$rec = join(':', $login,$passwd,$uid,$gid,$gcos,$home,$shell);
-See L</split>.
+Beware that unlike C<split>, C<join> doesn't take a pattern as its
+first argument. Compare L</split>.
=item keys HASH
=item my EXPR
+=item my EXPR : ATTRIBUTES
+
A C<my> declares the listed variables to be local (lexically) to the
enclosing block, file, or C<eval>. If
more than one value is listed, the list must be placed in parentheses. See
for integer
l interpret integer as C type "long" or "unsigned long"
h interpret integer as C type "short" or "unsigned short"
+ If no flags, interpret integer as C type "int" or "unsigned"
There is also one Perl-specific flag:
If Perl understands "quads" (64-bit integers) (this requires
either that the platform natively supports quads or that Perl
-has been specifically compiled to support quads), the flags
+has been specifically compiled to support quads), the characters
d u o x X b i D U O
=item sub NAME BLOCK
This is subroutine definition, not a real function I<per se>. With just a
-NAME (and possibly prototypes), it's just a forward declaration. Without
-a NAME, it's an anonymous function declaration, and does actually return a
-value: the CODE ref of the closure you just created. See L<perlsub> and
-L<perlref> for details.
+NAME (and possibly prototypes or attributes), it's just a forward declaration.
+Without a NAME, it's an anonymous function declaration, and does actually
+return a value: the CODE ref of the closure you just created. See L<perlsub>
+and L<perlref> for details.
=item substr EXPR,OFFSET,LENGTH,REPLACEMENT
The possible values and flag bits of the MODE parameter are
system-dependent; they are available via the standard module C<Fcntl>.
+See the documentation of your operating system's C<open> to see which
+values and flag bits are available. You may combine several flags
+using the C<|>-operator.
+
+Some of the most common values are C<O_RDONLY> for opening the file in
+read-only mode, C<O_WRONLY> for opening the file in write-only mode,
+and C<O_RDWR> for opening the file in read-write mode, and.
+
For historical reasons, some values work on almost every system
supported by perl: zero means read-only, one means write-only, and two
means read/write. We know that these values do I<not> work under
OS/390 & VM/ESA Unix and on the Macintosh; you probably don't want to
-use them in new code.
+se them in new code, use thhe constants discussed in the preceding
+paragraph.
If the file named by FILENAME does not exist and the C<open> call creates
it (typically because MODE includes the C<O_CREAT> flag), then the value of
These permission values need to be in octal, and are modified by your
process's current C<umask>.
+In many systems the C<O_EXCL> flag is available for opening files in
+exclusive mode. This is B<not> locking: exclusiveness means here that
+if the file already exists, sysopen() fails. The C<O_EXCL> wins
+C<O_TRUNC>.
+
+Sometimes you may want to truncate an already-existing file: C<O_TRUNC>.
+
You should seldom if ever use C<0644> as argument to C<sysopen>, because
that takes away the user's option to have a more permissive umask.
Better to omit it. See the perlfunc(1) entry on C<umask> for more
use integer;
use diagnostics;
- use sigtrap qw(SEGV BUS);
- use strict qw(subs vars refs);
- use subs qw(afunc blurfl);
- use warning qw(all);
+ use sigtrap qw(SEGV BUS);
+ use strict qw(subs vars refs);
+ use subs qw(afunc blurfl);
+ use warnings qw(all);
Some of these pseudo-modules import semantics into the current
block scope (like C<strict> or C<integer>, unlike ordinary modules,
no integer;
no strict 'refs';
- no warning;
+ no warnings;
If no C<unimport> method can be found the call fails with a fatal error.
=item vec EXPR,OFFSET,BITS
Treats the string in EXPR as a vector of unsigned integers, and
-returns the value of the bit field specified by OFFSET. BITS specifies
-the number of bits that are reserved for each entry in the bit
-vector. This must be a power of two from 1 to 32. C<vec> may also be
-assigned to, in which case parentheses are needed to give the expression
-the correct precedence as in
+returns the value of the bit field specified by OFFSET. BITS
+specifies the number of bits that are reserved for each entry in the
+bit vector. This must be a power of two from 1 to 32 (or 64, if your
+platform supports that).
+
+C<vec> may also be assigned to, in which case parentheses are needed
+to give the expression the correct precedence as in
vec($image, $max_x * $x + $y, 8) = 3;
Vectors created with C<vec> can also be manipulated with the logical
-operators C<|>, C<&>, and C<^>, which will assume a bit vector operation is
-desired when both operands are strings. See L<perlop/"Bitwise String Operators">.
+operators C<|>, C<&>, and C<^>, which will assume a bit vector
+operation is desired when both operands are strings.
+See L<perlop/"Bitwise String Operators">.
The following code will build up an ASCII string saying C<'PerlPerlPerl'>.
The comments show the string after each step. Note that this code works