=item Keywords related to scoping
-C<caller>, C<import>, C<local>, C<my>, C<package>, C<use>
+C<caller>, C<import>, C<local>, C<my>, C<our>, C<package>, C<use>
=item Miscellaneous functions
-C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<reset>,
+C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<our>, C<reset>,
C<scalar>, C<undef>, C<wantarray>
=item Functions for processes and process groups
=item Functions new in perl5
C<abs>, C<bless>, C<chomp>, C<chr>, C<exists>, C<formline>, C<glob>,
-C<import>, C<lc>, C<lcfirst>, C<map>, C<my>, C<no>, C<prototype>, C<qx>,
-C<qw>, C<readline>, C<readpipe>, C<ref>, C<sub*>, C<sysopen>, C<tie>,
+C<import>, C<lc>, C<lcfirst>, C<map>, C<my>, C<no>, C<our>, C<prototype>,
+C<qx>, C<qw>, C<readline>, C<readpipe>, C<ref>, C<sub*>, C<sysopen>, C<tie>,
C<tied>, C<uc>, C<ucfirst>, C<untie>, C<use>
* - C<sub> was a keyword in perl4, but in perl5 it is an
Another consequence of using binmode() (on some systems) is that
special end-of-file markers will be seen as part of the data stream.
For systems from the Microsoft family this means that if your binary
-data contains C<\cZ>, the I/O subsystem will ragard it as the end of
+data contains C<\cZ>, the I/O subsystem will regard it as the end of
the file, unless you use binmode().
binmode() is not only important for readline() and print() operations,
die() can also be called with a reference argument. If this happens to be
trapped within an eval(), $@ contains the reference. This behavior permits
a more elaborate exception handling implementation using objects that
-maintain arbitary state about the nature of the exception. Such a scheme
+maintain arbitrary state about the nature of the exception. Such a scheme
is sometimes preferable to matching particular string values of $@ using
regular expressions. Here's an example:
(If the entry doesn't exist you get a null list.)
+The exact meaning of the $gcos field varies but it usually contains
+the real name of the user (as opposed to the login name) and other
+information pertaining to the user. Beware, however, that in many
+system users are able to change this information and therefore it
+cannot be trusted and therefore the $gcos is tainted (see
+L<perlsec>). The $passwd and $shell, user's encrypted password and
+login shell, are also tainted, because of the same reason.
+
In scalar context, you get the name, unless the function was a
lookup by name, in which case you get the other thing, whatever it is.
(If the entry doesn't exist you get the undefined value.) For example:
$name = getgrent();
#etc.
-In I<getpw*()> the fields $quota, $comment, and $expire are
-special cases in the sense that in many systems they are unsupported.
-If the $quota is unsupported, it is an empty scalar. If it is
-supported, it usually encodes the disk quota. If the $comment
-field is unsupported, it is an empty scalar. If it is supported it
-usually encodes some administrative comment about the user. In some
-systems the $quota field may be $change or $age, fields that have
-to do with password aging. In some systems the $comment field may
-be $class. The $expire field, if present, encodes the expiration
-period of the account or the password. For the availability and the
-exact meaning of these fields in your system, please consult your
-getpwnam(3) documentation and your F<pwd.h> file. You can also find
-out from within Perl what your $quota and $comment fields mean
-and whether you have the $expire field by using the C<Config> module
-and the values C<d_pwquota>, C<d_pwage>, C<d_pwchange>, C<d_pwcomment>,
-and C<d_pwexpire>. Shadow password files are only supported if your
-vendor has implemented them in the intuitive fashion that calling the
-regular C library routines gets the shadow versions if you're running
-under privilege. Those that incorrectly implement a separate library
-call are not supported.
+In I<getpw*()> the fields $quota, $comment, and $expire are special
+cases in the sense that in many systems they are unsupported. If the
+$quota is unsupported, it is an empty scalar. If it is supported, it
+usually encodes the disk quota. If the $comment field is unsupported,
+it is an empty scalar. If it is supported it usually encodes some
+administrative comment about the user. In some systems the $quota
+field may be $change or $age, fields that have to do with password
+aging. In some systems the $comment field may be $class. The $expire
+field, if present, encodes the expiration period of the account or the
+password. For the availability and the exact meaning of these fields
+in your system, please consult your getpwnam(3) documentation and your
+F<pwd.h> file. You can also find out from within Perl what your
+$quota and $comment fields mean and whether you have the $expire field
+by using the C<Config> module and the values C<d_pwquota>, C<d_pwage>,
+C<d_pwchange>, C<d_pwcomment>, and C<d_pwexpire>. Shadow password
+files are only supported if your vendor has implemented them in the
+intuitive fashion that calling the regular C library routines gets the
+shadow versions if you're running under privilege or if there exists
+the shadow(3) functions as found in System V ( this includes Solaris
+and Linux.) Those systems which implement a proprietary shadow password
+facility are unlikely to be supported.
The $members value returned by I<getgr*()> is a space separated list of
the login names of the members of the group.
indicating December. $year is the number of years since 1900. That
is, $year is C<123> in year 2023. $wday is the day of the week, with
0 indicating Sunday and 3 indicating Wednesday. $yday is the day of
-the year, in the range C<1..365> (or C<1..366> in leap years.)
+the year, in the range C<0..364> (or C<0..365> in leap years.)
Note that the $year element is I<not> simply the last two digits of
the year. If you assume it is, then you create non-Y2K-compliant
print $key, '=', $ENV{$key}, "\n";
}
+The returned values are copies of the original keys in the hash, so
+modifying them will not affect the original hash. Compare L</values>.
+
To sort a hash by value, you'll need to use a C<sort> function.
Here's a descending numeric sort of a hash by its values:
indicating December. $year is the number of years since 1900. That
is, $year is C<123> in year 2023. $wday is the day of the week, with
0 indicating Sunday and 3 indicating Wednesday. $yday is the day of
-the year, in the range C<1..365> (or C<1..366> in leap years.) $isdst
+the year, in the range C<0..364> (or C<0..365> in leap years.) $isdst
is true if the specified time occurs during daylight savings time,
false otherwise.
id, or the undefined value if there is an error. See also C<IPC::SysV>
and C<IPC::Msg> documentation.
-=item msgsnd ID,MSG,FLAGS
-
-Calls the System V IPC function msgsnd to send the message MSG to the
-message queue ID. MSG must begin with the native long integer message
-type, which may be created with C<pack("l!", $type)>. Returns true if
-successful, or false if there is an error. See also C<IPC::SysV> and
-C<IPC::SysV::Msg> documentation.
-
=item msgrcv ID,VAR,SIZE,TYPE,FLAGS
Calls the System V IPC function msgrcv to receive a message from
message queue ID into variable VAR with a maximum message size of
-SIZE. Note that if a message is received, the message type will be
-the first thing in VAR, and the maximum length of VAR is SIZE plus the
-size of the message type. Returns true if successful, or false if
-there is an error. See also C<IPC::SysV> and C<IPC::SysV::Msg> documentation.
+SIZE. Note that when a message is received, the message type as a
+native long integer will be the first thing in VAR, followed by the
+actual message. This packing may be opened with C<unpack("l! a*")>.
+Taints the variable. Returns true if successful, or false if there is
+an error. See also C<IPC::SysV> and C<IPC::SysV::Msg> documentation.
+
+=item msgsnd ID,MSG,FLAGS
+
+Calls the System V IPC function msgsnd to send the message MSG to the
+message queue ID. MSG must begin with the native long integer message
+type, and be followed by the length of the actual message, and finally
+the message itself. This kind of packing can be achieved with
+C<pack("l! a*", $type, $message)>. Returns true if successful,
+or false if there is an error. See also C<IPC::SysV>
+and C<IPC::SysV::Msg> documentation.
=item my EXPR
Opens the file whose filename is given by EXPR, and associates it with
FILEHANDLE. If FILEHANDLE is an expression, its value is used as the
-name of the real filehandle wanted. If EXPR is omitted, the scalar
+name of the real filehandle wanted. (This is considered a symbolic
+reference, so C<use strict 'refs'> should I<not> be in effect.)
+
+If EXPR is omitted, the scalar
variable of the same name as the FILEHANDLE contains the filename.
(Note that lexical variables--those declared with C<my>--will not work
for this purpose; so if you're using C<my>, specify EXPR in your call
open(FOO, "< $file\0");
(this may not work on some bizzare filesystems). One should
-conscientiously choose between the the I<magic> and 3-arguments form
+conscientiously choose between the I<magic> and 3-arguments form
of open():
open IN, $ARGV[0];
follows:
a A string with arbitrary binary data, will be null padded.
- A An ascii string, will be space padded.
+ A An ASCII string, will be space padded.
Z A null terminated (asciz) string, will be null padded.
b A bit string (ascending bit order inside each byte, like vec()).
semid_ds structure or semaphore value array. Returns like C<ioctl>:
the undefined value for error, "C<0 but true>" for zero, or the actual
return value otherwise. The ARG must consist of a vector of native
-short integers, which may may be created with C<pack("s!",(0)x$nsem)>.
+short integers, which may be created with C<pack("s!",(0)x$nsem)>.
See also C<IPC::SysV> and C<IPC::Semaphore> documentation.
=item semget KEY,NSEMS,FLAGS
the C<eval ''>, C<BEGIN {}>, C<INIT {}>, C<CHECK {}>, and C<END {}>
constructs.
-See also C<unshift>, C<push>, and C<pop>. C<Shift()> and C<unshift> do the
+See also C<unshift>, C<push>, and C<pop>. C<shift()> and C<unshift> do the
same thing to the left end of an array that C<pop> and C<push> do to the
right end.
hold the data read. When writing, if STRING is too long, only SIZE
bytes are used; if STRING is too short, nulls are written to fill out
SIZE bytes. Return true if successful, or false if there is an error.
-See also C<IPC::SysV> documentation and the C<IPC::Shareable> module
-from CPAN.
+shmread() taints the variable. See also C<IPC::SysV> documentation and
+the C<IPC::Shareable> module from CPAN.
=item shutdown SOCKET,HOW
and the S_IF* functions are
- S_IFMODE($mode) the part of $mode containg the permission bits
+ S_IFMODE($mode) the part of $mode containing the permission bits
and the setuid/setgid/sticky bits
S_IFMT($mode) the part of $mode containing the file type
be the same order as either the C<keys> or C<each> function would
produce on the same (unmodified) hash.
-Note that you cannot modify the values of a hash this way, because the
-returned list is just a copy. You need to use a hash slice for that,
-since it's lvaluable in a way that values() is not.
+Note that the values are not copied, which means modifying them will
+modify the contents of the hash:
- for (values %hash) { s/foo/bar/g } # FAILS!
- for (@hash{keys %hash}) { s/foo/bar/g } # ok
+ for (values %hash) { s/foo/bar/g } # modifies %hash values
+ for (@hash{keys %hash}) { s/foo/bar/g } # same
As a side effect, calling values() resets the HASH's internal iterator.
See also C<keys>, C<each>, and C<sort>.
projects / p5sagit/p5-mst-13.2.git / blobdiff