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 the perlfunc  manpage
 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.
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.
- 
_exit
- 
This is identical to the C function 
_exit()
.
 
- 
abort
- 
This is identical to the C function 
abort()
.
 
- 
abs
- 
This is identical to Perl's builtin 
abs()
 function.
 
- 
access
- 
Determines the accessibility of a file.
 if( POSIX::access( "/", &POSIX::R_OK ) ){
                print "have read permission\n";
        }Returns undefon failure.
 
 
- 
acos
- 
This is identical to the C function 
acos()
.
 
- 
alarm
- 
This is identical to Perl's builtin 
alarm()
 function.
 
- 
asctime
- 
This is identical to the C function 
asctime()
.
 
- 
asin
- 
This is identical to the C function 
asin()
.
 
- 
assert
- 
Unimplemented.
 
- 
atan
- 
This is identical to the C function 
atan()
.
 
- 
atan2
- 
This is identical to Perl's builtin 
atan2()
 function.
 
- 
atexit
- 
atexit()
 is C-specific: use END {} instead.
 
- 
atof
- 
atof()
 is C-specific.
 
- 
atoi
- 
atoi()
 is C-specific.
 
- 
atol
- 
atol()
 is C-specific.
 
- 
bsearch
- 
bsearch()
 not supplied.
 
- 
calloc
- 
calloc()
 is C-specific.
 
- 
ceil
- 
This is identical to the C function 
ceil()
.
 
- 
chdir
- 
This is identical to Perl's builtin 
chdir()
 function.
 
- 
chmod
- 
This is identical to Perl's builtin 
chmod()
 function.
 
- 
chown
- 
This is identical to Perl's builtin 
chown()
 function.
 
- 
clearerr
- 
Use method 
FileHandle::
clearerr()
 instead.
 
- 
clock
- 
This is identical to the C function 
clock()
.
 
- 
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 undefon failure.
 
 
- 
closedir
- 
This is identical to Perl's builtin 
closedir()
 function.
 
- 
cos
- 
This is identical to Perl's builtin 
cos()
 function.
 
- 
cosh
- 
This is identical to the C function 
cosh()
.
 
- 
creat
- 
Create a new file.  This returns a file descriptor like the ones returned by
POSIX::open.  UsePOSIX::closeto close the file.
 $fd = POSIX::creat( "foo", 0611 );
        POSIX::close( $fd );
 
- 
ctermid
- 
Generates the path name for the controlling terminal.
 $path = POSIX::ctermid();
 
- 
ctime
- 
This is identical to the C function 
ctime()
.
 
- 
cuserid
- 
Get the character login name of the user.
 $name = POSIX::cuserid();
 
- 
difftime
- 
This is identical to the C function 
difftime()
.
 
- 
div
- 
div()
 is C-specific.
 
- 
dup
- 
This is similar to the C function 
dup()
.
This uses file descriptors such as those obtained by calling
POSIX::open.
 Returns undefon failure.
 
 
- 
dup2
- 
This is similar to the C function 
dup2()
.
This uses file descriptors such as those obtained by calling
POSIX::open.
 Returns undefon failure.
 
 
- 
errno
- 
Returns the value of errno.
 $errno = POSIX::errno();
 
- 
execl
- 
execl()
 is C-specific.
 
- 
execle
- 
execle()
 is C-specific.
 
- 
execlp
- 
execlp()
 is C-specific.
 
- 
execv
- 
execv()
 is C-specific.
 
- 
execve
- 
execve()
 is C-specific.
 
- 
execvp
- 
execvp()
 is C-specific.
 
- 
exit
- 
This is identical to Perl's builtin 
exit()
 function.
 
- 
exp
- 
This is identical to Perl's builtin 
exp()
 function.
 
- 
fabs
- 
This is identical to Perl's builtin 
abs()
 function.
 
- 
fclose
- 
Use method 
FileHandle::
close()
 instead.
 
- 
fcntl
- 
This is identical to Perl's builtin 
fcntl()
 function.
 
- 
fdopen
- 
Use method 
FileHandle::
new_from_fd()
 instead.
 
- 
feof
- 
Use method 
FileHandle::
eof()
 instead.
 
- 
ferror
- 
Use method 
FileHandle::
error()
 instead.
 
- 
fflush
- 
Use method 
FileHandle::
flush()
 instead.
 
- 
fgetc
- 
Use method 
FileHandle::
getc()
 instead.
 
- 
fgetpos
- 
Use method 
FileHandle::
getpos()
 instead.
 
- 
fgets
- 
Use method 
FileHandle::
gets()
 instead.
 
- 
fileno
- 
Use method 
FileHandle::
fileno()
 instead.
 
- 
floor
- 
This is identical to the C function 
floor()
.
 
- 
fmod
- 
This is identical to the C function 
fmod()
.
 
- 
fopen
- 
Use method 
FileHandle::
open()
 instead.
 
- 
fork
- 
This is identical to Perl's builtin 
fork()
 function.
 
- 
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 /tmp/foo.
 
 $fd = POSIX::open( "/tmp/foo", &POSIX::O_RDONLY );
        $path_max = POSIX::fpathconf( $fd, &POSIX::_PC_PATH_MAX );Returns undefon failure.
 
 
- 
fprintf
- 
fprintf()
 is C-specific--use printf instead.
 
- 
fputc
- 
fputc()
 is C-specific--use print instead.
 
- 
fputs
- 
fputs()
 is C-specific--use print instead.
 
- 
fread
- 
fread()
 is C-specific--use read instead.
 
- 
free
- 
free()
 is C-specific.
 
- 
freopen
- 
freopen()
 is C-specific--use open instead.
 
- 
frexp
- 
Return the mantissa and exponent of a floating-point number.
 ($mantissa, $exponent) = POSIX::frexp( 3.14 );
 
- 
fscanf
- 
fscanf()
 is C-specific--use <> and regular expressions instead.
 
- 
fseek
- 
Use method 
FileHandle::
seek()
 instead.
 
- 
fsetpos
- 
Use method 
FileHandle::
setpos()
 instead.
 
- 
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 );
 
- 
ftell
- 
Use method 
FileHandle::
tell()
 instead.
 
- 
fwrite
- 
fwrite()
 is C-specific--use print instead.
 
- 
getc
- 
This is identical to Perl's builtin 
getc()
 function.
 
- 
getchar
- 
Returns one character from STDIN.
 
- 
getcwd
- 
Returns the name of the current working directory.
 
- 
getegid
- 
Returns the effective group id.
 
- 
getenv
- 
Returns the value of the specified enironment variable.
 
- 
geteuid
- 
Returns the effective user id.
 
- 
getgid
- 
Returns the user's real group id.
 
- 
getgrgid
- 
This is identical to Perl's builtin 
getgrgid()
 function.
 
- 
getgrnam
- 
This is identical to Perl's builtin 
getgrnam()
 function.
 
- 
getgroups
- 
Returns the ids of the user's supplementary groups.
 
- 
getlogin
- 
This is identical to Perl's builtin 
getlogin()
 function.
 
- 
getpgrp
- 
This is identical to Perl's builtin 
getpgrp()
 function.
 
- 
getpid
- 
Returns the process's id.
 
- 
getppid
- 
This is identical to Perl's builtin 
getppid()
 function.
 
- 
getpwnam
- 
This is identical to Perl's builtin 
getpwnam()
 function.
 
- 
getpwuid
- 
This is identical to Perl's builtin 
getpwuid()
 function.
 
- 
gets
- 
Returns one line from STDIN.
 
- 
getuid
- 
Returns the user's id.
 
- 
gmtime
- 
This is identical to Perl's builtin 
gmtime()
 function.
 
- 
isalnum
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isalpha
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isatty
- 
Returns a boolean indicating whether the specified filehandle is connected
to a tty.
 
- 
iscntrl
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isdigit
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isgraph
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
islower
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isprint
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
ispunct
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isspace
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isupper
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
isxdigit
- 
This is identical to the C function, except that it can apply to a single
character or to a whole string.
 
- 
kill
- 
This is identical to Perl's builtin 
kill()
 function.
 
- 
labs
- 
labs()
 is C-specific, use abs instead.
 
- 
ldexp
- 
This is identical to the C function 
ldexp()
.
 
- 
ldiv
- 
ldiv()
 is C-specific, use / and int instead.
 
- 
link
- 
This is identical to Perl's builtin 
link()
 function.
 
- 
localeconv
- 
Get numeric formatting information.  Returns a reference to a hash
containing the current locale formatting values.
The database for the de (Deutsch or German) locale.
 
 $loc = POSIX::setlocale( &POSIX::LC_ALL, "de" );
        print "Locale = $loc\n";
        $lconv = POSIX::localeconv();
        print "decimal_point    = ", $lconv->{decimal_point},   "\n";
        print "thousands_sep    = ", $lconv->{thousands_sep},   "\n";
        print "grouping = ", $lconv->{grouping},        "\n";
        print "int_curr_symbol  = ", $lconv->{int_curr_symbol}, "\n";
        print "currency_symbol  = ", $lconv->{currency_symbol}, "\n";
        print "mon_decimal_point = ", $lconv->{mon_decimal_point}, "\n";
        print "mon_thousands_sep = ", $lconv->{mon_thousands_sep}, "\n";
        print "mon_grouping     = ", $lconv->{mon_grouping},    "\n";
        print "positive_sign    = ", $lconv->{positive_sign},   "\n";
        print "negative_sign    = ", $lconv->{negative_sign},   "\n";
        print "int_frac_digits  = ", $lconv->{int_frac_digits}, "\n";
        print "frac_digits      = ", $lconv->{frac_digits},     "\n";
        print "p_cs_precedes    = ", $lconv->{p_cs_precedes},   "\n";
        print "p_sep_by_space   = ", $lconv->{p_sep_by_space},  "\n";
        print "n_cs_precedes    = ", $lconv->{n_cs_precedes},   "\n";
        print "n_sep_by_space   = ", $lconv->{n_sep_by_space},  "\n";
        print "p_sign_posn      = ", $lconv->{p_sign_posn},     "\n";
        print "n_sign_posn      = ", $lconv->{n_sign_posn},     "\n";
 
- 
localtime
- 
This is identical to Perl's builtin 
localtime()
 function.
 
- 
log
- 
This is identical to Perl's builtin 
log()
 function.
 
- 
log10
- 
This is identical to the C function 
log10()
.
 
- 
longjmp
- 
longjmp()
 is C-specific: use die instead.
 
- 
lseek
- 
Move the read/write file pointer.  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 undefon failure.
 
 
- 
malloc
- 
malloc()
 is C-specific.
 
- 
mblen
- 
This is identical to the C function 
mblen()
.
 
- 
mbstowcs
- 
This is identical to the C function 
mbstowcs()
.
 
- 
mbtowc
- 
This is identical to the C function 
mbtowc()
.
 
- 
memchr
- 
memchr()
 is C-specific, use index() instead.
 
- 
memcmp
- 
memcmp()
 is C-specific, use eq instead.
 
- 
memcpy
- 
memcpy()
 is C-specific, use = instead.
 
- 
memmove
- 
memmove()
 is C-specific, use = instead.
 
- 
memset
- 
memset()
 is C-specific, use x instead.
 
- 
mkdir
- 
This is identical to Perl's builtin 
mkdir()
 function.
 
- 
mkfifo
- 
This is similar to the C function 
mkfifo()
.
Returns undefon failure.
 
 
- 
mktime
- 
Convert date/time info to a calendar time.
Synopsis:
 
 mktime(sec, min, hour, mday, mon, year, wday = 0, yday = 0, isdst = 0)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 undefon failure.
 
 
- 
modf
- 
Return the integral and fractional parts of a floating-point number.
 ($fractional, $integral) = POSIX::modf( 3.14 );
 
- 
nice
- 
This is similar to the C function 
nice()
.
Returns undefon failure.
 
 
- 
offsetof
- 
offsetof()
 is C-specific.
 
- 
open
- 
Open a file for reading for writing.  This returns file descriptors, not
Perl filehandles.  Use POSIX::closeto 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 undefon failure.
 
 
- 
opendir
- 
Open a directory for reading.
 $dir = POSIX::opendir( "/tmp" );
        @files = POSIX::readdir( $dir );
        POSIX::closedir( $dir );Returns undefon 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 /tmp.
 
 $path_max = POSIX::pathconf( "/tmp", &POSIX::_PC_PATH_MAX );Returns undefon failure.
 
 
- 
pause
- 
This is similar to the C function 
pause()
.
Returns undefon failure.
 
 
- 
perror
- 
This is identical to the C function 
perror()
.
 
- 
pipe
- 
Create an interprocess channel.  This returns file descriptors like those
returned by POSIX::open.
 ($fd0, $fd1) = POSIX::pipe();
        POSIX::write( $fd0, "hello", 5 );
        POSIX::read( $fd1, $buf, 5 );
 
- 
pow
- 
Computes $x raised to the power $exponent.
 $ret = POSIX::pow( $x, $exponent );
 
- 
printf
- 
Prints the specified arguments to STDOUT.
 
- 
putc
- 
putc()
 is C-specific--use print instead.
 
- 
putchar
- 
putchar()
 is C-specific--use print instead.
 
- 
puts
- 
puts()
 is C-specific--use print instead.
 
- 
qsort
- 
qsort()
 is C-specific, use sort instead.
 
- 
raise
- 
Sends the specified signal to the current process.
 
- 
rand
- 
rand()
 is non-portable, use Perl's rand instead.
 
- 
read
- 
Read from a file.  This uses file descriptors such as those obtained by
calling POSIX::open.  If the buffer$bufis 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 undefon failure.
 
 
- 
readdir
- 
This is identical to Perl's builtin 
readdir()
 function.
 
- 
realloc
- 
realloc()
 is C-specific.
 
- 
remove
- 
This is identical to Perl's builtin 
unlink()
 function.
 
- 
rename
- 
This is identical to Perl's builtin 
rename()
 function.
 
- 
rewind
- 
Seeks to the beginning of the file.
 
- 
rewinddir
- 
This is identical to Perl's builtin 
rewinddir()
 function.
 
- 
rmdir
- 
This is identical to Perl's builtin 
rmdir()
 function.
 
- 
scanf
- 
scanf()
 is C-specific--use <> and regular expressions instead.
 
- 
setgid
- 
Sets the real group id for this process.
 
- 
setjmp
- 
setjmp()
 is C-specific: use eval {} instead.
 
- 
setlocale
- 
Modifies and queries program's locale.
The following will set the traditional UNIX system locale behavior.
 
 $loc = POSIX::setlocale( &POSIX::LC_ALL, "C" );
 
- 
setpgid
- 
This is similar to the C function 
setpgid()
.
Returns undefon failure.
 
 
- 
setsid
- 
This is identical to the C function 
setsid()
.
 
- 
setuid
- 
Sets the real user id for this process.
 
- 
sigaction
- 
Detailed signal management.  This uses 
POSIX::SigAction
 objects for the
actionandoldactionarguments.  Consult your system's 
sigaction
manpage for details.Synopsis:
 
 sigaction(sig, action, oldaction = 0)Returns undefon failure.
 
 
- 
siglongjmp
- 
siglongjmp()
 is C-specific: use die instead.
 
- 
sigpending
- 
Examine signals that are blocked and pending.  This uses 
POSIX::SigSet
objects for the sigsetargument.  Consult your system's 
sigpending
manpage for details.Synopsis:
 
 sigpending(sigset)Returns undefon failure.
 
 
- 
sigprocmask
- 
Change and/or examine calling process's signal mask.  This uses
POSIX::SigSet
 objects for the sigsetandoldsigsetarguments.
Consult your system's 
sigprocmask
 manpage for details.Synopsis:
 
 sigprocmask(how, sigset, oldsigset = 0)Returns undefon failure.
 
 
- 
sigsetjmp
- 
sigsetjmp()
 is C-specific: use eval {} instead.
 
- 
sigsuspend
- 
Install a signal mask and suspend process until signal arrives.  This uses
POSIX::SigSet
 objects for the signal_maskargument.  Consult your
system's 
sigsuspend
 manpage for details.Synopsis:
 
 sigsuspend(signal_mask)Returns undefon failure.
 
 
- 
sin
- 
This is identical to Perl's builtin 
sin()
 function.
 
- 
sinh
- 
This is identical to the C function 
sinh()
.
 
- 
sleep
- 
This is identical to Perl's builtin 
sleep()
 function.
 
- 
sprintf
- 
This is identical to Perl's builtin 
sprintf()
 function.
 
- 
sqrt
- 
This is identical to Perl's builtin 
sqrt()
 function.
 
- 
srand
- 
srand()
.
 
- 
sscanf
- 
sscanf()
 is C-specific--use regular expressions instead.
 
- 
stat
- 
This is identical to Perl's builtin 
stat()
 function.
 
- 
strcat
- 
strcat()
 is C-specific, use .= instead.
 
- 
strchr
- 
strchr()
 is C-specific, use index() instead.
 
- 
strcmp
- 
strcmp()
 is C-specific, use eq instead.
 
- 
strcoll
- 
This is identical to the C function 
strcoll()
.
 
- 
strcpy
- 
strcpy()
 is C-specific, use = instead.
 
- 
strcspn
- 
strcspn()
 is C-specific, use regular expressions instead.
 
- 
strerror
- 
Returns the error string for the specified errno.
 
- 
strftime
- 
Convert date and time information to string.  Returns the string.
Synopsis:
 
 strftime(fmt, sec, min, hour, mday, mon, year, wday = 0, yday = 0, isdst = 0)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.
 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
- 
strlen()
 is C-specific, use length instead.
 
- 
strncat
- 
strncat()
 is C-specific, use .= instead.
 
- 
strncmp
- 
strncmp()
 is C-specific, use eq instead.
 
- 
strncpy
- 
strncpy()
 is C-specific, use = instead.
 
- 
stroul
- 
stroul()
 is C-specific.
 
- 
strpbrk
- 
strpbrk()
 is C-specific.
 
- 
strrchr
- 
strrchr()
 is C-specific, use rindex() instead.
 
- 
strspn
- 
strspn()
 is C-specific.
 
- 
strstr
- 
This is identical to Perl's builtin index()function.
 
- 
strtod
- 
strtod()
 is C-specific.
 
- 
strtok
- 
strtok()
 is C-specific.
 
- 
strtol
- 
strtol()
 is C-specific.
 
- 
strxfrm
- 
String transformation.  Returns the transformed string.
 $dst = POSIX::strxfrm( $src );
 
- 
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 undefon failure.
 
 
- 
system
- 
This is identical to Perl's builtin 
system()
 function.
 
- 
tan
- 
This is identical to the C function 
tan()
.
 
- 
tanh
- 
This is identical to the C function 
tanh()
.
 
- 
tcdrain
- 
This is similar to the C function 
tcdrain()
.
Returns undefon failure.
 
 
- 
tcflow
- 
This is similar to the C function 
tcflow()
.
Returns undefon failure.
 
 
- 
tcflush
- 
This is similar to the C function 
tcflush()
.
Returns undefon failure.
 
 
- 
tcgetpgrp
- 
This is identical to the C function 
tcgetpgrp()
.
 
- 
tcsendbreak
- 
This is similar to the C function 
tcsendbreak()
.
Returns undefon failure.
 
 
- 
tcsetpgrp
- 
This is similar to the C function 
tcsetpgrp()
.
Returns undefon failure.
 
 
- 
time
- 
This is identical to Perl's builtin 
time()
 function.
 
- 
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
- 
Use method 
FileHandle::
new_tmpfile()
 instead.
 
- 
tmpnam
- 
Returns a name for a temporary file.
 $tmpfile = POSIX::tmpnam();
 
- 
tolower
- 
This is identical to Perl's builtin lc()function.
 
- 
toupper
- 
This is identical to Perl's builtin uc()function.
 
- 
ttyname
- 
This is identical to the C function 
ttyname()
.
 
- 
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()
.
 
- 
umask
- 
This is identical to Perl's builtin 
umask()
 function.
 
- 
uname
- 
Get name of current operating system.
 ($sysname, $nodename, $release, $version, $machine ) = POSIX::uname();
 
- 
ungetc
- 
Use method 
FileHandle::
ungetc()
 instead.
 
- 
unlink
- 
This is identical to Perl's builtin 
unlink()
 function.
 
- 
utime
- 
This is identical to Perl's builtin 
utime()
 function.
 
- 
vfprintf
- 
vfprintf()
 is C-specific.
 
- 
vprintf
- 
vprintf()
 is C-specific.
 
- 
vsprintf
- 
vsprintf()
 is C-specific.
 
- 
wait
- 
This is identical to Perl's builtin 
wait()
 function.
 
- 
waitpid
- 
Wait for a child process to change state.  This is identical to Perl's
builtin 
waitpid()
 function.
 $pid = POSIX::waitpid( -1, &POSIX::WNOHANG );
        print "status = ", ($? / 256), "\n";
 
- 
wcstombs
- 
This is identical to the C function 
wcstombs()
.
 
- 
wctomb
- 
This is identical to the C function 
wctomb()
.
 
- 
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( $b, $buf, 5 );Returns undefon failure.