/ 
POSIX-1003-0.94_3
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/ POSIX::Overview

NAME

POSIX::Overview - POSIX in Perl

DESCRIPTION

The POSIX standard defines access to the operating system. Most operating systems (not limited to the UNIX family) provide at least a part of this standard, sometimes as optional or commercial extension package.

POSIX describes how C-programmers can access the operation system. Perl's core and additional modules on CPAN together, offer most of the POSIX functionality, although usually in a more powerful way. This manual-page tries to explain where you can find POSIX features in the Perl language.

The specification

The Single UNIX Specification: Authorized Guide to Version 4 published by The Open Group is a huge specification. Issue 7 (March 2010) lists nearly 1200 functions. A large part of these functions are defined by POSIX 1003.1-2008, which gives the name to this module.

This manual page does not explain what the functions do in detail, because the official POSIX manuals do a much better job. On UNIX, those manuals are usually available as set 3p.

WARNINGS

POSIX is a standard with a long history, deeply tied into the Operating System. This means that you will encounter (sometimes large, often small) differences when used on different platforms. Perl's core and modules often attempt to hide differences, but is not always succesful.

Be warned that we refer to many modules which are not distributed with Perl's CORE, so are maintained by separate people which have their own responsibility, programming practices, and choice of license.

This manual-page attempts to be correct and complete, but might contain mistakes or lack some references. Please contribute!

How to use this manual page

For each of the POSIX functions, we try to direct you to the best documentation on how to get related functionality in Perl. Even the most simple functions will have differences. We do not explain the POSIX functions because the standard POSIX manuals do a much better job. And, of course, we do not attempt to explain core functionality or CPAN modules.

Some references are to POSIX.pm, which means that it is provided in by the POSIX module distributed with Perl itself. In all cases, when undef is returned it means failure. In that case, $! is set.

A number of references are made to modules in the POSIX::1003 name-space, often abbreviated to the last name-space component. For instance, ::FdIO stands for POSIX::1003::FdIO. Those modules give you access to all the useful POSIX.xs routine. Read POSIX::1003 for more.

Often, the description will refer you to perlfunc, which means that there is a perl core function which does similar things as the POSIX function. On most platforms you can easily find the perlfunc descriptions via perldoc. For instance:

perldoc -f open

Another important source for Operating System facts are global variables. Those are described in the perlvar manual. Those variables have extremely short names (like $$ for process-id) but also longer names ($PID and $PROCESS_ID). The latter are only available when you load the English module. Names defined by the awk programming language are amongst the long alternative names.

Finally, the tables often refer to modules which implement comparable functionality. In most cases, they offer a pure Perl (so portable) alternative.

FUNCTIONS

The functions are categorized as listed in chapter 3.3 of the book of the Open Group, with the exception of those sections which only list unsupported features.

Nothing related to threads, scheduling and tracing control is provided by Perl. See perlthrtut on the thread implementation of Perl.

  • functions beginning with posix_ are not supported

  • functions beginning with sched_ are not supported

  • functions beginning with pthread_ are not supported

  • thread-safe functions, ending on _r, are not supported

Asynchronous Input and Output Interfaces

These functions are provided by IO::AIO:

aio_cancel, aio_error, aio_fsync, aio_read, aio_return, aio_suspend,
aio_write

Not supported:

lio_listio

Jump Interfaces

These functions are used to handle error conditions. In Perl, you cannot handle these errors at such a low level.

longjmp perlfunc/die
setjmp  perlfunc/eval

Maths Library Interfaces

The accuracy of floating point numbers depends on compilation flags of Perl. At the C level, there are many versions of these functions, but only one is listed in this section.

Math::Trig provides pure perl implementations for all sine, cosine and tangent functions and their hyperbolic and reverse variants. Math::Complex provides their complex variants. In both modules, the names of the functions sometimes differ slightly from the POSIX names.

The modules Math::BigInt and Math::BigFloat offer a wide range of mathematical functions with flexible precission.

These are specified in POSIX:

acosh                           Math::Trig
acos                            ::Math
asinh                           Math::Trig
asin                            ::Math
atan2       perlfunc            ::Math
atanh                           Math::Trig
atan                            ::Math
ceil                            ::Math
cosh                            ::Math
cos         perlfunc            ::Math
exp         perlfunc            ::Math
fabs        perlfunc/abs        ::Math/abs
floor                           ::Math
fmax                            List::Util/min
fmin                            List::Util/max
fmod                            ::Math
frexp                           ::Math
isgreaterequal  perlop/>=
isgreater       perlop/>
islessequal     perlop/<=
islessgreater   perlop/!=
isless          perlop/<
ldexp                           ::Math
log10                           ::Math
log         perlfunc            ::Math
modf                            ::Math
pow         perlop/**           ::Math
rint                            ::Math
sinh                            ::Math
sin         perlfunc            ::Math
sqrt        perlfunc            ::Math
tanh                            ::Math
tan                             ::Math

Complex numbers only in Perl with Math::Complex:

cabs, cacos, cacosh, carg, casin, casinh, catan, catanh, cbrt,
ccos, ccosh, cexp, cimag, clog, conj, cpow, cproj, creal, csin,
csinh, csqrt, ctan, ctanh

Probably not supported:

copysign, erf, erfc, exp2, expm1, fdim, fma, fpclassify, hypot,
ilogb, isfinite, isinf, isnan, isnormal, isunordered, lgamma,
llround, log1p, log2, logb, lround, nan, nearbyint, nextafter,
nexttoward, remainder, remquo, round, scalbln, scalbn, signbit,
tgamma, trunc

General ISO C Library Interfaces

convert strings to values and back

All strto*, atof, atoi and friends functions are usually not needed in Perl programs: the integer and float types are at their largest size, so when a string is used in numeric context it will get converted automatically.

Still, POSIX::1003::Math does provide a few of those functions, which are sometimes more accurate in number parsing for large numbers.

strtod                          ::Math
strtol                          ::Math
strtoul                         ::Math

String handling

Perl knows about latin1 strings are utf-8 strings. Most complications of character-sets are hidden for the user, as long as the user provides encoding details at all entry and exit points of the program. See perlunicode, Encode and encoding.

strcat      perlop/.=
strchr      perlfunc/index
strcmp      perlop/cmp perlop/eq
strcpy      perlop/=
strcspn     $a =~ m/^([^$b]*)/ && length $1
strerror    perlvar/$ERRNO      ::Errno   "$!"
strlen      perlvar/length
strncat     $a .= substr $b, 0, $n;
strncmp     (substr $a, 0, $n) eq (substr $b, 0, $n)
strncpy     $a = substr $b, 0, $n;
strpbrk     $a =~ m/(.*?)[$b]/ && length $1
strrchr     $a =~ m/(.*)$b/    && length $1
strspn      $a =~ m/^([$b]*)/  && length $1
strstr      perlop/index
strtok      perlfunc/split
tolower     perlfunc/lc      "\L$str\E"  "\l$str"
toupper     perlfunc/uc      "\U$str\E"  "\u$str"

Warning: POSIX.pm provides functions named tolower and toupper, which simply call lc and uc respectively. They take their parameter as string, maybe even ut8-string, not raw ascii bytes.

sprintf and scanf

The sprintf function is provided by perlfunc, with many extensions to the POSIX format specification. Perl has powerful string interpolation features which reduce the need for sprintf.

snprintf    not needed
sprintf     perlfunc/sprintf
sscanf      use regular expressions or perlfunc/unpack
vsnprintf   not needed
vsprintf    not needed
vsscanf     not needed

Characters

POSIX.pm provides handlers of property groups, which are affected by the locale setting as long as all the characters are only single bytes. We recommend that you use regular expressions, which are more flexible. This table shows the alternative expressions.

isalnum     [[:alnum:]]   \p{Alnum}
isalpha     [[:alpha:]]   \p{Alpha}   \pL
isascii     [[:ascii:]]   \p{Ascii}
isblank     [[:blank:]]   \p{Blank}            \h
iscntrl     [[:cntrl:]]   \p{Control} \p{Cc}
isdigit     [[:digit:]]   \p{Digit}   \p{Nd}   \d
isgraph     [[:graph:]]   \p{Graph}
islower     [[:lower:]]   \p{Lower}   \p{Ll}
isprint     [[:print:]]   \p{Print}
ispunct     [[:punct:]]   \p{Punct}   \pP
isspace     [[:space:]]   \p{Space}
isupper     [[:upper:]]   \p{Upper}   \p{Lu}
isxdigit    [[:xdigit:]]  \p{XDigit}  \p{Hex}  [0-9a-fA-F]
            [[:word:]]    \p{Word}             \w

\p{PerlSpace} (\s) is close to the ASCII subdomain of \p{Space}. The \p{Word} character class is a Perl specific extension. There are hundreds more character classes and extensions. See perlunicode and perluniprops.

The isascii function is defined by XSI, not POSIX.

Locale

Locales describe national and language specific facts. See perllocale for the details.

setlocale                       ::Locale
localeconv                      ::Locale
strcoll                         POSIX.pm
strxfrm                         POSIX.pm

The functions strcoll and strxfrm are not useful in Perl, which automatically resolves character set problems.

Math

abs          perlfunc           ::Math
div                             ::Math
rand         perlfunc           ::Math
srand        perlfunc           ::Math

Integers which overflow will automatically upgrade into floats, so all abs, labs, llabs, imaxabs are implemented by "abs" in perfunc. Division via div, ldiv, lldiv, and imaxdiv are also equivalent.

The following functions where first defined by C99, and describe the handling of floating-point rounding and exceptions. They are not supported:

feclearexcept, fegetenv, fegetexceptflag, fegetround, feholdexcept,
feraiseexcept, fesetenv, fesetexceptflag, fesetround, fetestexcept,
feupdateenv

Time

The POSIX::1003::Time code provides access to all time functions. The result depends on the locale setting of the timezone. See also "Timer Interfaces".

Date::Format contains pure Perl implementations for the other functions of this section. Those are fully portable, which cannot always be said for POSIX library implementations. Also Date::Calc may be very userful.

Use Time::HiRes if you need to handle timestamps with better resolution than seconds.

asctime                         ::Time Date::Format
ctime                           ::Time Date::Format
difftime                        ::Time Time::HiRes/tv_interval
gmtime      perlfunc            ::Time Date::Calc/Gmtime
localtime   perlfunc            ::Time Date::Calc/Localtime
mktime                          ::Time Date::Calc/Mktime
strftime                        ::Time Date::Format
tzname                          ::Time  
tzset                           ::Time

Sorting

qsort       perlfunc/sort
bsearch                         POSIX::bsearch Search::Dict
                                Tree Tree::Binary

The Quick Sort implemented by qsort was used in "sort" in perlfunc uptil release 5.6. Later, it became more flexible. See the manual page about the sort pragma: sort(3pm).

Memory management

Perl uses its own reference counting memory management (of course based on the POSIX interface). Only when you write XS code, you will use abstractions of these: calloc, free, malloc and realloc.

memchr      perlfunc/index
memcmp      perlop/cmp perlop/eq
memcpy      perlop/=
memmove     perlop/substr
memset      perlop/x         $a = 'A' x 100;
offsetof    perlfunc/unpack  # removed from POSIX standard

Var-args

All functions in Perl can handle a variable list of arguments, so

va_arg      not needed
va_copy     not needed
va_end      not needed
va_start    not needed

Wide-Character ISO C Library Interfaces

The POSIX module does define wide-character functions. Wide refers to multiples bytes per character: strings able to use more than 256 different characters in an unspecified encoding. Perl itself has both single byte Latin1 and utf-8 strings, covering all needs: pick compact or powerful. One may need to use wide-characters to implement certain interface specifications, but that is getting rare.

btowc                           POSIX.pm
mblen                           POSIX.pm
mbrlen                          POSIX.pm
mbrtowc                         POSIX.pm
mbstowcs                        POSIX.pm
mbtowc                          POSIX.pm
wcstombs                        POSIX.pm
wctomb                          POSIX.pm

Not provided are all function wide versions of character classes, like iswalnum, all functions which start with tow, wcs, wct or wmem. Additionally, missing are

mbsrtowcs, mbsinit, swprintf, swscanf, vswprintf, vswscanf, wcrtomb
mbsnrtowcs, wcpcpy, wcpncpy

Also, i18n::Langinfo::Wide and POSIX::Wide offer some extras.

General C Library Extension Interfaces

Function fnmatch can usually be avoided using "glob" in perlfunc for collecting filenames in the file system. When you already have a filename in a string, you need to rewrite the pattern into a regular expression.

my @scripts = glob "*.pl";
my @scripts = grep /\.pl$/, @filenames;

Process your command-line options with Getopt::Std or Getopt::Long, which are more platform indepent and more flexible than the POSIX version (therefore they are missing) getopt, getsubopt, optarg, opterr, optind, optopt

Some string functions have simple Perl work-arounds:

strcasecmp  lc($a) cmp lc($b)
strdup      $b = $a
strncasecmp substr($a,$n) cmp substr($b,$n)
strndup     $b = substr($a, $n)
strnlen     length substr($a, $n)
stpcpy      perlop/=
stpncpy     $b = substr $a, 0, $l
strfmon                         PAB3::Utils

Clock Selection Interfaces

clock_nanosleep                 Time::HiRes

Device Input and Output Interfaces

File-descriptor based

See perlopentut section "Open a la C".

close       perlfunc/close (!)  ::FdIO/closefd
open        perlfunc/sysopen    ::FdIO/openfd
read        perlfunc/sysread    ::FdIO/readfd
write       perlfunc/syswrite   ::FdIO/writefd
pread       not supported
pwrite      not supported

File-handle based

clearerr                        IO::Handle
fclose      perlfunc/close      IO::Handle/close
fdopen      perlfunc/open       IO::Handle/new_from_fd
feof        perlfunc/eof        IO::Handle/eof
ferror      perlvar/$ERRNO      IO::Handle/error     $!+0
fflush                          IO::Handle/flush
fgetc       perlfunc/getc       IO::Handle/getc  perlfunc/read
fgets       perlfunc/readline   IO::Handle/gets      <FH>
fileno      perlfunc            IO::Handle
fopen       perlfunc/open       IO::Handle/open
fprintf     perlfunc/printf     IO::Handle/printf
fputc       perlfunc/print      IO::Handle/print
fputs       perlfunc/print      perlfunc/say  IO::Handle/say
fread       perlfunc/read
freopen     perlopentut/Re-Opening Files
fscanf      use regular expressions
fwrite      perlfunc/syswrite   IO::Handle/write
getchar     perlfunc/getc       IO::Handle/getc
getc        perlfunc            IO::Handle
gets        perlfunc/readline   IO::Handle/readline  <STDIN>
printf      perlfunc
putchar     perlfunc/print
putc        perlfunc/print
puts        perlfunc/print      perlfunc/say
scanf       use regular expressions
setbuf                          IO::Handle
setvbuf                         IO::Handle
ungetc                          IO::Handle
perror      perlfunc/warn  perlvar/$ERRNO  POSIX.pm  "$!"
stderr      *STDERR             POSIX.pm
stdin       *STDIN              POSIX.pm
stdout      *STDOUT             POSIX.pm

Event driven

Event loops require a considerable amount of file handle administration. Therefore, there are a large number of module available to support the basic calls. For instance AnyEvent, POE, IO::Multiplex, ...and many more

poll                            IO::Poll
pselect                         POSIX::pselect
select      perlfunc            ::Events IO::Select
FD_CLR                          ::Events
FD_ISSET                        ::Events
FD_SET                          ::Events
FD_ZERO                         ::Events

Extended Device Input and Output Interfaces

Where Perl always uses flexible lists, the followin are not adding anything. See "open" in perlfunc

vfprintf       perlfunc/printf
vprintf        (same)
vfscanf        use regex
vscanf         (same)
dprintf        write $fd, sprintf $fmt, @data
vdprint        (same)
fmemopen       open $fh, '>', \$buffer;
open_memstream (same)

General Terminal Interfaces

Most terminal interface functions are provided by the separate POSIX::1003::Termios module, which is the same as the POSIX::Termios component in POSIX.pm See its manpage for the usage.

cfgetispeed                     ::Termios
cfgetospeed                     ::Termios
cfsetispeed                     ::Termios
cfsetospeed                     ::Termios
ctermid                         ::Proc
isatty         perlfunc/-X flag -t
tcdrain                         ::Termios
tcflow                          ::Termios
tcflush                         ::Termios
tcgetattr                       ::Termios/getattr
tcsendbreak                     ::Termios
tcsetattr                       ::Termios/setattr
ttyname                         ::Termios

Dynamic Linking Interfaces

The loading of shared libraries in organized by its XS wrapper. The module XSLoader opens both the wrapper and the wrapped library. Therefore, there is no need for

dlclose, dlerror, dlopen, dlsym

File Descriptor Management Interfaces

Although the name of this section suggests differently, actually most of these functions use a file handle, not a descriptor.

On file handles:

fcntl       perlfunc            ::Fcntl Fcntl.pm
fgetpos     perlfunc/tell       IO::Seekable/getpos
fseek       perlfunc/seek       IO::Seekable/seek
fseeko      perlfunc/seek       IO::Seekable/seek
fsetpos     perlfunc/seek       IO::Seekable/setpos
ftell       perlfunc/tell       IO::Seekable/tell
ftello      perlfunc/tell       IO::Seekable/tell
ftruncate   perlfunc/truncate   IO::Handle/truncate
rewind      POSIX.pm

Using file-descriptors

dup         perlopentut/<&=     ::FdIO/dupfd
dup2                            ::FdIO/dup2fd
lseek                           ::FdIO/seekfd

FIFO Interfaces

mkfifo                          ::FS
mkfifoat    not supported
mknodat     not supported

File Attribute Interfaces

Perl's chown and chmod accept both file names and file handles. Be warned that the order of the parameters is different!

chmod       perlfunc
chown       perlfunc
fchmod      perlfunc/chmod
fchown      perlfunc/chown
umask       perlfunc
fchmodat    not supported
fchownat    not supported

The symbolic constants for chmod are provided by Fcntl (and POSIX.pm)

Thread-Safe Stdio Locking Interfaces

Perl does support the non-portable flock (see "flock" in perlfunc) in core, but the POSIX flockfile mechanism is probably unsupported:

flockfile, ftrylockfile, funlockfile, getc_unlocked,
getchar_unlocked, putc_unlocked, putchar_unlocked

File System Interfaces

access      filetest            ::FS
chdir       perlfunc      
closedir    perlfunc            IO::Dir/close
creat       perlfunc/sysopen    ::FdIO/creatfd
fchdir      perlfunc         
fpathconf                       ::Pathconf
fstat       perlfunc/stat       File::stat POSIX.pm
fstatvfs                        Filesys::statvfs
getcwd                          Cwd/getcwd
link        perlfunc         
mkdir       perlfunc         
mkstemp                         File::Temp/mkstemp
opendir     perlfunc            IO::Dir/open
pathconf                        ::Pathconf
readdir     perlfunc            IO::Dir/read
remove                          File::Remove  POSIX.pm
rename      perlfunc         
rewinddir   perlfunc            IO::Dir/rewind
rmdir       perlfunc
stat        perlfunc            File::stat
statvfs                         Filesys::statvfs
tmpfile                         File::Temp IO::File/new_tmpfile
tmpnam      (insecure!)         File::Temp POSIX.pm
truncate    perlfunc
unlink      perlfunc       
utime       perlfunc            ::FS POSIX.pm

Warning:

POSIX::utime($filename, $atime, $mtime);
CORE::utime($atime, $mtime, @filenames);

The symbolic constants needed to understand the result of stat are provided by Fcntl.

File System Extension Interfaces

alphasort   perlfunc/sort
getdelim    perlvar/$INPUT_RECORD_SEPARATOR
getline     $a = <FH>           IO::Handle
glob        perlfunc/glob
globfree    never needed
mkdtemp     File::Temp/mkdtemp
scandir     perlfunc/glob
dirfd       not supported
fdopendir   not supported

None of the functions of the 'at' interface is supported: they provide a way to use paths relative to a file-descriptor. This POSIX module only supports their absolute brothers:

faccessat, fstatat, linkat, mkdirat, openat, renameat,
unlinkat, utimensat

Internationalization Interfaces

nl_langinfo                     I18N::Langinfo/langinfo

This interface is far to simple to really translate messages into various languages. You may have a look at various implementations of gettext.

catclose                        Locale::Msgcat
catgets                         Locale::Msgcat
catopen                         Locale::Msgcat

An Object Oriented wrapper to the iconv interface is provided by Text::Iconv. Better have a look at the Encode first.

iconv                           Text::Iconv/convert
iconv_open                      Text::Iconv/new
iconv_close                     Text::Iconv/DESTROY

Job Control Interfaces

setpgid                         ::Proc
tcgetpgrp                       ::Proc
tcsetpgrp                       ::Proc
tcgetsid    not supported

Memory Interfaces

Memory management is done by the language. It is difficult to allocate data structures on specific locations, although there are various mmap interfaces.

mmap                            Sys::Mmap   Mmap
munmap                          Sys::Mmap   Mmap
mprotect                        IO::AIO/aio_mprotect

Multiple Concurrent Locale Interfaces

The functions newlocale, uselocale, duplocale, and freelocale are not supported. Neither are all of the functions which relate to is, all ending on _l, like isalnum_l().

Multiple Process Interfaces

_Exit                           ::Proc/_exit
_exit                           ::Proc
assert        Carp/croak        POSIX.pm
atexit        perlsub/END{} block
clock                           ::Time Time::HiRes
exec*         perlfunc
exit          perlfunc
fork          perlfunc          Windows::perlfork
getpgrp       perlfunc    
getpgid                         ::Proc
getpid        perlvar/$PID  $$
getppid       perlvar/$PPID
getsid        not supported
setsid                          ::Proc
sleep         perlfunc          POSIX.pm (see warning)
times         perlfunc          ::Proc/times5
wait          perlfunc          ::Proc
waitid        not supported
waitpid       perlfunc          ::Proc
fexecve       not supported

Warning, different return parameters for POSIX.pm

         ($user, $sys, $cuser, $csys) = CORE::times();
($elapse, $user, $sys, $cuser, $csys) = POSIX::times();
($elapse, $user, $sys, $cuser, $csys) = ::Proc::times5();

Warning, different return value for POSIX.pm

$slept = CORE::sleep(10);
$early = POSIX::sleep(10); # $slept+$early=10

$pid   = waitpid(-1, WNOHANG);

Networking Interfaces

handling sockets

Most code uses the Object Oriented approach via IO::Socket::INET.

accept      perlfunc            IO::Socket
bind        perlfunc            IO::Socket
connect     perlfunc            IO::Socket::INET
getsockname perlfunc            IO::Socket/sockname
getpeername perlfunc            IO::Socket/peername
getsockopt  perlfunc            IO::Socket/sockopt
setsockopt  perlfunc            IO::Socket/sockopt
shutdown    perlfunc            IO::Socket
socket      perlfunc            IO::Socket
sockatmark                      IO::Socket/atmark
socketpair  perlfunc            IO::Socket
listen      perlfunc            IO::Socket
recv        perlfunc            IO::Socket
recvfrom    perlfunc/rev        IO::Socket/recv
recvmsg     not supported
send        perlfunc            IO::Socket
sendmsg     not supported
sendto      perlfunc/send       IO::Socket/send

If you use the right functions of IO::Socket::INET you will not need these. Otherwise, you should take a look at "pack" in perlfunc and unpack.

htonl, htons, ntohl, ntohs
inet_addr, inet_ntoa, inet_ntop, inet_pton

network configuration

Most network configuration functions are provided in CORE. There are also object wrappers in various Net:: modules.

getaddrinfo      perlfunc       Net::addrinfo
gethostbyaddr    perlfunc       Net::hostent
gethostbyname    perlfunc       Net::hostent
gethostent       perlfunc       Net::hostent
gethostname                     Sys::Hostname
getnameinfo      perlfunc
getnetbyaddr     perlfunc       Net::netent
getnetbyname     perlfunc       Net::netent
getnetent        perlfunc       Net::netent
getprotobyname   perlfunc       Net::protoent
getprotobynumber perlfunc       Net::protoent
getprotoent      perlfunc       Net::protoent
getservbyname    perlfunc       Net::servent
getservbyport    perlfunc       Net::servent
getservent       perlfunc       Net::servent
sethostent       perlfunc       Net::hostent
setnetent        perlfunc       Net::netent
setprotoent      perlfunc       Net::protoent
setservent       perlfunc       Net::servent

Never needed, memory automatically freed:

endhostent, endnetent, endprotoent, endservent, freeaddrinfo,
if_freenameindex

Not supported:

gai_strerror, if_indextoname, if_nameindex, if_nametoindex

Pipe Interfaces

The pipe has an implementation in POSIX.pm, which uses file descriptors. The CORE version of pipe uses file handles.

pipe        perlfunc            ::FdIO/pipefd

Warning, different return parameters for POSIX.pm

my ($r_fh, $w_fh) = CORE::pipe();
my ($r_fd, $w_fd) = POSIX::pipe();
my ($r_fd, $w_fd) = ::FdIO::pipefd();

Realtime Signal Interfaces

sigqueue                        POSIX::RT::Signal
sigtimedwait                    POSIX::RT::Signal
sigwaitinfo                     POSIX::RT::Signal

Regular Expression Interfaces

Perl's regular expressions are much more powerful. See perlre.

regcomp     qr//
regerror    not needed
regexec     perlop/=~
regfree     not needed

Semaphore Interfaces

POSIX semaphores are supported by POSIX::RT::Semaphore:

sem_close                       POSIX::RT::Semaphore/close
sem_destroy                     POSIX::RT::Semaphore/destroy
sem_getvalue                    POSIX::RT::Semaphore/getvalue
sem_init                        POSIX::RT::Semaphore/init
sem_open                        POSIX::RT::Semaphore/open
sem_post                        POSIX::RT::Semaphore/post
sem_timedwait                   POSIX::RT::Semaphore/timedwait
sem_trywait                     POSIX::RT::Semaphore/trywait
sem_unlink                      POSIX::RT::Semaphore/unlink
sem_wait                        POSIX::RT::Semaphore/wait

Shell and Utilities Interfaces

pclose       perlfunc/close
popen        perlfunc/open ('|-' or '-|')  perlfunc/qx
system       perlfunc
wordexp      perlfunc/glob
wordfree     never needed

Signal Interfaces

Signal handling is provided via POSIX::1003:SigAction and POSIX::SigSet. Take a look at those manuals.

abort        perlvar/%SIG
alarm        perlfunc
kill         perlfunc           ::Signals
pause                           ::Signals
psiginfo     not supported
psignal      not supported
raise                           ::Signals
sigaction                       ::Signals
sigaddset                       ::Signals
sigdelset                       ::Signals
sigemptyset                     ::Signals
sigfillset                      ::Signals
sigismember                     ::Signals
signal       perlvar/%SIG       ::Signals
sigpending                      ::Signals
sigprocmask                     ::Signals
sigsuspend                      ::Signals
sigwait      not supported
strsignal                       ::Signals

Warning, parameter order in POSIX.pm

CORE::kill($signal, $pid);
::Signals::kill($signal, $pid);
POSIX::kill($pid, $signal);

Single Process Interfaces

confstr                         ::Confstr
environ     perlvar/%ENV
errno       perlvar/$ERRNO      $!+0
getenv      perlvar/%ENV        $ENV{PATH}
setenv      perlvar/%ENV        $ENV{HOME} = '/tmp'
sysconf                         ::Sysconf
uname                           ::OS
unsetenv    perlvar/%ENV        delete $ENV{PS1}

The error constants are provided by Errno.

lchown                          ::FS
lstat       perlfunc
readlinkat  not supported
readlink    perlfunc
symlinkat   not supported
symlink     perlfunc

Warning, POSIX.pm accepts only one filename

CORE::chown($uid, $gid, @filename);
::FS::lchown($uid, $gid, @symlinks);
POSIX::lchown($uid, $gid, $symlink); # !!!

System Database Interfaces

getgrgid    perlfunc            User::grent
getgrnam    perlfunc            User::grent
getpwnam    perlfunc            User::pwent
getpwuid    perlfunc            User::pwent

Timer Interfaces

clock_getres                    Time::HiRes POSIX::RT::Clock
clock_gettime                   Time::HiRes POSIX::RT::Clock
clock_settime                   Time::HiRes POSIX::RT::Clock
nanosleep                       Time::HiRes POSIX::RT::Clock
timer_create                    POSIX::RT::Timer
timer_delete                    POSIX::RT::Timer
timer_getoverrun                POSIX::RT::Timer
timer_gettime                   POSIX::RT::Timer
timer_settime                   POSIX::RT::Timer

User and Group Interfaces

Expect portability issues on this subject. Better not use any of these, but use the abstract POSIX::User instead!

cuserid                         ::Proc
getegid     perlvar/$EGID $)    ::User
geteuid     perlvar/$EUID $>    ::User
getgid      perlvar/$GID  $(    ::User
getgroups   perlvar/$GID  $(    ::User
getlogin    perlfunc            ::User
getuid      perlvar/$UID  $<    ::User    # warning
setegid     perlvar/$EGID $)    ::User    # warning
seteuid     perlvar/$EUID $>    ::User    # warning
setgid      perlvar/$GID  $(    ::User    # warning
setuid      perlvar/$UID  $<    ::User    # warning

Warning: The special variables for user- and group-ids try to be smart: they are implemented using getreuid and/or friends. POSIX.pm provides setuid and setgid which simply call the special variables. So: both do not offer access to the system functions with that name.

Wide Character Device Input and Output Interfaces

No useful support for wide characters, so no

fgetwc, fgetws, fputwc, fputws, fwide, fwprintf, fwscanf,
getwc, getwchar, putwc, putwchar, ungetwc, vfwprintf, vfwscanf,
vwprintf, vwscanf, wprintf, wscanf

Process CPU-Time Clocks Interfaces

Probably unsupported:

clock_getcpuclockid             POSIX::RT::Clock/get_cpuclock

File Synchronization Interfaces

fsync                           IO::Handle/sync File::Sync

Memory Locking Interfaces

mlockall                        IO::AIO
munlockall                      IO::AIO
mlock                           IO::AIO
munlock                         IO::AIO

Message Passing Interfaces

mq_close                        POSIX::RT::MQ
mq_getattr                      POSIX::RT::MQ
mq_notify                       POSIX::RT::MQ
mq_open                         POSIX::RT::MQ
mq_receive                      POSIX::RT::MQ
mq_send                         POSIX::RT::MQ
mq_setattr                      POSIX::RT::MQ
mq_timedreceive                 POSIX::RT::MQ
mq_timedsend                    POSIX::RT::MQ
mq_unlink                       POSIX::RT::MQ

Shared Memory Objects Interfaces

shm_open                        POSIX::RT:SharedMem
shm_unlink                      POSIX::RT:SharedMem

Synchronized Input and Output Interfaces

fdatasync                       IO::AIO/aio_fdatasync
msync                           IO::AIO/aio_msync

Trace Event Filter Interfaces

No tracing support on POSIX level via posix_trace. There are various ways to debug Perl, however. For instance try

perl -s script.pl

XSI General C Library Interfaces

Comparible functionality for functions which never made it into POSIX:

a64l                            MIME::Base64/encode
daylight                        ::Time/tzname
ffs          perlfunc/vec
getdate                         ::Time/strftime
isascii      perlre/ [[:ascii:]]  \p{Ascii}
l64a                            MIME::Base64/decode
memccpy      $b = $1 if $a =~ m/(.*{,n}?)(?:c|$)/
signgam      math, probably not supported
strptime                        Time::Piece
swab         ($b,$a) = ($a,$b)
timezone                        ::Time/tzname
toascii      $c & 0x7f
_tolower     perlfunc/lc
_toupper     perlfunc/lu

No support for alternative random generators

drand48, erand48, jrand48, lcong48, lrand48, mrand48, nrand48,
seed48, srand48, initstate, random, setstate, srandom

Perl supports HASHes by itself, so no need for

hcreate, hdestroy, hsearch

No need for double linked lists and table management

insque, remque, lfind, lsearch

Binary trees are less efficient than HASHes, which are much simpler to use as well. You may take a look at Tree or Tree::Binary, because these are missing:

tdelete, tfind, tsearch, twalk

XSI Database Management Interfaces

Some simple database which probably no-one uses anymore. See DBI, for instance DBI::DBM.

dbm_clearerr, dbm_close, dbm_delete, dbm_error, dbm_fetch,
dbm_firstkey, dbm_nextkey, dbm_open, dbm_store

XSI Device Input and Output Interfaces

fmtmsg                          Sys::Syslog

Probably not supported:

grantpt, posix_openpt, ptsname, readv, unlockpt, write

XSI File System Interfaces

basename                        File::Basename
dirname                         File::Basename
ftw                             File::Find/find
lockf        			  File::lockf
mknod                           ::FS Unix::Mknod Mknod
nftw                            File::Find/find
realpath                        File::Spec/canonpath
seekdir      perlfunc           IO::Dir/seek
sync                            File::Sync
telldir      perlfunc           IO::Dir/tell
tempnam      (insecure!)        File::Temp

XSI Interprocess Communication Interfaces

ftok                            IPC::SysV IPC::SharedMem
msgctl                          IPC::Msg
msgget                          IPC::Msg
msgrcv                          IPC::Msg
msgsnd                          IPC::Msg
semctl                          IPC::Semaphore
semget                          IPC::Semaphore
semop                           IPC::Semaphore
shmat                           IPC::SysV IPC::SharedMem
shmctl                          IPC::SysV IPC::SharedMem
shmdt                           IPC::SysV IPC::SharedMem
shmget                          IPC::SysV IPC::SharedMem

XSI Jump Interfaces

No _longjmp nor _setjmp.

XSI Maths Library Interfaces

No j0, j1, jn, y0, y1, yn

XSI Multiple Process Interfaces

getpriority  perlfunc           BSD::Resource
getrlimit                       ::Limit BSD::Resource
getrusage                       Unix::Getrusage BSD::Resource
nice                            ::Proc
setpgrp      perlfunc           ::Proc
setpriority  perlfunc           BSD::Resource
setrlimit                       ::Limit BSD::Resource
ulimit                          ::Limit

XSI Signal Interfaces

The XSI signal interface is not supported, so no

killpg, sigaltstack, sighold, sigignore, siginterrupt, sigpause,
sigrelse, sigset

XSI Single Process Interfaces

gethostid    not supported
gettimeofday                    Time::HiRes
putenv       perlvar/%ENV

XSI System Logging Interfaces

closelog                        Sys::Syslog
openlog                         Sys::Syslog
setlogmask                      Sys::Syslog
syslog                          Sys::Syslog

See also the many logging frameworks, like Log::Log4perl, Log::Dispatch, or Log::Report.

XSI Timer Interfaces

getitimer                       Time::HiRes
setitimer                       Time::HiRes

XSI User and Group Interfaces

endgrent     not needed
endpwent     not needed
endutxent                       User::Utmp
getgrent     perlfunc           User::grent
getpwent     perlfunc           User::pwent
getutxent                       User::Utmp
getutxid                        User::Utmp
getutxline                      User::Utmp
pututxline                      User::Utmp
setgrent     perlfunc           User::grent
setpwent     perlfunc           User::pwent
setregid     perlvar/$GID,$EGID ::User
setreuid     perlvar/$UID,$EUID ::User
setutxent                       User::Utmp

Non-standard, but commonly available. See also POSIX::User.

getresgid                       ::User
getresuid                       ::User
setresgid                       ::User
setresuid                       ::User

XSI STREAMS Interfaces

ioctl        perlfunc

Streams are not supported. So no:

fattach, fdetach, getmsg, getpmsg, isastream, putmsg, putpmsg

CONSTANTS

POSIX also defines zillions of constants. They are listed in (and available via) the POSIX::1003 modules. The _POSIX_ constants can be read via POSIX::1003::Properties.

SEE ALSO

This module is part of POSIX-1003 distribution version 0.94_3, built on June 10, 2013. Website: http://perl.overmeer.net. The code is based on POSIX, which is released with Perl itself. See also POSIX::Util for additional functionality.

COPYRIGHTS

Copyrights 2011-2013 on the perl code and the related documentation by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See http://www.perl.com/perl/misc/Artistic.html