=head1 NAME
POSIX - Perl interface to IEEE Std 1003.1
=head1 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
=head1 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 C 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 L 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.
=head1 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.
=head1 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.
=head1 FUNCTIONS
=over 8
=item _exit
This is identical to the C function C<_exit>.
=item abort
This is identical to the C function C.
=item abs
This is identical to Perl's builtin C function.
=item access
Determines the accessibility of a file.
if( POSIX::access( "/", &POSIX::R_OK ) ){
print "have read permission\n";
}
Returns C on failure.
=item acos
This is identical to the C function C.
=item alarm
This is identical to Perl's builtin C function.
=item asctime
This is identical to the C function C.
=item asin
This is identical to the C function C.
=item assert
Unimplemented.
=item atan
This is identical to the C function C.
=item atan2
This is identical to Perl's builtin C function.
=item atexit
atexit() is C-specific: use END {} instead.
=item atof
atof() is C-specific.
=item atoi
atoi() is C-specific.
=item atol
atol() is C-specific.
=item bsearch
bsearch() not supplied.
=item calloc
calloc() is C-specific.
=item ceil
This is identical to the C function C.
=item chdir
This is identical to Perl's builtin C function.
=item chmod
This is identical to Perl's builtin C function.
=item chown
This is identical to Perl's builtin C function.
=item clearerr
Use method C<:handle::clearerr> instead.
=item clock
This is identical to the C function C.
=item close
Close the file. This uses file descriptors such as those obtained by calling
C<:open>.
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
POSIX::close( $fd );
Returns C on failure.
=item closedir
This is identical to Perl's builtin C function.
=item cos
This is identical to Perl's builtin C function.
=item cosh
This is identical to the C function C.
=item creat
Create a new file. This returns a file descriptor like the ones returned by
C<:open>. Use C<:close> to close the file.
$fd = POSIX::creat( "foo", 0611 );
POSIX::close( $fd );
=item ctermid
Generates the path name for the controlling terminal.
$path = POSIX::ctermid();
=item ctime
This is identical to the C function C.
=item cuserid
Get the character login name of the user.
$name = POSIX::cuserid();
=item difftime
This is identical to the C function C.
=item div
div() is C-specific.
=item dup
This is similar to the C function C.
This uses file descriptors such as those obtained by calling
C<:open>.
Returns C on failure.
=item dup2
This is similar to the C function C.
This uses file descriptors such as those obtained by calling
C<:open>.
Returns C on failure.
=item errno
Returns the value of errno.
$errno = POSIX::errno();
=item execl
execl() is C-specific.
=item execle
execle() is C-specific.
=item execlp
execlp() is C-specific.
=item execv
execv() is C-specific.
=item execve
execve() is C-specific.
=item execvp
execvp() is C-specific.
=item exit
This is identical to Perl's builtin C function.
=item exp
This is identical to Perl's builtin C function.
=item fabs
This is identical to Perl's builtin C function.
=item fclose
Use method C<:handle::close> instead.
=item fcntl
This is identical to Perl's builtin C function.
=item fdopen
Use method C<:handle::new_from_fd> instead.
=item feof
Use method C<:handle::eof> instead.
=item ferror
Use method C<:handle::error> instead.
=item fflush
Use method C<:handle::flush> instead.
=item fgetc
Use method C<:handle::getc> instead.
=item fgetpos
Use method C<:seekable::getpos> instead.
=item fgets
Use method C<:handle::gets> instead.
=item fileno
Use method C<:handle::fileno> instead.
=item floor
This is identical to the C function C.
=item fmod
This is identical to the C function C.
=item fopen
Use method C<:file::open> instead.
=item fork
This is identical to Perl's builtin C function.
=item fpathconf
Retrieves the value of a configurable limit on a file or directory. This
uses file descriptors such as those obtained by calling C<:open>.
The following will determine the maximum length of the longest allowable
pathname on the filesystem which holds C.
$fd = POSIX::open( "/tmp/foo", &POSIX::O_RDONLY );
$path_max = POSIX::fpathconf( $fd, &POSIX::_PC_PATH_MAX );
Returns C on failure.
=item fprintf
fprintf() is C-specific--use printf instead.
=item fputc
fputc() is C-specific--use print instead.
=item fputs
fputs() is C-specific--use print instead.
=item fread
fread() is C-specific--use read instead.
=item free
free() is C-specific.
=item freopen
freopen() is C-specific--use open instead.
=item frexp
Return the mantissa and exponent of a floating-point number.
($mantissa, $exponent) = POSIX::frexp( 3.14 );
=item fscanf
fscanf() is C-specific--use and regular expressions instead.
=item fseek
Use method C<:seekable::seek> instead.
=item fsetpos
Use method C<:seekable::setpos> instead.
=item fstat
Get file status. This uses file descriptors such as those obtained by
calling C<:open>. The data returned is identical to the data from
Perl's builtin C function.
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
@stats = POSIX::fstat( $fd );
=item ftell
Use method C<:seekable::tell> instead.
=item fwrite
fwrite() is C-specific--use print instead.
=item getc
This is identical to Perl's builtin C function.
=item getchar
Returns one character from STDIN.
=item getcwd
Returns the name of the current working directory.
=item getegid
Returns the effective group id.
=item getenv
Returns the value of the specified enironment variable.
=item geteuid
Returns the effective user id.
=item getgid
Returns the user's real group id.
=item getgrgid
This is identical to Perl's builtin C function.
=item getgrnam
This is identical to Perl's builtin C function.
=item getgroups
Returns the ids of the user's supplementary groups.
=item getlogin
This is identical to Perl's builtin C function.
=item getpgrp
This is identical to Perl's builtin C function.
=item getpid
Returns the process's id.
=item getppid
This is identical to Perl's builtin C function.
=item getpwnam
This is identical to Perl's builtin C function.
=item getpwuid
This is identical to Perl's builtin C function.
=item gets
Returns one line from STDIN.
=item getuid
Returns the user's id.
=item gmtime
This is identical to Perl's builtin C function.
=item isalnum
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isalpha
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isatty
Returns a boolean indicating whether the specified filehandle is connected
to a tty.
=item iscntrl
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isdigit
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isgraph
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item islower
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isprint
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item ispunct
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isspace
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isupper
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item isxdigit
This is identical to the C function, except that it can apply to a single
character or to a whole string.
=item kill
This is identical to Perl's builtin C function.
=item labs
labs() is C-specific, use abs instead.
=item ldexp
This is identical to the C function C.
=item ldiv
ldiv() is C-specific, use / and int instead.
=item link
This is identical to Perl's builtin C function.
=item localeconv
Get numeric formatting information. Returns a reference to a hash
containing the current locale formatting values.
The database for the B (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";
=item localtime
This is identical to Perl's builtin C function.
=item log
This is identical to Perl's builtin C function.
=item log10
This is identical to the C function C.
=item longjmp
longjmp() is C-specific: use die instead.
=item lseek
Move the file's read/write position. This uses file descriptors such as
those obtained by calling C<:open>.
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
$off_t = POSIX::lseek( $fd, 0, &POSIX::SEEK_SET );
Returns C on failure.
=item malloc
malloc() is C-specific.
=item mblen
This is identical to the C function C.
=item mbstowcs
This is identical to the C function C.
=item mbtowc
This is identical to the C function C.
=item memchr
memchr() is C-specific, use index() instead.
=item memcmp
memcmp() is C-specific, use eq instead.
=item memcpy
memcpy() is C-specific, use = instead.
=item memmove
memmove() is C-specific, use = instead.
=item memset
memset() is C-specific, use x instead.
=item mkdir
This is identical to Perl's builtin C function.
=item mkfifo
This is similar to the C function C.
Returns C on failure.
=item 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 (C), weekday (C), and yearday (C) begin at zero.
I.e. January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1. The
year (C) is given in years since 1900. I.e. The year 1995 is 95; the
year 2001 is 101. Consult your system's C 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 C on failure.
=item modf
Return the integral and fractional parts of a floating-point number.
($fractional, $integral) = POSIX::modf( 3.14 );
=item nice
This is similar to the C function C.
Returns C on failure.
=item offsetof
offsetof() is C-specific.
=item open
Open a file for reading for writing. This returns file descriptors, not
Perl filehandles. Use C<: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 C on failure.
=item opendir
Open a directory for reading.
$dir = POSIX::opendir( "/tmp" );
@files = POSIX::readdir( $dir );
POSIX::closedir( $dir );
Returns C on failure.
=item 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 C.
$path_max = POSIX::pathconf( "/tmp", &POSIX::_PC_PATH_MAX );
Returns C on failure.
=item pause
This is similar to the C function C.
Returns C on failure.
=item perror
This is identical to the C function C.
=item pipe
Create an interprocess channel. This returns file descriptors like those
returned by C<:open>.
($fd0, $fd1) = POSIX::pipe();
POSIX::write( $fd0, "hello", 5 );
POSIX::read( $fd1, $buf, 5 );
=item pow
Computes $x raised to the power $exponent.
$ret = POSIX::pow( $x, $exponent );
=item printf
Prints the specified arguments to STDOUT.
=item putc
putc() is C-specific--use print instead.
=item putchar
putchar() is C-specific--use print instead.
=item puts
puts() is C-specific--use print instead.
=item qsort
qsort() is C-specific, use sort instead.
=item raise
Sends the specified signal to the current process.
=item rand
rand() is non-portable, use Perl's rand instead.
=item read
Read from a file. This uses file descriptors such as those obtained by
calling C<:open>. If the buffer C 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 C on failure.
=item readdir
This is identical to Perl's builtin C function.
=item realloc
realloc() is C-specific.
=item remove
This is identical to Perl's builtin C function.
=item rename
This is identical to Perl's builtin C function.
=item rewind
Seeks to the beginning of the file.
=item rewinddir
This is identical to Perl's builtin C function.
=item rmdir
This is identical to Perl's builtin C function.
=item scanf
scanf() is C-specific--use and regular expressions instead.
=item setgid
Sets the real group id for this process.
=item setjmp
setjmp() is C-specific: use eval {} instead.
=item setlocale
Modifies and queries program's locale.
The following will set the traditional UNIX system locale behavior
(the second argument C).
$loc = POSIX::setlocale( &POSIX::LC_ALL, "C" );
The following will query (the missing second argument) the current
LC_CTYPE category.
$loc = POSIX::setlocale( &POSIX::LC_CTYPE);
The following will set the LC_CTYPE behaviour according to the locale
environment variables (the second argument C).
Please see your systems L documentation for the locale
environment variables' meaning or consult L.
$loc = POSIX::setlocale( &POSIX::LC_CTYPE, "");
The following will set the LC_COLLATE behaviour to Argentinian
Spanish. B: The naming and availability of locales depends on
your operating system. Please consult L for how to find
out which locales are available in your system.
$loc = POSIX::setlocale( &POSIX::LC_ALL, "es_AR.ISO8859-1" );
=item setpgid
This is similar to the C function C.
Returns C on failure.
=item setsid
This is identical to the C function C.
=item setuid
Sets the real user id for this process.
=item sigaction
Detailed signal management. This uses C<:sigaction> objects for the
C and C arguments. Consult your system's C
manpage for details.
Synopsis:
sigaction(sig, action, oldaction = 0)
Returns C on failure.
=item siglongjmp
siglongjmp() is C-specific: use die instead.
=item sigpending
Examine signals that are blocked and pending. This uses C<:sigset>
objects for the C argument. Consult your system's C
manpage for details.
Synopsis:
sigpending(sigset)
Returns C on failure.
=item sigprocmask
Change and/or examine calling process's signal mask. This uses
C<:sigset> objects for the C and C arguments.
Consult your system's C manpage for details.
Synopsis:
sigprocmask(how, sigset, oldsigset = 0)
Returns C on failure.
=item sigsetjmp
sigsetjmp() is C-specific: use eval {} instead.
=item sigsuspend
Install a signal mask and suspend process until signal arrives. This uses
C<:sigset> objects for the C argument. Consult your
system's C manpage for details.
Synopsis:
sigsuspend(signal_mask)
Returns C on failure.
=item sin
This is identical to Perl's builtin C function.
=item sinh
This is identical to the C function C.
=item sleep
This is identical to Perl's builtin C function.
=item sprintf
This is identical to Perl's builtin C function.
=item sqrt
This is identical to Perl's builtin C function.
=item srand
srand().
=item sscanf
sscanf() is C-specific--use regular expressions instead.
=item stat
This is identical to Perl's builtin C function.
=item strcat
strcat() is C-specific, use .= instead.
=item strchr
strchr() is C-specific, use index() instead.
=item strcmp
strcmp() is C-specific, use eq instead.
=item strcoll
This is identical to the C function C.
=item strcpy
strcpy() is C-specific, use = instead.
=item strcspn
strcspn() is C-specific, use regular expressions instead.
=item strerror
Returns the error string for the specified errno.
=item 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 (C), weekday (C), and yearday (C) begin at zero.
I.e. January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1. The
year (C) is given in years since 1900. I.e., the year 1995 is 95; the
year 2001 is 101. Consult your system's C manpage for details
about these and the other arguments. The given arguments are made consistent
by calling C before calling your system's C function.
The string for Tuesday, December 12, 1995.
$str = POSIX::strftime( "%A, %B %d, %Y", 0, 0, 0, 12, 11, 95, 2 );
print "$str\n";
=item strlen
strlen() is C-specific, use length instead.
=item strncat
strncat() is C-specific, use .= instead.
=item strncmp
strncmp() is C-specific, use eq instead.
=item strncpy
strncpy() is C-specific, use = instead.
=item stroul
stroul() is C-specific.
=item strpbrk
strpbrk() is C-specific.
=item strrchr
strrchr() is C-specific, use rindex() instead.
=item strspn
strspn() is C-specific.
=item strstr
This is identical to Perl's builtin C function.
=item 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 I 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.
=item strtok
strtok() is C-specific.
=item 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 I 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.
=item strtoul
String to unsigned (long) integer translation. strtoul is identical
to strtol except that strtoul only parses unsigned integers. See
I for details.
Note: Some vendors supply strtod and strtol but not strtoul.
Other vendors that do suply strtoul parse "-1" as a valid value.
=item strxfrm
String transformation. Returns the transformed string.
$dst = POSIX::strxfrm( $src );
=item 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 C on failure.
=item system
This is identical to Perl's builtin C function.
=item tan
This is identical to the C function C.
=item tanh
This is identical to the C function C.
=item tcdrain
This is similar to the C function C.
Returns C on failure.
=item tcflow
This is similar to the C function C.
Returns C on failure.
=item tcflush
This is similar to the C function C.
Returns C on failure.
=item tcgetpgrp
This is identical to the C function C.
=item tcsendbreak
This is similar to the C function C.
Returns C on failure.
=item tcsetpgrp
This is similar to the C function C.
Returns C on failure.
=item time
This is identical to Perl's builtin C