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 %d\n", EINTR;

    $sess_id = POSIX::setsid();

    $fd = POSIX::open($path, O_CREAT|O_EXCL|O_WRONLY, 0644);
        # note: that's a filedescriptor, *NOT* a filehandle

DESCRIPTION
The POSIX module permits you to access all (or nearly all) the standard POSIX 1003.1 identifiers. Many of these identifiers have been given Perl-ish interfaces. 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 function 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 features. Consult perlfunc for functions which are noted as being identical to Perl's builtin functions.

The first section describes POSIX functions from the 1003.1 specification. The second section describes some classes for signal objects, TTY objects, and other miscellaneous objects. The remaining sections list various constants and macros in an organization which roughly follows IEEE Std 1003.1b-1993.

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 wisdom.

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 suggest using the Perl equivalent should one exist. For example, trying to access the setjmp() call will elicit the message "setjmp() is C-specific: use eval {} instead".

Furthermore, some evil vendors will claim 1003.1 compliance, but in fact are not so: they will not pass the PCTS (POSIX Compliance Test Suites). For example, one vendor may not define EDEADLK, or the semantics of the errno values set by open(2) might not be quite right. Perl does not attempt to verify POSIX compliance. That means you can currently successfully say "use POSIX", and then later in your program you find that your vendor has been lax and there's no usable ICANON macro after all. This could be construed to be a bug.

FUNCTIONS

_exit
    This is identical to the C function "_exit()". It exits the program immediately which means among other things buffered I/O is not flushed.

abort
    This is identical to the C function "abort()". It terminates the process with a "SIGABRT" signal unless caught by a signal handler or if the handler does not return normally (it e.g. does a "longjmp").

abs This is identical to Perl's builtin "abs()" function, returning the absolute value of its numerical argument.

access
    Determines the accessibility of a file.

            if( POSIX::access( "/", &POSIX::R_OK ) ){
                    print "have read permission\n";
            }

    Returns "undef" on failure. Note: do not use "access()" for security purposes. Between the "access()" call and the operation you are preparing for the permissions might change: a classic race condition.

acos
    This is identical to the C function "acos()", returning the arcus cosine of its numerical argument. See also Math::Trig.

alarm
    This is identical to Perl's builtin "alarm()" function, either for arming or disarming the "SIGARLM" timer.

asctime
    This is identical to the C function "asctime()". It returns a string of the form

            "Fri Jun  2 18:22:13 2000\n\0"

    and it is called thusly

            $asctime = asctime($sec, $min, $hour, $mday, $mon, $year,
                               $wday, $yday, $isdst);

    The $mon is zero-based: January equals 0. The $year is 1900-based: 2001 equals 101. 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 argument. See also Math::Trig.

assert
    Unimplemented, but you can use "die" in perlfunc and the Carp module to achieve similar things.

atan
    This is identical to the C function "atan()", returning the arcus tangent of its numerical argument. See also Math::Trig.

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 perlfunc.

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 perlfunc.

bsearch
    bsearch() not supplied. For doing binary search on wordlists, see Search::Dict.

calloc
    calloc() is C-specific. Perl does memory management 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 directory permissions, see "chmod" in perlfunc.

chown
    This is identical to Perl's builtin "chown()" function, allowing one to change file and directory owners and groups, see "chown" in perlfunc.

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

clock
    This is identical to the C function "clock()", returning the amount of spent processor time in microseconds.

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

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

    Returns "undef" on failure.

    See also "close" in perlfunc.

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

cos This is identical to Perl's builtin "cos()" function, for returning the cosine of its numerical argument, see "cos" in perlfunc. See also Math::Trig.

cosh
    This is identical to the C function "cosh()", for returning the hyperbolic cosine of its numeric argument. See also Math::Trig.

creat
    Create a new file. This returns a file descriptor like the ones returned by "POSIX::open". Use "POSIX::close" to close the file.

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

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

ctermid
    Generates the path name for the controlling terminal.

            $path = POSIX::ctermid();

ctime
    This is identical to the C function "ctime()" and equivalent to "asctime(localtime(...))", see "asctime" and "localtime".

cuserid
    Get the login name of the owner of the current process.

            $name = POSIX::cuserid();

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

div 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()" function for exiting the program, see "exit" in perlfunc.

exp This is identical to Perl's builtin "exp()" function for returning the exponent (e-based) of the numerical argument, see "exp" in perlfunc.

fabs
    This is identical to Perl's builtin "abs()" function 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()" function for duplicating the current process, see "fork" in perlfunc and perlfork if you are in Windows.

fpathconf
    Retrieves the value of a configurable limit on a file or directory. This uses file descriptors such as those obtained by calling "POSIX::open".

    The following will determine the maximum length of the longest allowable pathname on the filesystem which holds "/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 expressions 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()" function, see "getc" in perlfunc.

getchar
    Returns one character from STDIN. Identical to Perl's "getc()", see "getc" in perlfunc.

getcwd
    Returns the name of the current working directory. See also Cwd.

getegid
    Returns the effective group identifier. Similar to Perl' s builtin variable $(, see "$EGID" in perlvar.

getenv
    Returns the value of the specified 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 perlvar.

getgid
    Returns the user's real group identifier. Similar to Perl's builtin variable $), see "$GID" in perlvar.

getgrgid
    This is identical to Perl's builtin "getgrgid()" function for returning group entries by group identifiers, see "getgrgid" in perlfunc.

getgrnam
    This is identical to Perl's builtin "getgrnam()" function for returning group entries by group names, see "getgrnam" in perlfunc.

getgroups
    Returns the ids of the user's supplementary groups. Similar to Perl's builtin variable $), see "$GID" in perlvar.

getlogin
    This is identical to Perl's builtin "getlogin()" function for returning the user name associated with the current session, see "getlogin" in perlfunc.

getpgrp
    This is identical to Perl's builtin "getpgrp()" function for returning the 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 identifiers, see "getpwuid" in perlfunc.

gets
    Returns one line from "STDIN", similar to <>, also known as the "readline()" function, see "readline" in perlfunc.

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

getuid
    Returns the user's identifier. Identical to Perl's builtin $< variable, see "$UID" in perlvar.

gmtime
    This is identical to Perl's builtin "gmtime()" function for converting seconds since the epoch to a date in Greenwich Mean Time, see "gmtime" in perlfunc.

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 "/\w/" construct.

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 "/\d/" 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 "/\s/" construct. (Note that "/\s/" and "/[[:space:]]/" are slightly different in that "/[[:space:]]/" can normally match a vertical tab, while "/\s/" 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()" function 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()" function for creating hard links into files, see "link" in perlfunc.

localeconv
    Get numeric formatting information. Returns a reference to a hash containing the current 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 = $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 for converting seconds since the epoch to a date see "localtime" in perlfunc.

log This is identical to Perl's builtin "log()" function, returning the natural (e-based) logarithm of the numerical argument, see "log" in perlfunc.

log10
    This is identical to the C function "log10()", returning the 10-base logarithm of the numerical argument. You can also use

        sub log10 { log($_[0]) / log(10) }

    or

        sub log10 { log($_[0]) / 2.30258509299405 }

    or

        sub log10 { log($_[0]) * 0.434294481903252 }

longjmp
    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 management 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 perlop.

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 perlop.

mkdir
    This is identical to Perl's builtin "mkdir()" function for creating directories, see "mkdir" in perlfunc.

mkfifo
    This is similar to the C function "mkfifo()" for creating FIFO special files.

            if (mkfifo($path, $mode)) { ....

    Returns "undef" on failure. The $mode is similar to the mode of "mkdir()", see "mkdir" in perlfunc.

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 "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. Normal 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 STDOUT. 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 "readdir" in perlfunc.

realloc
    realloc() is C-specific. Perl does memory management transparently.

remove
    This is identical to Perl's builtin "unlink()" function for removing files, see "unlink" in perlfunc.

rename
    This is identical to Perl's builtin "rename()" function for renaming files, see "rename" in perlfunc.

rewind
    Seeks to the beginning of the file.

rewinddir
    This is identical to Perl's builtin "rewinddir()" function for rewinding directory entry streams, see "rewinddir" in perlfunc.

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 expressions instead, see perlre.

setgid
    Sets the real group identifier and the effective group identifier for this process. Similar to assigning a value to the Perl's builtin $) variable, see "$GID" in perlvar, except that the latter will change only the real user identifier, and that the setgid() uses only a single numeric argument, as opposed to a space-separated list of numbers.

setjmp
    "setjmp()" is C-specific: use "eval {}" instead, see "eval" in perlfunc.

setlocale
    Modifies and queries program's locale. The following examples assume

            use POSIX qw(setlocale LC_ALL LC_CTYPE);

    has been issued.

    The following will set the traditional UNIX system locale behavior (the second argument "C").

            $loc = setlocale( LC_ALL, "C" );

    The following will query the current LC_CTYPE category. (No second argument means 'query'.)

            $loc = setlocale( LC_CTYPE );

    The following will set the LC_CTYPE behaviour according to the locale environment variables (the second argument ""). Please see your systems setlocale(3) documentation for the locale environment variables' meaning or consult perllocale.

            $loc = setlocale( LC_CTYPE, "" );

    The following will set the LC_COLLATE behaviour to Argentinian Spanish. NOTE: The naming and availability of locales depends on your operating system. Please consult perllocale for how to find out which locales are available in your system.

            $loc = setlocale( LC_ALL, "es_AR.ISO8859-1" );

setpgid
    This is similar to the C function "setpgid()" for setting the process group identifier of the current process.

    Returns "undef" on failure.

setsid
    This is identical to the C function "setsid()" for setting the session identifier of the current process.

setuid
    Sets the real user identifier and the effective user identifier for this process. Similar to assigning a value to the Perl's builtin $< variable, see "$UID" in perlvar, except that the latter will change only the real user identifier.

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

    Synopsis:

            sigpending(sigset)

    Returns "undef" on failure.

sigprocmask
    Change and/or examine calling process's signal mask. This uses "POSIX::SigSet" objects for the "sigset" and "oldsigset" arguments. Consult your system's "sigprocmask" manpage for details.

    Synopsis:

            sigprocmask(how, sigset, oldsigset = 0)

    Returns "undef" on failure.

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 system's "sigsuspend" manpage for details.

    Synopsis:

            sigsuspend(signal_mask)

    Returns "undef" on failure.

sin This is identical to Perl's builtin "sin()" function for returning the sine of the numerical argument, see "sin" in perlfunc. See also Math::Trig.

sinh
    This is identical to the C function "sinh()" for returning the hyperbolic sine of the numerical argument. See also Math::Trig.

sleep
    This is functionally identical to Perl's builtin "sleep()" function for suspending the execution of the current for process for certain number of seconds, see "sleep" in perlfunc. There is one signifanct difference, however: "POSIX::sleep()" returns the number of unslept seconds, while the "CORE::sleep()" returns the number of slept seconds.

sprintf
    This is similar to Perl's builtin "sprintf()" function for returning a string that has the arguments formatted as requested, see "sprintf" in perlfunc.

sqrt
    This is identical to Perl's builtin "sqrt()" function. for returning the square root of the numerical argument, see "sqrt" in perlfunc.

srand
    Give a seed the pseudorandom number generator, see "srand" in perlfunc.

sscanf
    sscanf() is C-specific, use regular expressions instead, see perlre.

stat
    This is identical to Perl's builtin "stat()" function for retutning information about files and directories.

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

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 perllocale.

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

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. Consult your system's "strftime()" manpage for details about these and the other arguments. If you want your code to be portable, your format ("fmt") argument should use only the conversion specifiers defined by the ANSI C standard. These are "aAbBcdHIjmMpSUwWxXyYZ%". The given arguments are made consistent as though by calling "mktime()" before calling your system's "strftime()" function, except that the "isdst" value is not affected.

    The string for Tuesday, December 12, 1995.

            $str = POSIX::strftime( "%A, %B %d, %Y", 0, 0, 0, 12, 11, 95, 2 );
            print "$str\n";

strlen
    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 perlop.

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

    strtod should respect any POSIX setlocale() settings.

    To parse a string $str as a floating point number use

        $! = 0;
        ($num, $n_unparsed) = POSIX::strtod($str);

    The second returned item and $! can be used to check for valid input:

        if (($str eq '') || ($n_unparsed != 0) || !$!) {
            die "Non-numeric input $str" . $! ? ": $!\n" : "\n";
        }

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

strtok
    strtok() is C-specific, use regular expressions instead, see perlre, or "split" in perlfunc.

strtol
    String to (long) integer translation. Returns the parsed number and the number of characters in the unparsed portion of the string. Truly POSIX-compliant systems set $! ($ERRNO) to indicate a translation error, so clear $! before calling strtol. However, non-POSIX systems may not check for overflow, and therefore will never set $!.

    strtol should respect any POSIX setlocale() settings.

    To parse a string $str as a number in some base $base use

        $! = 0;
        ($num, $n_unparsed) = POSIX::strtol($str, $base);

    The base should be zero or between 2 and 36, inclusive. When the base is zero or omitted strtol will use the string itself to determine the base: a leading "0x" or "0X" means hexadecimal; a leading "0" means octal; any other leading characters mean decimal. Thus, "1234" is parsed as a decimal number, "01234" as an octal number, and "0x1234" as a hexadecimal number.

    The second returned item and $! can be used to check for valid input:

        if (($str eq '') || ($n_unparsed != 0) || !$!) {
            die "Non-numeric input $str" . $! ? ": $!\n" : "\n";
        }

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

strtoul
    String to unsigned (long) integer translation. strtoul() is identical to strtol() except that strtoul() only parses unsigned integers. See "strtol" for details.

    Note: Some vendors supply strtod() and strtol() but not strtoul(). Other vendors that do supply strtoul() parse "-1" as a valid value.

strxfrm
    String transformation. Returns the transformed string.

            $dst = POSIX::strxfrm( $src );

    Used in conjunction with the "strcoll()" function, see "strcoll".

    Not really needed since Perl can do this transparently, see perllocale.

sysconf
    Retrieves values of system configurable variables.

    The following will get the machine's clock speed.

            $clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );

    Returns "undef" on failure.

system
    This is identical to Perl's builtin "system()" function, see "system" in perlfunc.

tan This is identical to the C function "tan()", returning the tangent of the numerical argument. See also Math::Trig.

tanh
    This is identical to the C function "tanh()", returning the hyperbolic tangent of the numerical argument. See also Math::Trig.

tcdrain
    This is similar to the C function "tcdrain()" for draining the output queue of its argument stream.

    Returns "undef" on failure.

tcflow
    This is similar to the C function "tcflow()" for controlling the flow of its argument stream.

    Returns "undef" on failure.

tcflush
    This is similar to the C function "tcflush()" for flushing the I/O buffers of its 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 terminal.

tcsendbreak
    This is similar to the C function "tcsendbreak()" for sending a break on its argument stream.

    Returns "undef" on failure.

tcsetpgrp
    This is similar to the C function "tcsetpgrp()" for setting the process group identifier of the foreground process group of the controlling terminal.

    Returns "undef" on failure.

time
    This is identical to Perl's builtin "time()" function for returning the number of seconds since the epoch (whatever it is for the system), see "time" in perlfunc.

times
    The times() function returns elapsed realtime since some point in the past (such as system startup), user and system times for this process, and user and system times used by child processes. All times are returned in clock ticks.

        ($realtime, $user, $system, $cuser, $csystem) = POSIX::times();

    Note: Perl's builtin "times()" function returns four values, measured in seconds.

tmpfile
    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 "\L" operator 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 environment variable "TZ", to be used by "ctime()", "localtime()", "mktime()", and "strftime()" functions.

umask
    This is identical to Perl's builtin "umask()" function for setting (and querying) the file creation permission mask, see "umask" in perlfunc.

uname
    Get name of current operating system.

            ($sysname, $nodename, $release, $version, $machine) = POSIX::uname();

    Note that the actual meanings of the various fields are not that well standardized, do not expect any great portability. The $sysname might be the name of the operating system, the $nodename might be the name of the host, the $release might be the (major) release number of the operating system, the $version might be the (minor) release number of the operating system, and the $machine might be a hardware identifier. Maybe.

ungetc
    Use method "IO::Handle::ungetc()" instead.

unlink
    This is identical to Perl's builtin "unlink()" function for removing files, see "unlink" in perlfunc.

utime
    This is identical to Perl's builtin "utime()" function for changing the time stamps of files and directories, see "utime" in perlfunc.

vfprintf
    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 perlfunc instead.

wait
    This is identical to Perl's builtin "wait()" function, see "wait" in perlfunc.

waitpid
    Wait for a child process to change state. This is identical to Perl's builtin "waitpid()" function, see "waitpid" in perlfunc.

            $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
            print "status = ", ($? / 256), "\n";

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

new Creates a new "POSIX::SigAction" object which corresponds to the C "struct sigaction". This object will be destroyed automatically when it is no longer needed. The first parameter is the fully-qualified 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.

new Create a new SigSet object. This object will be destroyed automatically when it is no longer needed. Arguments may be supplied to initialize the set.

    Create an empty set.

            $sigset = POSIX::SigSet->new;

    Create a set with SIGUSR1.

            $sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );

addset
    Add a signal to a SigSet object.

            $sigset->addset( &POSIX::SIGUSR2 );

    Returns "undef" on failure.

delset
    Remove a signal from the SigSet object.

            $sigset->delset( &POSIX::SIGUSR2 );

    Returns "undef" on failure.

emptyset
    Initialize the SigSet object to be empty.

            $sigset->emptyset();

    Returns "undef" on failure.

fillset
    Initialize the SigSet object to include all signals.

            $sigset->fillset();

    Returns "undef" on failure.

ismember
    Tests the SigSet object to see if it contains a specific signal.

            if( $sigset->ismember( &POSIX::SIGUSR1 ) ){
                    print "contains SIGUSR1\n";
            }

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_VDISABLE _POSIX_VERSION

SYSTEM CONFIGURATION

Constants
    _SC_ARG_MAX _SC_CHILD_MAX _SC_CLK_TCK _SC_JOB_CONTROL _SC_NGROUPS_MAX _SC_OPEN_MAX _SC_PAGESIZE _SC_SAVED_IDS _SC_STREAM_MAX _SC_TZNAME_MAX _SC_VERSION

ERRNO

Constants
    E2BIG EACCES EADDRINUSE EADDRNOTAVAIL EAFNOSUPPORT EAGAIN EALREADY EBADF 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 ENETRESET 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_tmpname TMP_MAX

TIME

Constants
    CLK_TCK CLOCKS_PER_SEC

UNISTD

Constants
    R_OK SEEK_CUR SEEK_END SEEK_SET STDIN_FILENO STDOUT_FILENO STDERR_FILENO W_OK X_OK

WAIT

Constants
    WNOHANG WUNTRACED

    WNOHANG
        Do not suspend the calling process until a child process changes state but instead return immediately.

    WUNTRACED
        Catch stopped child processes.

Macros
    WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIFSTOPPED WSTOPSIG

    WIFEXITED
        WIFEXITED($?) 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($?) returns the signal the child process terminated for (only meaningful if WIFSIGNALED($?) 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)