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.

Everything is exported by default with the exception of any POSIX functions with the same name as a built-in Perl function, such as "abs", "alarm", "rmdir", "write", etc.., which will be exported only if you ask for them explicitly. This is an unfortunate backwards compatibility feature. You can stop the exporting by saying "use POSIX ()" and then use the fully qualified names (ie. "POSIX::SEEK_END").

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.

Note that when using threads and in Linux this is not a good way to exit a thread because in Linux processes and threads are kind of the same thing (Note: while this is the situation in early 2003 there are projects under way to have threads with more POSIXly semantics in Linux). If you want not to return from a thread, detach the thread.

abort

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

abs

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

access

Determines the accessibility of a file.

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

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

acos

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

alarm

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

asctime

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

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

and it is called thusly

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

The $mon is zero-based: January equals 0. The $year is 1900-based: 2001 equals 101. $wday and $yday default to zero (and are usually ignored anyway), and $isdst defaults to -1.

asin

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

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 "/var/foo".

        $fd = POSIX::open( "/var/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 );
    

fsync

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

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 environment variable. The same information is available through the %ENV array.

geteuid

Returns the effective user identifier. Identical to Perl's builtin $> variable, see "$EUID" in perlvar.

getgid

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

getgrgid

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

getgrnam

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

getgroups

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

getlogin

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

getpgrp

This is identical to Perl's builtin "getpgrp()" function for returning the process group identifier of the current process, see "getpgrp" in perlfunc.

getpid

Returns the process identifier. Identical to Perl's builtin variable $$, see "$PID" in perlvar.

getppid

This is identical to Perl's builtin "getppid()" function for returning the process identifier of the parent process of the current process , see "getppid" in perlfunc.

getpwnam

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

getpwuid

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

gets

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

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

getuid

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

gmtime

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

isalnum

This is identical to the C function, except that it can apply to a single character or to a whole string. Note that locale settings may affect what characters are considered "isalnum". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isalpha". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "iscntrl". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isdigit" (unlikely, but still possible). Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isgraph". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "islower". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isprint". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "ispunct". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isspace". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isupper". Does not work on Unicode characters code point 256 or higher. 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. Note that locale settings may affect what characters are considered "isxdigit" (unlikely, but still possible). Does not work on Unicode characters code point 256 or higher. 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, though for "mkfifo" you must specify the $mode.

mktime

Convert date/time info to a calendar time.

Synopsis:

        mktime(sec, min, hour, mday, mon, year, wday = 0, yday = 0, isdst = -1)
    

The month ("mon"), weekday ("wday"), and yearday ("yday") begin at zero. I.e. January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1. The year ("year") is given in years since 1900. I.e. The year 1995 is 95; the year 2001 is 101. Consult your system's "mktime()" manpage for details about these and the other arguments.

Calendar time for December 12, 1995, at 10:30 am.

        $time_t = POSIX::mktime( 0, 30, 10, 12, 11, 95 );
        print "Date = ", POSIX::ctime($time_t);
    

Returns "undef" on failure.

modf

Return the integral and fractional parts of a floating-point number.

        ($fractional, $integral) = POSIX::modf( 3.14 );
    

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( "/var" );
        @files = POSIX::readdir( $dir );
        POSIX::closedir( $dir );
    

Returns "undef" on failure.

pathconf

Retrieves the value of a configurable limit on a file or directory.

The following will determine the maximum length of the longest allowable pathname on the filesystem which holds "/var".

        $path_max = POSIX::pathconf( "/var", &POSIX::_PC_PATH_MAX );
    

Returns "undef" on failure.

pause

This is similar to the C function "pause()", which suspends the execution of the current process until a signal is received.

Returns "undef" on failure.

perror

This is identical to the C function "perror()", which outputs to the standard error stream the specified message followed by ": " and the current error string. Use the "warn()" function and the $! variable instead, see "warn" in perlfunc and "$ERRNO" in perlvar.

pipe

Create an interprocess channel. This returns file descriptors like those returned by "POSIX::open".

        my ($read, $write) = POSIX::pipe();
        POSIX::write( $write, "hello", 5 );
        POSIX::read( $read, $buf, 5 );
    

See also "pipe" in perlfunc.

pow

Computes $x raised to the power $exponent.

        $ret = POSIX::pow( $x, $exponent );
    

You can also use the "**" operator, see perlop.

printf

Formats and prints the specified arguments to STDOUT. See also "printf" in perlfunc.

putc

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 $) variable, see "$EGID" in perlvar, except that the latter will change only the real user identifier, and that the setgid() uses only a single numeric argument, as opposed to a space-separated list of numbers.

setjmp

"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 (the oldaction can also be just a hash reference). Consult your system's "sigaction" manpage for details, see also "POSIX::SigRt".

Synopsis:

        sigaction(signal, action, oldaction = 0)
    

Returns "undef" on failure. The "signal" must be a number (like SIGHUP), not a string (like "SIGHUP"), though Perl does try hard to understand you.

If you use the SA_SIGINFO flag, the signal handler will in addition to the first argument, the signal name, also receive a second argument, a hash reference, inside which are the following keys with the following semantics, as defined by POSIX/SUSv3:

    signo       the signal number
    errno       the error number
    code        if this is zero or less, the signal was sent by
                a user process and the uid and pid make sense,
                otherwise the signal was sent by the kernel
    

The following are also defined by POSIX/SUSv3, but unfortunately not very widely implemented:

    pid         the process id generating the signal
    uid         the uid of the process id generating the signal
    status      exit value or signal for SIGCHLD
    band        band event for SIGPOLL
    

A third argument is also passed to the handler, which contains a copy of the raw binary contents of the siginfo structure: if a system has some non-POSIX fields, this third argument is where to unpack() them from.

Note that not all siginfo values make sense simultaneously (some are valid only for certain signals, for example), and not all values make sense from Perl perspective, you should to consult your system's "sigaction" and possibly also "siginfo" documentation.

siglongjmp

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 significant difference, however: "POSIX::sleep()" returns the number of unslept seconds, while the "CORE::sleep()" returns the number of slept seconds.

sprintf

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

sqrt

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

srand

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

sscanf

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

stat

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

strcat

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 (C89, to play safe). These are "aAbBcdHIjmMpSUwWxXyYZ%". But even then, the results of some of the conversion specifiers are non-portable. For example, the specifiers "aAbBcpZ" change according to the locale settings of the user, and both how to set locales (the locale names) and what output to expect are non-standard. The specifier "c" changes according to the timezone settings of the user and the timezone computation rules of the operating system. The "Z" specifier is notoriously unportable since the names of timezones are non-standard. Sticking to the numeric specifiers is the safest route.

The given arguments are made consistent as though by calling "mktime()" before calling your system's "strftime()" function, except that the "isdst" value is not affected.

The string for Tuesday, December 12, 1995.

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

strlen

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 argument stream.

Returns "undef" on failure.

tcgetpgrp

This is identical to the C function "tcgetpgrp()" for returning the process group identifier of the foreground process group of the controlling terminal.

tcsendbreak

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

Returns "undef" on failure.

tcsetpgrp

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

Returns "undef" on failure.

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( $fd, $buf, 5 );
    

Returns "undef" on failure.

See also "syswrite" in perlfunc.

CLASSES¶

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

Macros

WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIFSTOPPED WSTOPSIG