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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.
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
Everything 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.
"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.
"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.
"asinh" This is identical to the C function "asinh()", returning the hyperbolic arcus sine of its
numerical argument [C99]. 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.
"atanh" This is identical to the C function "atanh()", returning the hyperbolic arcus tangent of its
numerical argument [C99]. 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"
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].
"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"
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].
$x_with_sign_of_y = POSIX::copysign($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"
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" 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].
"erfc" The complementary error function [C99].
"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].
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].
"fegetround"
Returns the current floating point rounding mode, one of
FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_UPWARD
"FE_TONEAREST" is like "round", "FE_TOWARDZERO" is like "trunc" [C99].
"fesetround"
Sets the floating point rounding mode, see "fegetround" [C99].
"fma" "Fused multiply-add", "x * y + z", possibly faster (and less lossy) than the explicit two
operations [C99].
my $fused = POSIX::fma($x, $y, $z);
"fmax" Maximum of "x" and "y", except when either is "NaN", returns the other [C99].
my $min = POSIX::fmax($x, $y);
"fmin" Minimum of "x" and "y", except when either is "NaN", returns the other [C99].
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.
"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.
"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].
"ilogb" Integer binary logarithm [C99]
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"
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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
You may want to use the "/\w/" construct instead.
"isalpha"
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/ ^ [[:alpha:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
"isatty"
Returns a boolean indicating whether the specified filehandle is connected to a tty. Similar to
the "-t" operator, see "-X" in perlfunc.
"iscntrl"
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/ ^ [[:cntrl:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
"isdigit"
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/ ^ [[:digit:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
You may want to use the "/\d/" construct instead.
"isfinite"
Returns true if the argument is a finite number (that is, not an infinity, or the not-a-number)
[C99].
See also "isinf", "isnan", and "fpclassify".
"isgraph"
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/ ^ [[:graph:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
"isgreater"
(Also "isgreaterequal", "isless", "islessequal", "islessgreater", "isunordered")
Floating point comparisons which handle the "NaN" [C99].
"isinf" Returns true if the argument is an infinity (positive or negative) [C99].
See also "Inf", "isnan", "isfinite", and "fpclassify".
"islower"
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/ ^ [[:lower:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
Do not use "/[a-z]/" unless you don't care about the current locale.
"isnan" Returns true if the argument is "NaN" (not-a-number) [C99].
Note that you cannot test for ""NaN"-ness" with
$x == $x
since the "NaN" is not equivalent 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].
See also "isfinite", and "fpclassify".
"isprint"
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/ ^ [[:print:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
"ispunct"
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/ ^ [[:punct:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
"isspace"
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/ ^ [[:space:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
You may want to use the "/\s/" construct instead.
"isupper"
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/ ^ [[:upper:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
Do not use "/[A-Z]/" unless you don't care about the current locale.
"isxdigit"
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/ ^ [[:xdigit:]]+ $ /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).
The function returns "TRUE" if the input string is empty, or if the corresponding C function
returns "TRUE" for every byte in the string.
"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].
See also "tgamma".
"log1p" Equivalent to "log(1 + x)", but more stable results for small argument values [C99].
"log2" Logarithm base two [C99].
See also "expm1".
"logb" Integer binary logarithm [C99].
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 current
underlying locale's formatting values. Users of this function should also read perllocale, which
provides a comprehensive discussion of Perl locale handling, including a section devoted to this
function.
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.
"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].
For the rounding mode, see "fegetround".
"lround"
Like "round", but as integer, as opposed to floating point [C99].
See also "ceil", "floor", "trunc".
"malloc"
Not implemented. "malloc()" is C-specific. Perl does memory management transparently.
"mblen" This is identical to the C function "mblen()".
Core Perl does not have any support for the wide and multibyte characters of the C standards,
except under UTF-8 locales, so this might be a rather useless function.
However, Perl supports Unicode, see perluniintro.
"mbstowcs"
This is identical to the C function "mbstowcs()".
See "mblen".
"mbtowc"
This is identical to the C function "mbtowc()".
See "mblen".
"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" Returns not-a-number [C99].
See also "isnan" and "NaN".
"nearbyint"
Returns the nearest integer to the argument, according to the current rounding mode (see
"fegetround") [C99].
"nextafter"
Returns the next representable floating point number after "x" in the direction of "y" [C99].
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].
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]
my $remainder = POSIX::remainder($x, $y)
See also "remquo".
"remove"
This is identical to Perl's builtin "unlink()" function for removing files, see "unlink" in
perlfunc.
"remquo"
Like "remainder" but also returns the low-order bits of the quotient (n) [C99]
(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].
See also "ceil", "floor", "lround", "modf", and "trunc".
"scalbn"
Returns "x * 2**y" [C99].
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"
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.)
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" );
"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 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"
Not implemented. "siglongjmp()" is C-specific: use "die" in perlfunc instead.
"signbit"
Returns zero for positive arguments, non-zero for negative arguments [C99].
"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.
"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_TIME" settings, regardless of whether or not it is
called from Perl code that is within the scope of "use locale".
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 in conjunction with the "strcoll()" function, see "strcoll".
Not really needed since Perl can do this transparently, see perllocale.
"sysconf"
Retrieves values of system configurable variables.
The following will get the machine's clock speed.
$clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );
Returns "undef" on failure.
"system"
This is identical to Perl's builtin "system()" function, see "system" in perlfunc.
"tan" This is identical to the C function "tan()", returning the tangent of the numerical argument.
See also Math::Trig.
"tanh" This is identical to the C function "tanh()", returning the hyperbolic tangent of the numerical
argument. See also Math::Trig.
"tcdrain"
This is similar to the C function "tcdrain()" for draining the output queue of its argument
stream.
Returns "undef" on failure.
"tcflow"
This is similar to the C function "tcflow()" for controlling the flow of its argument stream.
Returns "undef" on failure.
"tcflush"
This is similar to the C function "tcflush()" for flushing the I/O buffers of its argument
stream.
Returns "undef" on failure.
"tcgetpgrp"
This is identical to the C function "tcgetpgrp()" for returning the process group identifier of
the foreground process group of the controlling terminal.
"tcsendbreak"
This is similar to the C function "tcsendbreak()" for sending a break on its argument stream.
Returns "undef" on failure.
"tcsetpgrp"
This is similar to the C function "tcsetpgrp()" for setting the process group identifier of the
foreground process group of the controlling terminal.
Returns "undef" on failure.
"tgamma"
The Gamma function [C99].
See also "lgamma".
"time" This is identical to Perl's builtin "time()" function for returning the number of seconds since
the epoch (whatever it is for the system), see "time" in perlfunc.
"times" The "times()" function returns elapsed realtime since some point in the past (such as system
startup), user and system times for this process, and user and system times used by child
processes. All times are returned in clock ticks.
($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"
Returns a name for a temporary file.
$tmpfile = POSIX::tmpnam();
For security reasons, which are probably detailed in your system's documentation for the C
library "tmpnam()" function, this interface should not be used; instead see File::Temp.
"tolower"
This is identical to the C function, except that it can apply to a single character or to a whole
string, and currently operates as if the locale always is "C". Consider using the "lc()"
function, see "lc" in perlfunc, see "lc" in perlfunc, or the equivalent "\L" operator inside
doublequotish strings.
"toupper"
This is similar to the C function, except that it can apply to a single character or to a whole
string, and currently operates as if the locale always is "C". Consider using the "uc()"
function, see "uc" in perlfunc, or the equivalent "\U" operator inside doublequotish strings.
"trunc" Returns the integer toward zero from the argument [C99].
See also "ceil", "floor", and "round".
"ttyname"
This is identical to the C function "ttyname()" for returning the name of the current terminal.
"tzname"
Retrieves the time conversion information from the "tzname" variable.
POSIX::tzset();
($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";
"wcstombs"
This is identical to the C function "wcstombs()".
See "mblen".
"wctomb"
This is identical to the C function "wctomb()".
See "mblen".
"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::SigAction"
"new" 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::SigSet"
"new" 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 );
"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::Termios"
"new" 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 CONSTANTS
Constants
"_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 CONSTANTS
Constants
"_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"
SYSTEM CONFIGURATION
Constants
"_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"
ERRNO
Constants
"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"
FCNTL
Constants
"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"
FLOAT
Constants
"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 ENVIRONMENT
Constants
"FE_DOWNWARD" "FE_TONEAREST" "FE_TOWARDZERO" "FE_UPWARD" on systems that support them.
LIMITS
Constants
"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"
LOCALE
Constants
"LC_ALL" "LC_COLLATE" "LC_CTYPE" "LC_MONETARY" "LC_NUMERIC" "LC_TIME" "LC_MESSAGES" on systems
that support them.
MATH
Constants
"HUGE_VAL"
"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.
SIGNAL
Constants
"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"
STAT
Constants
"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"
STDLIB
Constants
"EXIT_FAILURE" "EXIT_SUCCESS" "MB_CUR_MAX" "RAND_MAX"
STDIO
Constants
"BUFSIZ" "EOF" "FILENAME_MAX" "L_ctermid" "L_cuserid" "L_tmpname" "TMP_MAX"
TIME
Constants
"CLK_TCK" "CLOCKS_PER_SEC"
UNISTD
Constants
"R_OK" "SEEK_CUR" "SEEK_END" "SEEK_SET" "STDIN_FILENO" "STDOUT_FILENO" "STDERR_FILENO" "W_OK"
"X_OK"
WAIT
Constants
"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)
perl v5.22.1 2020-10-19 POSIX(3perl)