posix(3)

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 %d0, 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. Things
which are "#defines" in C, like EINTR or O_NDELAY, are
automatically exported into your namespace. All functions
are only exported if you ask for them explicitly. Most
likely people will prefer to use the fully-qualified func
tion names.

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 fea
tures. 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 miscel
laneous objects. The remaining sections list various con
stants and macros in an organization which roughly follows
IEEE Std 1003.1b-1993.

NOTE

The POSIX module is probably the most complex Perl module
supplied with the standard distribution. It incorporates
autoloading, namespace games, and dynamic loading of code
that's in Perl, C, or both. It's a great source of wis
dom.

CAVEATS

A few functions are not implemented because they are C
specific. If you attempt to call these, they will print a
message telling you that they aren't implemented, and sug
gest 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 compli
ance, 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 val
ues 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.

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 han
dler does not return normally (it e.g. does a
"longjmp").

abs This is identical to Perl's builtin "abs()" func

tion, returning the absolute value of its numeri
cal argument.

access Determines the accessibility of a file.

if( POSIX::access( "/", &POSIX::R_OK ) ){

print "have read permission0;

}

Returns "undef" on failure. Note: do not use
"access()" for security purposes. Between the
"access()" call and the operation you are prepar
ing 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 argu
ment. 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 200000"

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. The $wday,
$yday, and $isdst default to zero (and the first
two are usually ignored anyway).

asin This is identical to the C function "asin()",

returning the arcus sine of its numerical argu
ment. 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 argu
ment. See also Math::Trig.

atan2 This is identical to Perl's builtin "atan2()"

function, returning the arcus tangent defined by
its two numerical arguments, the y coordinate and
the x coordinate. See also Math::Trig.

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

perlsub.

atof atof() is C-specific. Perl converts strings to

numbers transparently. If you need to force a
scalar to a number, add a zero to it.

atoi atoi() is C-specific. Perl converts strings to

numbers transparently. If you need to force a
scalar to a number, add a zero to it. If you need
to have just the integer part, see "int" in perl
func.

atol atol() is C-specific. Perl converts strings to

numbers transparently. If you need to force a
scalar to a number, add a zero to it. If you need
to have just the integer part, see "int" in perl
func.

bsearch bsearch() not supplied. For doing binary search

on wordlists, see Search::Dict.

calloc calloc() is C-specific. Perl does memory manage

ment transparently.

ceil This is identical to the C function "ceil()",

returning the smallest integer value greater than
or equal to the given numerical argument.

chdir This is identical to Perl's builtin "chdir()"

function, allowing one to change the working
(default) directory, see "chdir" in perlfunc.

chmod This is identical to Perl's builtin "chmod()"

function, allowing one to change file and direc
tory permissions, see "chmod" in perlfunc.

chown This is identical to Perl's builtin "chown()"

function, allowing one to change file and direc
tory owners and groups, see "chown" in perlfunc.

clearerr

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

clock This is identical to the C function "clock()",

returning the amount of spent processor time in
microseconds.

close Close the file. This uses file descriptors such

as those obtained by calling "POSIX::open".

$fd = POSIX::open( "foo", &POSIX::O_RDONLY

);
POSIX::close( $fd );

Returns "undef" on failure.

See also "close" in perlfunc.

closedir

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

cos This is identical to Perl's builtin "cos()" func

tion, for returning the cosine of its numerical
argument, see "cos" in perlfunc. See also
Math::Trig.

cosh This is identical to the C function "cosh()", for

returning the hyperbolic cosine of its numeric
argument. See also Math::Trig.

creat Create a new file. This returns a file descriptor

like the ones returned by "POSIX::open". Use
"POSIX::close" to close the file.

$fd = POSIX::creat( "foo", 0611 );
POSIX::close( $fd );

See also "sysopen" in perlfunc and its "O_CREAT"
flag.

ctermid Generates the path name for the controlling termi

nal.

$path = POSIX::ctermid();

ctime This is identical to the C function "ctime()" and

equivalent to "asctime(localtime(...))", see "asc
time" and "localtime".

cuserid Get the login name of the owner of the current

process.

$name = POSIX::cuserid();

difftime

This is identical to the C function "difftime()",
for returning the time difference (in seconds)
between two times (as returned by "time()"), see
"time".

div div() is C-specific, use "int" in perlfunc on the

usual "/" division and the modulus "%".

dup This is similar to the C function "dup()", for

duplicating a file descriptor.

This uses file descriptors such as those obtained
by calling "POSIX::open".

Returns "undef" on failure.

dup2 This is similar to the C function "dup2()", for

duplicating a file descriptor to an another known
file descriptor.

This uses file descriptors such as those obtained
by calling "POSIX::open".

Returns "undef" on failure.

errno Returns the value of errno.

$errno = POSIX::errno();

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

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

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

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

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

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

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

exit This is identical to Perl's builtin "exit()" func

tion for exiting the program, see "exit" in perl
func.

exp This is identical to Perl's builtin "exp()" func

tion for returning the exponent (e-based) of the
numerical argument, see "exp" in perlfunc.

fabs This is identical to Perl's builtin "abs()" func

tion for returning the absolute value of the
numerical argument, see "abs" in perlfunc.

fclose Use method "IO::Handle::close()" instead, or see

"close" in perlfunc.

fcntl This is identical to Perl's builtin "fcntl()"

function, see "fcntl" in perlfunc.

fdopen Use method "IO::Handle::new_from_fd()" instead, or

see "open" in perlfunc.

feof Use method "IO::Handle::eof()" instead, or see

"eof" in perlfunc.

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

fflush Use method "IO::Handle::flush()" instead. See

also "$OUTPUT_AUTOFLUSH" in perlvar.

fgetc Use method "IO::Handle::getc()" instead, or see

"read" in perlfunc.

fgetpos Use method "IO::Seekable::getpos()" instead, or

see "seek" in L.

fgets Use method "IO::Handle::gets()" instead. Similar

to <>, also known as "readline" in perlfunc.

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

"fileno" in perlfunc.

floor This is identical to the C function "floor()",

returning the largest integer value less than or
equal to the numerical argument.

fmod This is identical to the C function "fmod()".

$r = fmod($x, $y);

It returns the remainder "$r = $x - $n*$y", where
"$n = trunc($x/$y)". The $r has the same sign as
$x and magnitude (absolute value) less than the
magnitude of $y.

fopen Use method "IO::File::open()" instead, or see

"open" in perlfunc.

fork This is identical to Perl's builtin "fork()" func

tion for duplicating the current process, see
"fork" in perlfunc and perlfork if you are in Win
dows.

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 "undef" on failure.

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

instead.

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

instead.

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

instead.

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

instead.

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

transparently.

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

instead.

frexp Return the mantissa and exponent of a floating

point number.

($mantissa, $exponent) = POSIX::frexp(

1.234e56 );

fscanf fscanf() is C-specific, use <> and regular expres

sions instead.

fseek Use method "IO::Seekable::seek()" instead, or see

"seek" in perlfunc.

fsetpos Use method "IO::Seekable::setpos()" instead, or

seek "seek" in perlfunc.

fstat Get file status. This uses file descriptors such

as those obtained by calling "POSIX::open". The
data returned is identical to the data from Perl's
builtin "stat" function.

$fd = POSIX::open( "foo", &POSIX::O_RDONLY

);
@stats = POSIX::fstat( $fd );

ftell Use method "IO::Seekable::tell()" instead, or see

"tell" in perlfunc.

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

instead.

getc This is identical to Perl's builtin "getc()" func

tion, 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 enironment

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 per
lvar.

getgid Returns the user's real group identifier. Similar

to Perl's builtin variable $), see "$GID" in perl
var.

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 perl
func.

getpgrp This is identical to Perl's builtin "getpgrp()"

function for returning the prcess 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 iden
tifiers, see "getpwuid" in perlfunc.

gets Returns one line from "STDIN", similar to <>, also

known as the "readline()" function, see "readline"
in perlfunc.

NOTE: if you have C programs that still use
"gets()", be very afraid. The "gets()" function
is a source of endless grief because it has no
buffer overrun checks. It should never be used.
The "fgets()" function should be preferred
instead.

getuid Returns the user's identifier. Identical to

Perl's builtin $< variable, see "$UID" in perlvar.

gmtime This is identical to Perl's builtin "gmtime()"

function for converting seconds since the epoch to
a date in Greenwich Mean Time, see "gmtime" in
perlfunc.

isalnum This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:alnum:]]/" construct instead, or possibly
the "/288

isalpha This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:alpha:]]/" construct instead.

isatty Returns a boolean indicating whether the specified

filehandle is connected to a tty. Similar to the
"-t" operator, see "-X" in perlfunc.

iscntrl This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:cntrl:]]/" construct instead.

isdigit This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:digit:]]/" construct instead, or the
"//" construct.

isgraph This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:graph:]]/" construct instead.

islower This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:lower:]]/" construct instead. Do not use
"/[a-z]/".

isprint This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:print:]]/" construct instead.

ispunct This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:punct:]]/" construct instead.

isspace This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:space:]]/" construct instead, or the
"/" construct. (Note that "/" and
"/[[:space:]]/" are slightly different in that
"/[[:space:]]/" can normally match a vertical tab,
while "/" does not.)

isupper This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:upper:]]/" construct instead. Do not use
"/[A-Z]/".

isxdigit

This is identical to the C function, except that
it can apply to a single character or to a whole
string. Consider using regular expressions and
the "/[[:xdigit:]]/" construct instead, or simply
"/[0-9a-f]/i".

kill This is identical to Perl's builtin "kill()" func

tion for sending signals to processes (often to
terminate them), see "kill" in perlfunc.

labs (For returning absolute values of long integers.)

labs() is C-specific, see "abs" in perlfunc
instead.

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 (For computing dividends of long integers.)

ldiv() is C-specific, use "/" and "int()" instead.

link This is identical to Perl's builtin "link()" func

tion for creating hard links into files, see
"link" in perlfunc.

localeconv

Get numeric formatting information. Returns a
reference to a hash containing the current locale
formatting values.

Here is how to query the database for the de
(Deutsch or German) locale.

$loc = POSIX::setlocale( &POSIX::LC_ALL,

"de" );
print "Locale = $loc0;
$lconv = POSIX::localeconv();
print "decimal_point = ", $lconv->{dec

imal_point}, "0;
print "thousands_sep = ",

$lconv->{thousands_sep}, "0;
print "grouping = ", $lconv->{grouping},

"0;
print "int_curr_symbol = ",

$lconv->{int_curr_symbol}, "0;
print "currency_symbol = ", $lconv->{cur

rency_symbol}, "0;
print "mon_decimal_point = ",

$lconv->{mon_decimal_point}, "0;
print "mon_thousands_sep = ",

$lconv->{mon_thousands_sep}, "0;
print "mon_grouping = ",

$lconv->{mon_grouping}, "0;
print "positive_sign = ", $lconv->{pos

itive_sign}, "0;
print "negative_sign = ", $lconv->{neg

ative_sign}, "0;
print "int_frac_digits = ",

$lconv->{int_frac_digits}, "0;
print "frac_digits = ",

$lconv->{frac_digits}, "0;
print "p_cs_precedes = ",

$lconv->{p_cs_precedes}, "0;
print "p_sep_by_space = ",

$lconv->{p_sep_by_space}, "0;
print "n_cs_precedes = ",

$lconv->{n_cs_precedes}, "0;
print "n_sep_by_space = ",

$lconv->{n_sep_by_space}, "0;
print "p_sign_posn = ",

$lconv->{p_sign_posn}, "0;
print "n_sign_posn = ",

$lconv->{n_sign_posn}, "0;

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()" func

tion, 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 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.

malloc malloc() is C-specific. Perl does memory manage

ment transparently.

mblen This is identical to the C function "mblen()".

Perl does not have any support for the wide and
multibyte characters of the C standards, so this
might be a rather useless function.

mbstowcs

This is identical to the C function "mbstowcs()".
Perl does not have any support for the wide and
multibyte characters of the C standards, so this
might be a rather useless function.

mbtowc This is identical to the C function "mbtowc()".

Perl does not have any support for the wide and
multibyte characters of the C standards, so this
might be a rather useless function.

memchr memchr() is C-specific, see "index" in perlfunc

instead.

memcmp memcmp() is C-specific, use "eq" instead, see per

lop.

memcpy memcpy() is C-specific, use "=", see perlop, or

see "substr" in perlfunc.

memmove memmove() is C-specific, use "=", see perlop, or

see "substr" in perlfunc.

memset memset() is C-specific, use "x" instead, see per

lop.

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.

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. Con
sult 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 );

nice This is similar to the C function "nice()", for

changing the scheduling preference of the current
process. Positive arguments mean more polite
process, negative values more needy process. Nor
mal user processes can only be more polite.

Returns "undef" on failure.

offsetof

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( "/tmp" );
@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 "/tmp".

$path_max = POSIX::pathconf( "/tmp",

&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".

($fd0, $fd1) = POSIX::pipe();
POSIX::write( $fd0, "hello", 5 );
POSIX::read( $fd1, $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 STD

OUT. See also "printf" in perlfunc.

putc putc() is C-specific, see "print" in perlfunc

instead.

putchar putchar() is C-specific, see "print" in perlfunc

instead.

puts puts() is C-specific, see "print" in perlfunc

instead.

qsort 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 "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 "read
dir" in perlfunc.

realloc realloc() is C-specific. Perl does memory manage

ment transparently.

remove This is identical to Perl's builtin "unlink()"

function for removing files, see "unlink" in perl
func.

rename This is identical to Perl's builtin "rename()"

function for renaming files, see "rename" in perl
func.

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.

rmdir This is identical to Perl's builtin "rmdir()"

function for removing (empty) directories, see
"rmdir" in perlfunc.

scanf scanf() is C-specific, use <> and regular expres

sions 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 $) vari
able, see "$GID" in perlvar, except that the lat
ter will change only the real user identifier, and
that the setgid() uses only a single numeric argu ment, as opposed to a space-separated list of num
bers.

setjmp "setjmp()" is C-specific: use "eval {}" instead,

see "eval" in perlfunc.

setlocale

Modifies and queries program's locale. The fol
lowing 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 cat
egory. (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 systems set
locale(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 avail
ability of locales depends on your operating sys
tem. Please consult perllocale for how to find out
which locales are available in your system.

$loc = setlocale( LC_ALL,

"es_AR.ISO8859-1" );

setpgid This is similar to the C function "setpgid()" for

setting the process group identifier of the cur
rent process.

Returns "undef" on failure.

setsid This is identical to the C function "setsid()" for

setting the session identifier of the current pro
cess.

setuid Sets the real user identifier and the effective

user identifier for this process. Similar to
assigning a value to the Perl's builtin $< vari
able, see "$UID" in perlvar, except that the lat
ter will change only the real user identifier.

sigaction

Detailed signal management. This uses
"POSIX::SigAction" objects for the "action" and
"oldaction" arguments. Consult your system's
"sigaction" manpage for details.

Synopsis:

sigaction(sig, action, oldaction = 0)

Returns "undef" on failure.

siglongjmp

siglongjmp() is C-specific: use "die" in perlfunc instead.

sigpending

Examine signals that are blocked and pending.
This uses "POSIX::SigSet" objects for the "sigset"
argument. Consult your system's "sigpending" man
page 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.

sigsetjmp

"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 sys
tem's "sigsuspend" manpage for details.

Synopsis:

sigsuspend(signal_mask)

Returns "undef" on failure.

sin This is identical to Perl's builtin "sin()" func

tion for returning the sine of the numerical argu
ment, 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 sec
onds, see "sleep" in perlfunc. There is one sig
nifanct difference, however: "POSIX::sleep()"
returns the number of unslept seconds, while the "CORE::sleep()" returns the number of slept sec
onds.

sprintf This is similar to Perl's builtin "sprintf()"

function for returning a string that has the argu
ments formatted as requested, see "sprintf" in
perlfunc.

sqrt This is identical to Perl's builtin "sqrt()" func

tion. for returning the square root of the numer
ical argument, see "sqrt" in perlfunc.

srand Give a seed the pseudorandom number generator, see

"srand" in perlfunc.

sscanf sscanf() is C-specific, use regular expressions

instead, see perlre.

stat This is identical to Perl's builtin "stat()" func

tion for retutning information about files and
directories.

strcat strcat() is C-specific, use ".=" instead, see per

lop.

strchr strchr() is C-specific, see "index" in perlfunc

instead.

strcmp 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 perllo
cale.

strcpy strcpy() is C-specific, use "=" instead, see per

lop.

strcspn 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 the $!, see
"$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. Con
sult 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. These
are "aAbBcdHIjmMpSUwWxXyYZ%". The given arguments
are made consistent as though by calling
"mktime()" before calling your system's "strf
time()" 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 "$str0;

strlen strlen() is C-specific, use "length()" instead,

see "length" in perlfunc.

strncat strncat() is C-specific, use ".=" instead, see

perlop.

strncmp strncmp() is C-specific, use "eq" instead, see

perlop.

strncpy strncpy() is C-specific, use "=" instead, see per

lop.

strpbrk strpbrk() is C-specific, use regular expressions

instead, see perlre.

strrchr strrchr() is C-specific, see "rindex" in perlfunc

instead.

strspn 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-com
pliant systems set $! ($ERRNO) to indicate a
translation error, so clear $! before calling str
tod. However, non-POSIX systems may not check for
overflow, and therefore will never set $!.

strtod should respect any POSIX setlocale() set tings.

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" . $! ? ": $!0

: "0;

}

When called in a scalar context strtod returns the
parsed number.

strtok 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-com
pliant systems set $! ($ERRNO) to indicate a
translation error, so clear $! before calling str
tol. However, non-POSIX systems may not check for
overflow, and therefore will never set $!.

strtol should respect any POSIX setlocale() set tings.

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 str
tol will use the string itself to determine the
base: a leading "0x" or "0X" means hexadecimal; a
leading "0" means octal; any other leading charac
ters 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" . $! ? ": $!0

: "0;

}

When called in a scalar context strtol returns the
parsed number.

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 transpar
ently, 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 argumeny 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 termi
nal.

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 termi
nal.

Returns "undef" on failure.

time This is identical to Perl's builtin "time()" func

tion 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 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. Consider using the "lc()" function, see
"lc" in perlfunc, or the equivalent "perator
inside doublequotish strings.

toupper This is identical to the C function, except that

it can apply to a single character or to a whole
string. Consider using the "uc()" function, see
"uc" in perlfunc, or the equivalent "U" operator
inside doublequotish strings.

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 environ
ment variable "TZ", to be used by "ctime()",
"localtime()", "mktime()", and "strftime()" func
tions.

umask This is identical to Perl's builtin "umask()"

function for setting (and querying) the file cre
ation 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 Use method "IO::Handle::ungetc()" instead.

unlink This is identical to Perl's builtin "unlink()"

function for removing files, see "unlink" in perl
func.

utime This is identical to Perl's builtin "utime()"

function for changing the time stamps of files and
directories, see "utime" in perlfunc.

vfprintf

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

vprintf vprintf() is C-specific, see "printf" in perlfunc

instead.

vsprintf

vsprintf() is C-specific, see "sprintf" in perl func instead.

wait This is identical to Perl's builtin "wait()" func

tion, 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), "0;

wcstombs

This is identical to the C function "wcstombs()".
Perl does not have any support for the wide and
multibyte characters of the C standards, so this
might be a rather useless function.

wctomb This is identical to the C function "wctomb()".

Perl does not have any support for the wide and
multibyte characters of the C standards, so this
might be a rather useless function.

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 "undef" on failure.

See also "syswrite" in perlfunc.

CLASSES

POSIX::SigAction

new Creates a new "POSIX::SigAction" object which cor

responds to the C "struct sigaction". This object
will be destroyed automatically when it is no
longer needed. The first parameter is the fullyqualified name of a sub which is a signal-handler.
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(

'main::handler', $sigset, &POSIX::SA_NOCLDSTOP );

This "POSIX::SigAction" object should be used with
the "POSIX::sigaction()" function.

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::SI

GUSR1 );

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 sig

nals.

$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 SIGUSR10;

}

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()

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_VDIS
ABLE _POSIX_VERSION

SYSTEM CONFIGURATION

Constants

_SC_ARG_MAX _SC_CHILD_MAX _SC_CLK_TCK _SC_JOB_CON
TROL _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 EBUSY ECHILD ECONNABORTED
ECONNREFUSED ECONNRESET EDEADLK EDESTADDRREQ EDOM
EDQUOT EEXIST EFAULT EFBIG EHOSTDOWN EHOSTUNREACH
EINPROGRESS EINTR EINVAL EIO EISCONN EISDIR ELOOP
EMFILE EMLINK EMSGSIZE ENAMETOOLONG ENETDOWN ENE
TRESET ENETUNREACH ENFILE ENOBUFS ENODEV ENOENT
ENOEXEC ENOLCK ENOMEM ENOPROTOOPT ENOSPC ENOSYS
ENOTBLK ENOTCONN ENOTDIR ENOTEMPTY ENOTSOCK ENOTTY
ENXIO EOPNOTSUPP EPERM EPFNOSUPPORT EPIPE EPROCLIM
EPROTONOSUPPORT EPROTOTYPE ERANGE EREMOTE ERESTART
EROFS ESHUTDOWN ESOCKTNOSUPPORT ESPIPE ESRCH
ESTALE 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

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

MATH

Constants

HUGE_VAL

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_tmp
name TMP_MAX

TIME

Constants

CLK_TCK CLOCKS_PER_SEC

UNISTD

Constants

R_OK SEEK_CUR SEEK_END SEEK_SET STDIN_FILENO STD
OUT_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 immedi
ately.

WUNTRACED Catch stopped child processes.

Macros WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIF

STOPPED WSTOPSIG

WIFEXITED WIFEXITED($?) returns true if the

child process exited normally
("exit()" or by falling off the
end of "main()")

WEXITSTATUS WEXITSTATUS($?) returns the normal

exit status of the child process
(only meaningful if WIFEXITED($?)
is true)

WIFSIGNALED WIFSIGNALED($?) returns true if

the child process terminated
because of a signal

WTERMSIG WTERMSIG($?) returns the signal

the child process terminated for
(only meaningful if WIFSIG
NALED($?) is true)

WIFSTOPPED WIFSTOPPED($?) returns true if the

child process is currently stopped
(can happen only if you specified
the WUNTRACED flag to waitpid())

WSTOPSIG WSTOPSIG($?) returns the signal

the child process was stopped for
(only meaningful if WIFSTOPPED($?)
is true)

perl v5.8.0 2002-06-01 POSIX(3)