunc.

#execve

execve() is C-specific, see "exec" in perlfunc.

#execvp

execvp() is C-specific, see "exec" in perlfunc.

#exit

This is identical to Perl's builtin exit() function for exiting the program, see "exit" in perlfunc.

#exp

This is identical to Perl's builtin exp() function for returning the exponent (e-based) of the numerical argument, see "exp" in perlfunc.

#fabs

This is identical to Perl's builtin abs() function for returning the absolute value of the numerical argument, see "abs" in perlfunc.

#fclose

Use method IO::Handle::close() instead, or see "close" in perlfunc.

#fcntl

This is identical to Perl's builtin fcntl() function, see "fcntl" in perlfunc.

#fdopen

Use method IO::Handle::new_from_fd() instead, or see "open" in perlfunc.

#feof

Use method IO::Handle::eof() instead, or see "eof" in perlfunc.

#ferror

Use method IO::Handle::error() instead.

#fflush

Use method IO::Handle::flush() instead. See also "$OUTPUT_AUTOFLUSH" in perlvar.

#fgetc

Use method IO::Handle::getc() instead, or see "read" in perlfunc.

#fgetpos

Use method IO::Seekable::getpos() instead, or see "seek" in perlfunc.

#fgets

Use method IO::Handle::gets() instead. Similar to <>, also known as "readline" in perlfunc.

#fileno

Use method IO::Handle::fileno() instead, or see "fileno" in perlfunc.

#floor

This is identical to the C function floor(), returning the largest integer value less than or equal to the numerical argument.

#fmod

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.

#fopen

Use method IO::File::open() instead, or see "open" in perlfunc.

#fork

This is identical to Perl's builtin fork() function for duplicating the current process, see "fork" in perlfunc and perlfork if you are in Windows.

#fpathconf

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

fprintf() is C-specific, see "printf" in perlfunc instead.

#fputc

fputc() is C-specific, see "print" in perlfunc instead.

#fputs

fputs() is C-specific, see "print" in perlfunc instead.

#fread

fread() is C-specific, see "read" in perlfunc instead.

#free

free() is C-specific. Perl does memory management transparently.

#freopen

freopen() is C-specific, see "open" in perlfunc instead.

#frexp

Return the mantissa and exponent of a floating-point number.

($mantissa, $exponent) = POSIX::frexp( 1.234e56 );

#fscanf

fscanf() is C-specific, use <> and regular expressions instead.

#fseek

Use method IO::Seekable::seek() instead, or see "seek" in perlfunc.

#fsetpos

Use method IO::Seekable::setpos() instead, or seek "seek" in perlfunc.

#fstat

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 );

#fsync

Use method IO::Handle::sync() instead.

#ftell

Use method IO::Seekable::tell() instead, or see "tell" in perlfunc.

#fwrite

fwrite() is C-specific, see "print" in perlfunc instead.

#getc

This is identical to Perl's builtin getc() function, see "getc" in perlfunc.

#getchar

Returns one character from STDIN. Identical to Perl's getc(), see "getc" in perlfunc.

#getcwd

Returns the name of the current working directory. See also Cwd.

#getegid

Returns the effective group identifier. Similar to Perl' s builtin variable $(, see "$EGID" in perlvar.

#getenv

Returns the value of the specified environment variable. The same information is available through the %ENV array.

#geteuid

Returns the effective user identifier. Identical to Perl's builtin $> variable, see "$EUID" in perlvar.

#getgid

Returns the user's real group identifier. Similar to Perl's builtin variable $), see "$GID" in perlvar.

#getgrgid

This is identical to Perl's builtin getgrgid() function for returning group entries by group identifiers, see "getgrgid" in perlfunc.

#getgrnam

This is identical to Perl's builtin getgrnam() function for returning group entries by group names, see "getgrnam" in perlfunc.

#getgroups

Returns the ids of the user's supplementary groups. Similar to Perl's builtin variable $), see "$GID" in perlvar.

#getlogin

This is identical to Perl's builtin getlogin() function for returning the user name associated with the current session, see "getlogin" in perlfunc.

#getpgrp

This is identical to Perl's builtin getpgrp() function for returning the process group identifier of the current process, see "getpgrp" in perlfunc.

#getpid

Returns the process identifier. Identical to Perl's builtin variable $$, see "$PID" in perlvar.

#getppid

This is identical to Perl's builtin getppid() function for returning the process identifier of the parent process of the current process , see "getppid" in perlfunc.

#getpwnam

This is identical to Perl's builtin getpwnam() function for returning user entries by user names, see "getpwnam" in perlfunc.

#getpwuid

This is identical to Perl's builtin getpwuid() function for returning user entries by user identifiers, see "getpwuid" in perlfunc.

#gets

Returns one line from STDIN, similar to <>, also known as the readline() function, see "readline" in perlfunc.

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.

#getuid

Returns the user's identifier. Identical to Perl's builtin $< variable, see "$UID" in perlvar.

#gmtime

This is identical to Perl's builtin gmtime() function for converting seconds since the epoch to a date in Greenwich Mean Time, see "gmtime" in perlfunc.

#isalnum

Deprecated function whose use raises a warning, and which is slated to be removed in a future Perl version. It is very similar to matching against qr/ ^ [[:alnum:]]+ $ /x, which you should convert to use instead. The function is deprecated because 1) it doesn't handle UTF-8 encoded strings properly; and 2) it returns TRUE even if the input is the empty string. The function return is always based on the current locale, whereas using locale rules is optional with the regular expression, based on pragmas in effect and pattern modifiers (see "Character set modifiers" in perlre and "Which character set modifier is in effect?" in perlre).