POSIX.3pm - Online Linux Manual Page

POSIX - Online Linux Manual PageSection : 3pm
Updated : 2023-01-19
Source : perl v5.36.0
Note : Perl Programmers Reference Guide

NAMEPOSIX − 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

DESCRIPTIONThe 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. 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 or almost 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 notation [C99] indicates functions that were added in the ISO/IEC 9899:1999 version of the C language standard. Some may not be available on your system if it adheres to an earlier standard. Attempts to use any missing one will result in a fatal runtime error message.

CAVEATSEverything is exported by default (with a handful of exceptions). This is an unfortunate backwards compatibility feature and its use is strongly discouraged. You should either prevent the exporting (by saying use POSIX ();, as usual) and then use fully qualified names (e.g. POSIX::SEEK_END), or give an explicit import list. If you do neither and opt for the default (as in use POSIX;), you will import hundreds and hundreds of symbols into your namespace. 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 (except that POSIX::abs() must be provided an explicit value (rather than relying on an implicit $_): $absolute_value = POSIX::abs(42); # good $absolute_value = POSIX::abs(); # throws exception 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. acosh This is identical to the C function acosh(), returning the hyperbolic arcus cosine of its numerical argument [C99]. See also Math::Trig. Added in Perl v5.22. alarm This is identical to Perl's builtin alarm() function, either for arming or disarming the SIGARLM timer, except that POSIX::alarm() must be provided an explicit value (rather than relying on an implicit $_): POSIX::alarm(3) # good POSIX::alarm() # throws exception 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. Note the result is always in English. Use "strftime" instead to get a result suitable for the current locale. That function's %c format yields the locale's preferred representation. asin This is identical to the C function asin(), returning the arcus sine of its numerical argument. See also Math::Trig. asinh This is identical to the C function asinh(), returning the hyperbolic arcus sine of its numerical argument [C99]. See also Math::Trig. Added in Perl v5.22. 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. atanh This is identical to the C function atanh(), returning the hyperbolic arcus tangent of its numerical argument [C99]. See also Math::Trig. Added in Perl v5.22. 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 Not implemented. atexit() is C−specific: use END {} instead, see perlmod. atof Not implemented. 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 Not implemented. 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 Not implemented. 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 Not implemented. calloc() is C−specific. Perl does memory management transparently. cbrt The cube root [C99]. Added in Perl v5.22. 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 \*(L"chdir\*(R" in perlfunc \*(-- with the exception that POSIX::chdir() must be provided an explicit value (rather than relying on an implicit $_): $rv = POSIX::chdir('path/to/dir'); # good $rv = POSIX::chdir(); # throws exception chmod This is identical to Perl's builtin chmod() function, allowing one to change file and directory permissions \*(-- see \*(L"chmod\*(R" in perlfunc \*(-- with the exception that POSIX::chmod() can only change one file at a time (rather than a list of files): $c = chmod 0664, $file1, $file2; # good $c = POSIX::chmod 0664, $file1; # throws exception $c = POSIX::chmod 0664, $file1, $file2; # throws exception As with the built-in chmod(), $file may be a filename or a file handle. 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 Not implemented. 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. copysign Returns x but with the sign of y [C99]. Added in Perl v5.22. $x_with_sign_of_y = POSIX::copysign($x, $y); See also ‟signbit”. 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 [POSIX.1−1988] Get the login name of the owner of the current process. $name = POSIX::cuserid(); Note: this function has not been specified by POSIX since 1990 and is included only for backwards compatibility. New code should use getlogin() instead. 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 Not implemented. 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. erf The error function [C99]. Added in Perl v5.22. erfc The complementary error function [C99]. Added in Perl v5.22. errno Returns the value of errno. $errno = POSIX::errno(); This identical to the numerical values of the $!, see ‟$ERRNO” in perlvar. execl Not implemented. execl() is C−specific, see ‟exec” in perlfunc. execle Not implemented. execle() is C−specific, see ‟exec” in perlfunc. execlp Not implemented. execlp() is C−specific, see ‟exec” in perlfunc. execv Not implemented. execv() is C−specific, see ‟exec” in perlfunc. execve Not implemented. execve() is C−specific, see ‟exec” in perlfunc. execvp Not implemented. 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. expm1 Equivalent to exp(x) − 1, but more precise for small argument values [C99]. Added in Perl v5.22. See also ‟log1p”. fabs This is identical to Perl's builtin abs() function for returning the absolute value of the numerical argument, see ‟abs” in perlfunc. fclose Not implemented. 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 Not implemented. Use method IO::Handle::new_from_fd() instead, or see ‟open” in perlfunc. feof Not implemented. Use method IO::Handle::eof() instead, or see ‟eof” in perlfunc. ferror Not implemented. Use method IO::Handle::error() instead. fflush Not implemented. Use method IO::Handle::flush() instead. See also "$OUTPUT_AUTOFLUSH" in perlvar. fgetc Not implemented. Use method IO::Handle::getc() instead, or see ‟read” in perlfunc. fgetpos Not implemented. Use method IO::Seekable::getpos() instead, or see ‟seek” in perlfunc. fgets Not implemented. Use method IO::Handle::gets() instead. Similar to <>, also known as ‟readline” in perlfunc. fileno Not implemented. 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. fdim ‟Positive difference”, x − y if x > y, zero otherwise [C99]. Added in Perl v5.22. fegetround Returns the current floating point rounding mode, one of FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_DOWNWARD FE_TONEAREST is like ‟round”, FE_TOWARDZERO is like ‟trunc” [C99]. Added in Perl v5.22. fesetround Sets the floating point rounding mode, see ‟fegetround” [C99]. Added in Perl v5.22. fma ‟Fused multiply-add”, x * y + z, possibly faster (and less lossy) than the explicit two operations [C99]. Added in Perl v5.22. my $fused = POSIX::fma($x, $y, $z); fmax Maximum of x and y, except when either is NaN, returns the other [C99]. Added in Perl v5.22. my $min = POSIX::fmax($x, $y); fmin Minimum of x and y, except when either is NaN, returns the other [C99]. Added in Perl v5.22. my $min = POSIX::fmin($x, $y); 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 Not implemented. 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. fpclassify Returns one of FP_NORMAL FP_ZERO FP_SUBNORMAL FP_INFINITE FP_NAN telling the class of the argument [C99]. FP_INFINITE is positive or negative infinity, FP_NAN is not-a-number. FP_SUBNORMAL means subnormal numbers (also known as denormals), very small numbers with low precision. FP_ZERO is zero. FP_NORMAL is all the rest. Added in Perl v5.22. fprintf Not implemented. fprintf() is C−specific, see ‟printf” in perlfunc instead. fputc Not implemented. fputc() is C−specific, see ‟print” in perlfunc instead. fputs Not implemented. fputs() is C−specific, see ‟print” in perlfunc instead. fread Not implemented. fread() is C−specific, see ‟read” in perlfunc instead. free Not implemented. free() is C−specific. Perl does memory management transparently. freopen Not implemented. 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 Not implemented. fscanf() is C−specific, use <> and regular expressions instead. fseek Not implemented. Use method IO::Seekable::seek() instead, or see ‟seek” in perlfunc. fsetpos Not implemented. 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 Not implemented. Use method IO::Handle::sync() instead. ftell Not implemented. Use method IO::Seekable::tell() instead, or see ‟tell” in perlfunc. fwrite Not implemented. 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. getpayload use POSIX ':nan_payload'; getpayload($var) Returns the NaN payload. Added in Perl v5.24. Note the API instability warning in ‟setpayload”. See ‟nan” for more discussion about NaN. 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. hypot Equivalent to sqrt(x * x + y * y) except more stable on very large or very small arguments [C99]. Added in Perl v5.22. ilogb Integer binary logarithm [C99]. Added in Perl v5.22. For example ilogb(20) is 4, as an integer. See also ‟logb”. Inf The infinity as a constant: use POSIX qw(Inf); my $pos_inf = +Inf; # Or just Inf. my $neg_inf = −Inf; See also ‟isinf”, and ‟fpclassify”. isalnum This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:alnum:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isalpha This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:alpha:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isatty Returns a boolean indicating whether the specified filehandle is connected to a tty. Similar to the −t operator, see ‟−X” in perlfunc. iscntrl This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:cntrl:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isdigit This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:digit:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isfinite Returns true if the argument is a finite number (that is, not an infinity, or the not-a-number) [C99]. Added in Perl v5.22. See also ‟isinf”, ‟isnan”, and ‟fpclassify”. isgraph This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:graph:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isgreater (Also isgreaterequal, isless, islessequal, islessgreater, isunordered) Floating point comparisons which handle the NaN [C99]. Added in Perl v5.22. isinf Returns true if the argument is an infinity (positive or negative) [C99]. Added in Perl v5.22. See also ‟Inf”, ‟isnan”, ‟isfinite”, and ‟fpclassify”. islower This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:lower:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isnan Returns true if the argument is NaN (not-a-number) [C99]. Added in Perl v5.22. Note that you can also test for "NaN−ness" with equality operators (== or !=), as in print "x is not a NaN\n" if $x == $x; since the NaN is not equal to anything, including itself. See also ‟nan”, ‟NaN”, ‟isinf”, and ‟fpclassify”. isnormal Returns true if the argument is normal (that is, not a subnormal/denormal, and not an infinity, or a not-a-number) [C99]. Added in Perl v5.22. See also ‟isfinite”, and ‟fpclassify”. isprint This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:print:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. ispunct This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:punct:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. issignaling use POSIX ':nan_payload'; issignaling($var, $payload) Return true if the argument is a signaling NaN. Added in Perl v5.24. Note the API instability warning in ‟setpayload”. See ‟nan” for more discussion about NaN. isspace This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:space:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isupper This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:upper:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. isxdigit This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:xdigit:]]+ $ /x, which you should convert to use instead. See ‟POSIX Character Classes” in perlrecharclass. j0 j1 jn y0 y1 yn The Bessel function of the first kind of the order zero. kill This is identical to Perl's builtin kill() function for sending signals to processes (often to terminate them), see ‟kill” in perlfunc. labs Not implemented. (For returning absolute values of long integers.) labs() is C−specific, see ‟abs” in perlfunc instead. lchown This is identical to the C function, except the order of arguments is consistent with Perl's builtin chown() with the added restriction of only one path, not a list of paths. Does the same thing as the chown() function but changes the owner of a symbolic link instead of the file the symbolic link points to. POSIX::lchown($uid, $gid, $file_path); ldexp This is identical to the C function ldexp() for multiplying floating point numbers with powers of two. $x_quadrupled = POSIX::ldexp($x, 2); ldiv Not implemented. (For computing dividends of long integers.) ldiv() is C−specific, use / and int() instead. lgamma The logarithm of the Gamma function [C99]. Added in Perl v5.22. See also ‟tgamma”. log1p Equivalent to log(1 + x), but more stable results for small argument values [C99]. Added in Perl v5.22. log2 Logarithm base two [C99]. Added in Perl v5.22. See also ‟expm1”. logb Integer binary logarithm [C99]. Added in Perl v5.22. For example logb(20) is 4, as a floating point number. See also ‟ilogb”. link This is identical to Perl's builtin link() function for creating hard links into files, see ‟link” in perlfunc. localeconv Get numeric formatting information. Returns a reference to a hash containing the formatting values of the locale that currently underlies the program, regardless of whether or not it is called from within the scope of a use locale. Users of this function should also read perllocale, which provides a comprehensive discussion of Perl locale handling, including a section devoted to this function. Prior to Perl 5.28, or when operating in a non thread-safe environment, it should not be used in a threaded application unless it's certain that the underlying locale is C or POSIX. This is because it otherwise changes the locale, which globally affects all threads simultaneously. Windows platforms starting with Visual Studio 2005 are mostly thread-safe, but use of this function in those prior to Visual Studio 2015 can have a race with a thread that has called ‟switch_to_global_locale” in perlapi. Here is how to query the database for the de (Deutsch or German) locale. my $loc = POSIX::setlocale( &POSIX::LC_ALL, "de" ); print "Locale: \"$loc\"\n"; my $lconv = POSIX::localeconv(); foreach my $property (qw( decimal_point thousands_sep grouping int_curr_symbol currency_symbol mon_decimal_point mon_thousands_sep mon_grouping positive_sign negative_sign int_frac_digits frac_digits p_cs_precedes p_sep_by_space n_cs_precedes n_sep_by_space p_sign_posn n_sign_posn int_p_cs_precedes int_p_sep_by_space int_n_cs_precedes int_n_sep_by_space int_p_sign_posn int_n_sign_posn )) { printf qq(%s: "%s",\n), $property, $lconv−>{$property}; } The members whose names begin with int_p_ and int_n_ were added by POSIX.1−2008 and are only available on systems that support them. localtime This is identical to Perl's builtin localtime() function for converting seconds since the epoch to a date see ‟localtime” in perlfunc except that POSIX::localtime() must be provided an explicit value (rather than relying on an implicit $_): @localtime = POSIX::localtime(time); # good @localtime = localtime(); # good @localtime = POSIX::localtime(); # throws exception log This is identical to Perl's builtin log() function, returning the natural (e−based) logarithm of the numerical argument, see ‟log” in perlfunc. log10 This is identical to the C function log10(), returning the 10−base logarithm of the numerical argument. You can also use sub log10 { log($_[0]) / log(10) } or sub log10 { log($_[0]) / 2.30258509299405 } or sub log10 { log($_[0]) * 0.434294481903252 } longjmp Not implemented. longjmp() is C−specific: use ‟die” in perlfunc instead. lseek 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. lrint Depending on the current floating point rounding mode, rounds the argument either toward nearest (like ‟round”), toward zero (like ‟trunc”), downward (toward negative infinity), or upward (toward positive infinity) [C99]. Added in Perl v5.22. For the rounding mode, see ‟fegetround”. lround Like ‟round”, but as integer, as opposed to floating point [C99]. Added in Perl v5.22. See also ‟ceil”, ‟floor”, ‟trunc”. Owing to an oversight, this is not currently exported by default, or as part of the :math_h_c99 export tag; importing it must therefore be done by explicit name. malloc Not implemented. malloc() is C−specific. Perl does memory management transparently. mblen This is the same as the C function mblen() on unthreaded perls. On threaded perls, it transparently (almost) substitutes the more thread-safe mbrlen(3), if available, instead of mblen. Core Perl does not have any support for wide and multibyte locales, except Unicode UTF−8 locales. This function, in conjunction with ‟mbtowc” and ‟wctomb” may be used to roll your own decoding/encoding of other types of multi-byte locales. Use undef as the first parameter to this function to get the effect of passing NULL as the first parameter to mblen. This resets any shift state to its initial value. The return value is undefined if mbrlen was substituted, so you should never rely on it. When the first parameter is a scalar containing a value that either is a PV string or can be forced into one, the return value is the number of bytes occupied by the first character of that string; or 0 if that first character is the wide NUL character; or negative if there is an error. This is based on the locale that currently underlies the program, regardless of whether or not the function is called from Perl code that is within the scope of use locale. Perl makes no attempt at hiding from your code any differences in the errno setting between mblen and mbrlen. It does set errno to 0 before calling them. The optional second parameter is ignored if it is larger than the actual length of the first parameter string. mbtowc This is the same as the C function mbtowc() on unthreaded perls. On threaded perls, it transparently (almost) substitutes the more thread-safe mbrtowc(3), if available, instead of mbtowc. Core Perl does not have any support for wide and multibyte locales, except Unicode UTF−8 locales. This function, in conjunction with ‟mblen” and ‟wctomb” may be used to roll your own decoding/encoding of other types of multi-byte locales. The first parameter is a scalar into which, upon success, the wide character represented by the multi-byte string contained in the second parameter is stored. The optional third parameter is ignored if it is larger than the actual length of the second parameter string. Use undef as the second parameter to this function to get the effect of passing NULL as the second parameter to mbtowc. This resets any shift state to its initial value. The return value is undefined if mbrtowc was substituted, so you should never rely on it. When the second parameter is a scalar containing a value that either is a PV string or can be forced into one, the return value is the number of bytes occupied by the first character of that string; or 0 if that first character is the wide NUL character; or negative if there is an error. This is based on the locale that currently underlies the program, regardless of whether or not the function is called from Perl code that is within the scope of use locale. Perl makes no attempt at hiding from your code any differences in the errno setting between mbtowc and mbrtowc. It does set errno to 0 before calling them. memchr Not implemented. memchr() is C−specific, see ‟index” in perlfunc instead. memcmp Not implemented. memcmp() is C−specific, use eq instead, see perlop. memcpy Not implemented. memcpy() is C−specific, use =, see perlop, or see ‟substr” in perlfunc. memmove Not implemented. memmove() is C−specific, use =, see perlop, or see ‟substr” in perlfunc. memset Not implemented. memset() is C−specific, use x instead, see perlop. mkdir This is identical to Perl's builtin mkdir() function for creating directories, see ‟mkdir” in perlfunc. mkfifo 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” in perlfunc, though for mkfifo you must specify the $mode. mktime 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. modf Return the integral and fractional parts of a floating-point number. ($fractional, $integral) = POSIX::modf( 3.14 ); See also ‟round”. NaN The not-a-number as a constant: use POSIX qw(NaN); my $nan = NaN; See also ‟nan”, /isnan, and ‟fpclassify”. nan my $nan = nan(); Returns NaN, not-a-number [C99]. Added in Perl v5.22. The returned NaN is always a quiet NaN, as opposed to signaling. With an argument, can be used to generate a NaN with payload. The argument is first interpreted as a floating point number, but then any fractional parts are truncated (towards zero), and the value is interpreted as an unsigned integer. The bits of this integer are stored in the unused bits of the NaN. The result has a dual nature: it is a NaN, but it also carries the integer inside it. The integer can be retrieved with ‟getpayload”. Note, though, that the payload is not propagated, not even on copies, and definitely not in arithmetic operations. How many bits fit in the NaN depends on what kind of floating points are being used, but on the most common platforms (64−bit IEEE 754, or the x86 80−bit long doubles) there are 51 and 61 bits available, respectively. (There would be 52 and 62, but the quiet/signaling bit of NaNs takes away one.) However, because of the floating−point−to− integer-and-back conversions, please test carefully whether you get back what you put in. If your integers are only 32 bits wide, you probably should not rely on more than 32 bits of payload. Whether a ‟signaling” NaN is in any way different from a ‟quiet” NaN, depends on the platform. Also note that the payload of the default NaN (no argument to nan()) is not necessarily zero, use setpayload to explicitly set the payload. On some platforms like the 32−bit x86, (unless using the 80−bit long doubles) the signaling bit is not supported at all. See also ‟isnan”, ‟NaN”, ‟setpayload” and ‟issignaling”. nearbyint Returns the nearest integer to the argument, according to the current rounding mode (see ‟fegetround”) [C99]. Added in Perl v5.22. nextafter Returns the next representable floating point number after x in the direction of y [C99]. Added in Perl v5.22. my $nextafter = POSIX::nextafter($x, $y); Like ‟nexttoward”, but potentially less accurate. nexttoward Returns the next representable floating point number after x in the direction of y [C99]. Added in Perl v5.22. my $nexttoward = POSIX::nexttoward($x, $y); Like ‟nextafter”, but potentially more accurate. nice This is similar to the C function nice(), for changing the scheduling preference of the current process. Positive arguments mean a more polite process, negative values a more needy process. Normal (non-root) user processes can only change towards being more polite. Returns undef on failure. offsetof Not implemented. offsetof() is C−specific, you probably want to see ‟pack” in perlfunc instead. open 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” in perlfunc. opendir Open a directory for reading. $dir = POSIX::opendir( "/var" ); @files = POSIX::readdir( $dir ); POSIX::closedir( $dir ); Returns undef on failure. pathconf 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. pause 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. perror 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” in perlfunc and ‟$ERRNO” in perlvar. pipe 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” in perlfunc. pow Computes $x raised to the power $exponent. $ret = POSIX::pow( $x, $exponent ); You can also use the ** operator, see perlop. printf Formats and prints the specified arguments to STDOUT. See also ‟printf” in perlfunc. putc Not implemented. putc() is C−specific, see ‟print” in perlfunc instead. putchar Not implemented. putchar() is C−specific, see ‟print” in perlfunc instead. puts Not implemented. puts() is C−specific, see ‟print” in perlfunc instead. qsort Not implemented. qsort() is C−specific, see ‟sort” in perlfunc instead. raise Sends the specified signal to the current process. See also ‟kill” in perlfunc and the $$ in ‟$PID” in perlvar. rand Not implemented. rand() is non-portable, see ‟rand” in perlfunc instead. read 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” in perlfunc. readdir This is identical to Perl's builtin readdir() function for reading directory entries, see ‟readdir” in perlfunc. realloc Not implemented. realloc() is C−specific. Perl does memory management transparently. remainder Given x and y, returns the value x − n*y, where n is the integer closest to x/y [C99]. Added in Perl v5.22. my $remainder = POSIX::remainder($x, $y) See also ‟remquo”. remove Deletes a name from the filesystem. Calls ‟unlink” in perlfunc for files and ‟rmdir” in perlfunc for directories. remquo Like ‟remainder” but also returns the low-order bits of the quotient (n) [C99]. Added in Perl v5.22. (This is quite esoteric interface, mainly used to implement numerical algorithms.) rename This is identical to Perl's builtin rename() function for renaming files, see ‟rename” in perlfunc. rewind Seeks to the beginning of the file. rewinddir This is identical to Perl's builtin rewinddir() function for rewinding directory entry streams, see ‟rewinddir” in perlfunc. rint Identical to ‟lrint”. rmdir This is identical to Perl's builtin rmdir() function for removing (empty) directories, see ‟rmdir” in perlfunc. round Returns the integer (but still as floating point) nearest to the argument [C99]. Added in Perl v5.22. See also ‟ceil”, ‟floor”, ‟lround”, ‟modf”, and ‟trunc”. scalbn Returns x * 2**y [C99]. Added in Perl v5.22. See also ‟frexp” and ‟ldexp”. scanf Not implemented. scanf() is C−specific, use <> and regular expressions instead, see perlre. setgid 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. setjmp Not implemented. setjmp() is C−specific: use eval {} instead, see ‟eval” in perlfunc. setlocale WARNING! Prior to Perl 5.28 or on a system that does not support thread-safe locale operations, do NOT use this function in a thread. The locale will change in all other threads at the same time, and should your thread get paused by the operating system, and another started, that thread will not have the locale it is expecting. On some platforms, there can be a race leading to segfaults if two threads call this function nearly simultaneously. This warning does not apply on unthreaded builds, or on perls where ${^SAFE_LOCALES} exists and is non-zero; namely Perl 5.28 and later compiled to be locale-thread-safe. This function modifies and queries the program's underlying locale. Users of this function should read perllocale, whch provides a comprehensive discussion of Perl locale handling, knowledge of which is necessary to properly use this function. It contains a section devoted to this function. The discussion here is merely a summary reference for setlocale(). Note that Perl itself is almost entirely unaffected by the locale except within the scope of "use locale". (Exceptions are listed in ‟Not within the scope of ”use locale"" in perllocale, and locale-dependent functions within the POSIX module ARE always affected by the current 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 system's 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. $loc = setlocale( LC_COLLATE, "es_AR.ISO8859−1" ); setpayload use POSIX ':nan_payload'; setpayload($var, $payload); Sets the NaN payload of var. Added in Perl v5.24. NOTE: the NaN payload APIs are based on the latest (as of June 2015) proposed ISO C interfaces, but they are not yet a standard. Things may change. See ‟nan” for more discussion about NaN. See also ‟setpayloadsig”, ‟isnan”, ‟getpayload”, and ‟issignaling”. setpayloadsig use POSIX ':nan_payload'; setpayloadsig($var, $payload); Like ‟setpayload” but also makes the NaN signaling. Added in Perl v5.24. Depending on the platform the NaN may or may not behave differently. Note the API instability warning in ‟setpayload”. Note that because how the floating point formats work out, on the most common platforms signaling payload of zero is best avoided, since it might end up being identical to +Inf. See also ‟nan”, ‟isnan”, ‟getpayload”, and ‟issignaling”. setpgid This is similar to the C function setpgid() for setting the process group identifier of the current process. Returns undef on failure. setsid This is identical to the C function setsid() for setting the session identifier of the current process. setuid 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. sigaction 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 constants for specific code values can be imported individually or using the :signal_h_si_code tag, since Perl v5.24. 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 addr address of faulting instruction or memory reference for SIGILL, SIGFPE, SIGSEGV or SIGBUS 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 Not implemented. siglongjmp() is C−specific: use ‟die” in perlfunc instead. signbit Returns zero for positive arguments, non-zero for negative arguments [C99]. Added in Perl v5.22. sigpending 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. sigprocmask 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. Note that you can't reliably block or unblock a signal from its own signal handler if you're using safe signals. Other signals can be blocked or unblocked reliably. sigsetjmp Not implemented. sigsetjmp() is C−specific: use eval {} instead, see ‟eval” in perlfunc. sigsuspend 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. sin This is identical to Perl's builtin sin() function for returning the sine of the numerical argument, see ‟sin” in perlfunc. See also Math::Trig. sinh This is identical to the C function sinh() for returning the hyperbolic sine of the numerical argument. See also Math::Trig. sleep 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” in perlfunc. There is one significant difference, however: POSIX::sleep() returns the number of unslept seconds, while the CORE::sleep() returns the number of slept seconds. sprintf This is similar to Perl's builtin sprintf() function for returning a string that has the arguments formatted as requested, see ‟sprintf” in perlfunc. sqrt This is identical to Perl's builtin sqrt() function. for returning the square root of the numerical argument, see ‟sqrt” in perlfunc. srand Give a seed the pseudorandom number generator, see ‟srand” in perlfunc. sscanf Not implemented. sscanf() is C−specific, use regular expressions instead, see perlre. stat This is identical to Perl's builtin stat() function for returning information about files and directories. strcat Not implemented. strcat() is C−specific, use .= instead, see perlop. strchr Not implemented. strchr() is C−specific, see ‟index” in perlfunc instead. strcmp Not implemented. strcmp() is C−specific, use eq or cmp instead, see perlop. strcoll 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. Beware that in a UTF−8 locale, anything you pass to this function must be in UTF−8; and when not in a UTF−8 locale, anything passed must not be UTF−8 encoded. Note also that it doesn't make sense for a string to be encoded in one locale (say, ISO−8859−6, Arabic) and to collate it based on another (like ISO−8859−7, Greek). The results will be essentially meaningless. strcpy Not implemented. strcpy() is C−specific, use = instead, see perlop. strcspn Not implemented. strcspn() is C−specific, use regular expressions instead, see perlre. strerror Returns the error string for the specified errno. Identical to the string form of $!, see ‟$ERRNO” in perlvar. strftime 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"; strlen Not implemented. strlen() is C−specific, use length() instead, see ‟length” in perlfunc. strncat Not implemented. strncat() is C−specific, use .= instead, see perlop. strncmp Not implemented. strncmp() is C−specific, use eq instead, see perlop. strncpy Not implemented. strncpy() is C−specific, use = instead, see perlop. strpbrk Not implemented. strpbrk() is C−specific, use regular expressions instead, see perlre. strrchr Not implemented. strrchr() is C−specific, see ‟rindex” in perlfunc instead. strspn Not implemented. strspn() is C−specific, use regular expressions instead, see perlre. strstr This is identical to Perl's builtin index() function, see ‟index” in perlfunc. strtod 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 respects any POSIX setlocale() LC_NUMERIC settings, regardless of whether or not it is called from Perl code that is within the scope of use locale. Prior to Perl 5.28, or when operating in a non thread-safe environment, it should not be used in a threaded application unless it's certain that the underlying locale is C or POSIX. This is because it otherwise changes the locale, which globally affects all threads simultaneously. 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 Not implemented. strtok() is C−specific, use regular expressions instead, see perlre, or ‟split” in perlfunc. strtol 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. strtold Like ‟strtod” but for long doubles. Defined only if the system supports long doubles. strtoul 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. strxfrm String transformation. Returns the transformed string. $dst = POSIX::strxfrm( $src ); Used with eq or cmp as an alternative to "strcoll". Not really needed since Perl can do this transparently, see perllocale. Beware that in a UTF−8 locale, anything you pass to this function must be in UTF−8; and when not in a UTF−8 locale, anything passed must not be UTF−8 encoded. sysconf Retrieves values of system configurable variables. The following will get the machine's clock speed. $clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK ); Returns undef on failure. system This is identical to Perl's builtin system() function, see ‟system” in perlfunc. tan This is identical to the C function tan(), returning the tangent of the numerical argument. See also Math::Trig. tanh This is identical to the C function tanh(), returning the hyperbolic tangent of the numerical argument. See also Math::Trig. tcdrain This is similar to the C function tcdrain() for draining the output queue of its argument stream. Returns undef on failure. tcflow This is similar to the C function tcflow() for controlling the flow of its argument stream. Returns undef on failure. tcflush This is similar to the C function tcflush() for flushing the I/O buffers of its argument stream. Returns undef on failure. tcgetpgrp This is identical to the C function tcgetpgrp() for returning the process group identifier of the foreground process group of the controlling terminal. tcsendbreak This is similar to the C function tcsendbreak() for sending a break on its argument stream. Returns undef on failure. tcsetpgrp This is similar to the C function tcsetpgrp() for setting the process group identifier of the foreground process group of the controlling terminal. Returns undef on failure. tgamma The Gamma function [C99]. Added in Perl v5.22. See also ‟lgamma”. time This is identical to Perl's builtin time() function for returning the number of seconds since the epoch (whatever it is for the system), see ‟time” in perlfunc. times The times() function returns elapsed realtime since some point in the past (such as system startup), user and system times for this process, and user and system times used by child processes. All times are returned in clock ticks. ($realtime, $user, $system, $cuser, $csystem) = POSIX::times(); Note: Perl's builtin times() function returns four values, measured in seconds. tmpfile Not implemented. Use method IO::File::new_tmpfile() instead, or see File::Temp. tmpnam For security reasons, which are probably detailed in your system's documentation for the C library tmpnam() function, this interface is no longer available since Perl v5.26; instead use File::Temp. tolower This function has been removed as of Perl v5.26. This is identical to the C function, except that it can apply to a single character or to a whole string, and currently operates as if the locale always is ‟C”. Consider using the lc() function, see ‟lc” in perlfunc, see ‟lc” in perlfunc, or the equivalent \L operator inside doublequotish strings. toupper This function has been removed as of Perl v5.26. This is similar to the C function, except that it can apply to a single character or to a whole string, and currently operates as if the locale always is ‟C”. Consider using the uc() function, see ‟uc” in perlfunc, or the equivalent \U operator inside doublequotish strings. trunc Returns the integer toward zero from the argument [C99]. Added in Perl v5.22. See also ‟ceil”, ‟floor”, and ‟round”. ttyname This is identical to the C function ttyname() for returning the name of the current terminal. tzname Retrieves the time conversion information from the tzname variable. POSIX::tzset(); ($std, $dst) = POSIX::tzname(); tzset This is identical to the C function tzset() for setting the current timezone based on the environment variable TZ, to be used by ctime(), localtime(), mktime(), and strftime() functions. umask This is identical to Perl's builtin umask() function for setting (and querying) the file creation permission mask, see ‟umask” in perlfunc. uname Get name of current operating system. ($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. ungetc Not implemented. Use method IO::Handle::ungetc() instead. unlink This is identical to Perl's builtin unlink() function for removing files, see ‟unlink” in perlfunc. utime This is identical to Perl's builtin utime() function for changing the time stamps of files and directories, see ‟utime” in perlfunc. vfprintf Not implemented. vfprintf() is C−specific, see ‟printf” in perlfunc instead. vprintf Not implemented. vprintf() is C−specific, see ‟printf” in perlfunc instead. vsprintf Not implemented. vsprintf() is C−specific, see ‟sprintf” in perlfunc instead. wait This is identical to Perl's builtin wait() function, see ‟wait” in perlfunc. waitpid Wait for a child process to change state. This is identical to Perl's builtin waitpid() function, see ‟waitpid” in perlfunc. $pid = POSIX::waitpid( −1, POSIX::WNOHANG ); print "status = ", ($? / 256), "\n"; See ‟mblen”. wctomb This is the same as the C function wctomb() on unthreaded perls. On threaded perls, it transparently (almost) substitutes the more thread-safe wcrtomb(3), if available, instead of wctomb. Core Perl does not have any support for wide and multibyte locales, except Unicode UTF−8 locales. This function, in conjunction with ‟mblen” and ‟mbtowc” may be used to roll your own decoding/encoding of other types of multi-byte locales. Use undef as the first parameter to this function to get the effect of passing NULL as the first parameter to wctomb. This resets any shift state to its initial value. The return value is undefined if wcrtomb was substituted, so you should never rely on it. When the first parameter is a scalar, the code point contained in the scalar second parameter is converted into a multi-byte string and stored into the first parameter scalar. This is based on the locale that currently underlies the program, regardless of whether or not the function is called from Perl code that is within the scope of use locale. The return value is the number of bytes stored; or negative if the code point isn't representable in the current locale. Perl makes no attempt at hiding from your code any differences in the errno setting between wctomb and wcrtomb. It does set errno to 0 before calling them. write 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” in perlfunc.

CLASSES

POSIX::SigActionnew 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. handler mask flags accessor functions to get/set the values of a SigAction object. $sigset = $sigaction−>mask; $sigaction−>flags(&POSIX::SA_RESTART); safe 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 }

POSIX::SigRt%SIGRT A hash of the POSIX realtime signal handlers. It is an extension of the standard %SIG, the $POSIX::SIGRT{SIGRTMIN} is roughly equivalent to $SIG{SIGRTMIN}, but the right POSIX moves (see below) are made with the POSIX::SigSet and POSIX::sigaction instead of accessing the %SIG. You can set the %POSIX::SIGRT elements to set the POSIX realtime signal handlers, use delete and exists on the elements, and use scalar on the %POSIX::SIGRT to find out how many POSIX realtime signals there are available (SIGRTMAX − SIGRTMIN + 1, the SIGRTMAX is a valid POSIX realtime signal). Setting the %SIGRT elements is equivalent to calling this: sub new { my ($rtsig, $handler, $flags) = @_; my $sigset = POSIX::SigSet($rtsig); my $sigact = POSIX::SigAction−>new($handler,$sigset,$flags); sigaction($rtsig, $sigact); } 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. SIGRTMIN Return the minimum POSIX realtime signal number available, or undef if no POSIX realtime signals are available. SIGRTMAX Return the maximum POSIX realtime signal number available, or undef if no POSIX realtime signals are available.

POSIX::SigSetnew 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 ); Throws an error if any of the signals supplied cannot be added to the set. addset Add a signal to a SigSet object. $sigset−>addset( &POSIX::SIGUSR2 ); Returns undef on failure. delset Remove a signal from the SigSet object. $sigset−>delset( &POSIX::SIGUSR2 ); Returns undef on failure. emptyset Initialize the SigSet object to be empty. $sigset−>emptyset(); Returns undef on failure. fillset Initialize the SigSet object to include all signals. $sigset−>fillset(); Returns undef on failure. ismember Tests the SigSet object to see if it contains a specific signal. if( $sigset−>ismember( &POSIX::SIGUSR1 ) ){ print "contains SIGUSR1\n"; }

POSIX::Termiosnew 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; getattr 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. getcc 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); getcflag Retrieve the c_cflag field of a termios object. $c_cflag = $termios−>getcflag; getiflag Retrieve the c_iflag field of a termios object. $c_iflag = $termios−>getiflag; getispeed Retrieve the input baud rate. $ispeed = $termios−>getispeed; getlflag Retrieve the c_lflag field of a termios object. $c_lflag = $termios−>getlflag; getoflag Retrieve the c_oflag field of a termios object. $c_oflag = $termios−>getoflag; getospeed Retrieve the output baud rate. $ospeed = $termios−>getospeed; setattr Set terminal control attributes. Set attributes immediately for stdout. $termios−>setattr( 1, &POSIX::TCSANOW ); Returns undef on failure. setcc 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 ); setcflag Set the c_cflag field of a termios object. $termios−>setcflag( $c_cflag | &POSIX::CLOCAL ); setiflag Set the c_iflag field of a termios object. $termios−>setiflag( $c_iflag | &POSIX::BRKINT ); setispeed Set the input baud rate. $termios−>setispeed( &POSIX::B9600 ); Returns undef on failure. setlflag Set the c_lflag field of a termios object. $termios−>setlflag( $c_lflag | &POSIX::ECHO ); setoflag Set the c_oflag field of a termios object. $termios−>setoflag( $c_oflag | &POSIX::OPOST ); setospeed Set the output baud rate. $termios−>setospeed( &POSIX::B9600 ); Returns undef on failure. Baud rate values B38400 B75 B200 B134 B300 B1800 B150 B0 B19200 B1200 B9600 B600 B4800 B50 B2400 B110 Terminal interface values TCSADRAIN TCSANOW TCOON TCIOFLUSH TCOFLUSH TCION TCIFLUSH TCSAFLUSH TCIOFF TCOOFF c_cc field values VEOF VEOL VERASE VINTR VKILL VQUIT VSUSP VSTART VSTOP VMIN VTIME NCCS c_cflag field values CLOCAL CREAD CSIZE CS5 CS6 CS7 CS8 CSTOPB HUPCL PARENB PARODD c_iflag field values BRKINT ICRNL IGNBRK IGNCR IGNPAR INLCR INPCK ISTRIP IXOFF IXON PARMRK c_lflag field values ECHO ECHOE ECHOK ECHONL ICANON IEXTEN ISIG NOFLSH TOSTOP c_oflag field values OPOST

PATHNAME CONSTANTSConstants _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 CONSTANTSConstants _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

RESOURCE CONSTANTSImported with the :sys_resource_h tag. Constants Added in Perl v5.28: PRIO_PROCESS PRIO_PGRP PRIO_USER

SYSTEM CONFIGURATIONConstants _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

ERRNOConstants E2BIG EACCES EADDRINUSE EADDRNOTAVAIL EAFNOSUPPORT EAGAIN EALREADY EBADF EBADMSG EBUSY ECANCELED ECHILD ECONNABORTED ECONNREFUSED ECONNRESET EDEADLK EDESTADDRREQ EDOM EDQUOT EEXIST EFAULT EFBIG EHOSTDOWN EHOSTUNREACH EIDRM EILSEQ EINPROGRESS EINTR EINVAL EIO EISCONN EISDIR ELOOP EMFILE EMLINK EMSGSIZE ENAMETOOLONG ENETDOWN ENETRESET ENETUNREACH ENFILE ENOBUFS ENODATA ENODEV ENOENT ENOEXEC ENOLCK ENOLINK ENOMEM ENOMSG ENOPROTOOPT ENOSPC ENOSR ENOSTR ENOSYS ENOTBLK ENOTCONN ENOTDIR ENOTEMPTY ENOTRECOVERABLE ENOTSOCK ENOTSUP ENOTTY ENXIO EOPNOTSUPP EOTHER EOVERFLOW EOWNERDEAD EPERM EPFNOSUPPORT EPIPE EPROCLIM EPROTO EPROTONOSUPPORT EPROTOTYPE ERANGE EREMOTE ERESTART EROFS ESHUTDOWN ESOCKTNOSUPPORT ESPIPE ESRCH ESTALE ETIME ETIMEDOUT ETOOMANYREFS ETXTBSY EUSERS EWOULDBLOCK EXDEV

FCNTLConstants 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

FLOATConstants 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

FLOATING-POINT ENVIRONMENTConstants FE_DOWNWARD FE_TONEAREST FE_TOWARDZERO FE_UPWARD on systems that support them.

LIMITSConstants 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

LOCALEConstants LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME LC_MESSAGES on systems that support them.

MATHConstants HUGE_VAL Added in Perl v5.22: FP_ILOGB0 FP_ILOGBNAN FP_INFINITE FP_NAN FP_NORMAL FP_SUBNORMAL FP_ZERO INFINITY NAN Inf NaN M_1_PI M_2_PI M_2_SQRTPI M_E M_LN10 M_LN2 M_LOG10E M_LOG2E M_PI M_PI_2 M_PI_4 M_SQRT1_2 M_SQRT2 on systems with C99 support.

SIGNALConstants 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 Added in Perl v5.24: ILL_ILLOPC ILL_ILLOPN ILL_ILLADR ILL_ILLTRP ILL_PRVOPC ILL_PRVREG ILL_COPROC ILL_BADSTK FPE_INTDIV FPE_INTOVF FPE_FLTDIV FPE_FLTOVF FPE_FLTUND FPE_FLTRES FPE_FLTINV FPE_FLTSUB SEGV_MAPERR SEGV_ACCERR BUS_ADRALN BUS_ADRERR BUS_OBJERR TRAP_BRKPT TRAP_TRACE CLD_EXITED CLD_KILLED CLD_DUMPED CLD_TRAPPED CLD_STOPPED CLD_CONTINUED POLL_IN POLL_OUT POLL_MSG POLL_ERR POLL_PRI POLL_HUP SI_USER SI_QUEUE SI_TIMER SI_ASYNCIO SI_MESGQ

STATConstants 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 Macros S_ISBLK S_ISCHR S_ISDIR S_ISFIFO S_ISREG

STDLIBConstants EXIT_FAILURE EXIT_SUCCESS MB_CUR_MAX RAND_MAX

STDIOConstants BUFSIZ EOF FILENAME_MAX L_ctermid L_cuserid TMP_MAX

TIMEConstants CLK_TCK CLOCKS_PER_SEC

UNISTDConstants R_OK SEEK_CUR SEEK_END SEEK_SET STDIN_FILENO STDOUT_FILENO STDERR_FILENO W_OK X_OK

WAITConstants WNOHANG WUNTRACED WNOHANG Do not suspend the calling process until a child process changes state but instead return immediately. WUNTRACED Catch stopped child processes. Macros WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIFSTOPPED WSTOPSIG WIFEXITED WIFEXITED(${^CHILD_ERROR_NATIVE}) returns true if the child process exited normally (exit() or by falling off the end of main()) WEXITSTATUS WEXITSTATUS(${^CHILD_ERROR_NATIVE}) returns the normal exit status of the child process (only meaningful if WIFEXITED(${^CHILD_ERROR_NATIVE}) is true) WIFSIGNALED WIFSIGNALED(${^CHILD_ERROR_NATIVE}) returns true if the child process terminated because of a signal WTERMSIG WTERMSIG(${^CHILD_ERROR_NATIVE}) returns the signal the child process terminated for (only meaningful if WIFSIGNALED(${^CHILD_ERROR_NATIVE}) is true) WIFSTOPPED WIFSTOPPED(${^CHILD_ERROR_NATIVE}) returns true if the child process is currently stopped (can happen only if you specified the WUNTRACED flag to waitpid()) WSTOPSIG WSTOPSIG(${^CHILD_ERROR_NATIVE}) returns the signal the child process was stopped for (only meaningful if WIFSTOPPED(${^CHILD_ERROR_NATIVE}) is true)

WINSOCK(Windows only.) Constants Added in Perl v5.24: WSAEINTR WSAEBADF WSAEACCES WSAEFAULT WSAEINVAL WSAEMFILE WSAEWOULDBLOCK WSAEINPROGRESS WSAEALREADY WSAENOTSOCK WSAEDESTADDRREQ WSAEMSGSIZE WSAEPROTOTYPE WSAENOPROTOOPT WSAEPROTONOSUPPORT WSAESOCKTNOSUPPORT WSAEOPNOTSUPP WSAEPFNOSUPPORT WSAEAFNOSUPPORT WSAEADDRINUSE WSAEADDRNOTAVAIL WSAENETDOWN WSAENETUNREACH WSAENETRESET WSAECONNABORTED WSAECONNRESET WSAENOBUFS WSAEISCONN WSAENOTCONN WSAESHUTDOWN WSAETOOMANYREFS WSAETIMEDOUT WSAECONNREFUSED WSAELOOP WSAENAMETOOLONG WSAEHOSTDOWN WSAEHOSTUNREACH WSAENOTEMPTY WSAEPROCLIM WSAEUSERS WSAEDQUOT WSAESTALE WSAEREMOTE WSAEDISCON WSAENOMORE WSAECANCELLED WSAEINVALIDPROCTABLE WSAEINVALIDPROVIDER WSAEPROVIDERFAILEDINIT WSAEREFUSED 0

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