appa.htm

《Perl 5 Unreleased》

is specified, the last file handle used in a statement is assumed.
The <TT><FONT FACE="Courier">FILEHANDLE</FONT></TT> may be an
expression whose value gives the real file handle. This function
should not be used for reading from the console. If used in a
<TT><FONT FACE="Courier">while (&lt;&gt;)</FONT></TT> loop, the
<TT><FONT FACE="Courier">eof()</FONT></TT> call is valid for each
file being read.
<H4><TT><FONT FACE="Courier">eval <BR>
eval Expression<BR>
eval code block</FONT></TT></H4>
<P>
Evaluates the expression passed to it just like a Perl program
and returns the value of the last expression evaluated. A return
statement may be used in an <TT><FONT FACE="Courier">eval()</FONT></TT>
statement. The call returns an undefined value if there is a runtime
error or if the <TT><FONT FACE="Courier">die()</FONT></TT> call
is made. The <TT><FONT FACE="Courier">$@</FONT></TT> variable
is set to the error message. If there was no error, <TT><FONT FACE="Courier">$@</FONT></TT>
is set to <TT><FONT FACE="Courier">null</FONT></TT>. The <TT><FONT FACE="Courier">eval()</FONT></TT>
call uses <TT><FONT FACE="Courier">$_</FONT></TT> if no expression
is given. The final semicolon in a code block is not necessary.
<H4><TT><FONT FACE="Courier">exec command [args ... ]</FONT></TT>
</H4>
<P>
The <TT><FONT FACE="Courier">exec()</FONT></TT> function executes
a system command and does not return. This call is generally made
after a <TT><FONT FACE="Courier">fork()</FONT></TT> call. The
arguments to the <TT><FONT FACE="Courier">exec</FONT></TT> command
include the command to execute in the first argument, followed
by any arguments to that command.
<H4><TT><FONT FACE="Courier">exists Expression</FONT></TT></H4>
<P>
Checks if a key exists in a hash. Returns <TT><FONT FACE="Courier">true</FONT></TT>
if the key does exist, and <TT><FONT FACE="Courier">null</FONT></TT>
if it does not.
<H4><TT><FONT FACE="Courier">exit Expression</FONT></TT></H4>
<P>
Exits with the value from the <TT><FONT FACE="Courier">Expression</FONT></TT>
evaluation. If no <TT><FONT FACE="Courier">Expression</FONT></TT>
is given, it exits with a value of <TT><FONT FACE="Courier">0</FONT></TT>.
<H4><TT><FONT FACE="Courier">exp Expression</FONT></TT></H4>
<P>
Returns the natural logarithm base to the power of <TT><FONT FACE="Courier">Expression</FONT></TT>.
Uses <TT><FONT FACE="Courier">$_</FONT></TT> if no <TT><FONT FACE="Courier">Expression</FONT></TT>
is given.
<H4><TT><FONT FACE="Courier">fcntl FILEHANDLE,function,scalar</FONT></TT>
</H4>
<P>
Implements the <TT><FONT FACE="Courier">fcntl(2)</FONT></TT> function
and requires the <TT><FONT FACE="Courier">Fcntl</FONT></TT> module.
<H4><TT><FONT FACE="Courier">fileno FILEHANDLE</FONT></TT></H4>
<P>
Returns the file descriptor <TT><FONT FACE="Courier">id</FONT></TT>
for a file handle and is used with the <TT><FONT FACE="Courier">select()</FONT></TT>
call. The <TT><FONT FACE="Courier">FILEHANDLE</FONT></TT> may
be an expression whose value would be used as the name of the
file handle.
<H4><TT><FONT FACE="Courier">flock FILEHANDLE,operation</FONT></TT>
</H4>
<P>
Calls the system function <TT><FONT FACE="Courier">flock(2)</FONT></TT>
on <TT><FONT FACE="Courier">FILEHANDLE</FONT></TT>. Returns <TT><FONT FACE="Courier">true</FONT></TT>
on success and <TT><FONT FACE="Courier">false</FONT></TT> on failure.
The <TT><FONT FACE="Courier">flock</FONT></TT> function locks
files, not records within files-but it's portable across platforms,
especially if the locked files exist across the network.
<H4><TT><FONT FACE="Courier">fork</FONT></TT></H4>
<P>
This is a <TT><FONT FACE="Courier">fork(2)</FONT></TT> system
call. Upon return, the parent process gets the child <TT><FONT FACE="Courier">pid</FONT></TT>,
and the child process gets a <TT><FONT FACE="Courier">0</FONT></TT>.
The parent process gets <TT><FONT FACE="Courier">undef</FONT></TT>
in case of errors. It's a good idea to set <TT><FONT FACE="Courier">$|</FONT></TT>
to <TT><FONT FACE="Courier">1</FONT></TT> before a <TT><FONT FACE="Courier">fork</FONT></TT>
or to call the <TT><FONT FACE="Courier">autoflush(FILEHANDLE)</FONT></TT>
function to flush any pending output before the <TT><FONT FACE="Courier">fork</FONT></TT>
call because buffers are not automatically flushed by <TT><FONT FACE="Courier">fork()</FONT></TT>.
<H4><TT><FONT FACE="Courier">format</FONT></TT></H4>
<P>
The <TT><FONT FACE="Courier">format</FONT></TT> command. <A HREF="ch19.htm" tppabs="http://www.mcp.com/815097600/0-672/0-672-30891-6/ch19.htm" >See Chapter 19</A>,
&quot;Generating Reports.&quot;
<H4><TT><FONT FACE="Courier">getc<BR>
getc FILEHANDLE</FONT></TT></H4>
<P>
Does a <TT><FONT FACE="Courier">getc()</FONT></TT> I/O call to
get the next character from the input file specified in <TT><FONT FACE="Courier">FILEHANDLE</FONT></TT>.
It returns <TT><FONT FACE="Courier">null</FONT></TT> if at end
of file. If no <TT><FONT FACE="Courier">FILEHANDLE</FONT></TT>
is specified, <TT><FONT FACE="Courier">getc</FONT></TT> uses <TT><FONT FACE="Courier">STDIN</FONT></TT>
for input.
<H4><TT><FONT FACE="Courier">getgrgid GID<BR>
getpwuid UID</FONT></TT></H4>
<P>
Gets the password or group file entry from the user or group ID.
Each function performs the same function as the underlying system
call.
<H4><TT><FONT FACE="Courier">gethostbyname name<BR>
getnetbyname name<BR>
getprotobyname name<BR>
getservbyname name,protocol<BR>
gethostbyaddr addr,addressType<BR>
getnetbyaddr addr,addressType</FONT></TT></H4>
<P>
These functions perform the same function as the underlying system
call to return the net structure. See networks(5) in the UNIX
manuals.
<H4><TT><FONT FACE="Courier">getlogin</FONT></TT></H4>
<P>
Gets the current login name from <TT><FONT FACE="Courier">/etc/utmp</FONT></TT>,
if any. It's better to use <TT><FONT FACE="Courier">getpwuid($&lt;)</FONT></TT>.
<H4><TT><FONT FACE="Courier">getpeernam socket</FONT></TT></H4>
<P>
Gets the packed <TT><FONT FACE="Courier">sockaddr</FONT></TT>
structure with the socket address of the remote computer at the
end of a socket connection.
<H4><TT><FONT FACE="Courier">getpgrp pid</FONT></TT></H4>
<P>
Gets the current process group for the specified <TT><FONT FACE="Courier">pid</FONT></TT>.
You can use <TT><FONT FACE="Courier">0</FONT></TT> or <TT><FONT FACE="Courier">null</FONT></TT>
for specifying the current process.
<P>
This function may raise a fatal exception if the underlying system
call is not supported.
<H4><TT><FONT FACE="Courier">getppid</FONT></TT></H4>
<P>
Gets the process ID of the parent process.
<H4><TT><FONT FACE="Courier">getpriority processID<BR>
getpriority UID</FONT></TT></H4>
<P>
Gets the current priority for a process, a process group, or a
user using the <TT><FONT FACE="Courier">getpriority(2)</FONT></TT>
system call. This function may raise a fatal exception if the
underlying system call is not supported.
<H4><TT><FONT FACE="Courier">getprotobynumber number</FONT></TT>
</H4>
<P>
Returns the protocol by number.
<H4><TT><FONT FACE="Courier">getpwent<BR>
getgrent<BR>
gethostent<BR>
getnetent<BR>
getprotoent<BR>
getservent</FONT></TT></H4>
<P>
These functions perform the same function as the underlying system
call.
<H4><TT><FONT FACE="Courier">getpwnam name<BR>
getgrnam name</FONT></TT></H4>
<P>
Gets the password or group file entry given a <TT><FONT FACE="Courier">name</FONT></TT>.
This function performs the same function as the underlying system
call.
<H4><TT><FONT FACE="Courier">getservbyport port, proto</FONT></TT>
</H4>
<P>
This function performs the same function as the underlying system
call. The <TT><FONT FACE="Courier">port</FONT></TT> is the port
number to use for the given protocol in <TT><FONT FACE="Courier">proto</FONT></TT>.
Check out the file <TT><FONT FACE="Courier">/usr/include/net.h</FONT></TT>
for these values.
<H4><TT><FONT FACE="Courier">getsockname SOCKETHANDLE</FONT></TT>
</H4>
<P>
Gets the packed <TT><FONT FACE="Courier">sockaddr</FONT></TT>
structure with the address of the local end of a socket connection.
<H4><TT><FONT FACE="Courier">getsockopt SOCKETHANDLE,level,optname</FONT></TT>
</H4>
<P>
Gets the socket option requested, or is undefined if there is
an error. This function performs the same function as the underlying
system call.
<H4><TT><FONT FACE="Courier">glob Expression</FONT></TT></H4>
<P>
Expands the value of <TT><FONT FACE="Courier">Expression</FONT></TT>
to filenames just like a shell operation.
<H4><TT><FONT FACE="Courier">gmtime Expression</FONT></TT></H4>
<P>
Converts the time value returned by the <TT><FONT FACE="Courier">time()</FONT></TT>
function to a nine-element array adjusted for the standard Greenwich
time zone. All returned array elements are numeric and come straight
out of a struct <TT><FONT FACE="Courier">tm</FONT></TT> defined
in <TT><FONT FACE="Courier">/usr/include/time.h</FONT></TT>.
<H4><TT><FONT FACE="Courier">goto LABEL<BR>
goto Expression<BR>
goto &amp;name</FONT></TT></H4>
<P>
The <TT><FONT FACE="Courier">goto LABEL</FONT></TT> form jumps
to the statement labeled with <TT><FONT FACE="Courier">LABEL</FONT></TT>.
You cannot jump into a subroutine or within a loop. The <TT><FONT FACE="Courier">Expression</FONT></TT>
is used for computed <TT><FONT FACE="Courier">GOTO</FONT></TT>s.
<TT><FONT FACE="Courier">GOTO &amp;name</FONT></TT> substitutes
a call to the named subroutine for the currently running subroutine.
The code returns back from the newly referenced subroutine.
<H4><TT><FONT FACE="Courier">grep Codeblock @list<BR>
grep Expression, @list</FONT></TT></H4>
<P>
Runs <TT><FONT FACE="Courier">grep</FONT></TT> on the <TT><FONT FACE="Courier">Codeblock</FONT></TT>
or <TT><FONT FACE="Courier">Expression</FONT></TT> for each element
of <TT><FONT FACE="Courier">@list</FONT></TT> by setting <TT><FONT FACE="Courier">$_</FONT></TT>
to each element in the <TT><FONT FACE="Courier">@list</FONT></TT>.
The return value is a list of all the elements that matched the
<TT><FONT FACE="Courier">grep</FONT></TT> expression. For example,
<TT><FONT FACE="Courier">@freds = grep(/fred/, @users);</FONT></TT>
gets all the strings with the word <TT><FONT FACE="Courier">fred</FONT></TT>
in <TT><FONT FACE="Courier">@users</FONT></TT>.
<H4><TT><FONT FACE="Courier">hex Expression</FONT></TT></H4>
<P>
Evaluates <TT><FONT FACE="Courier">Expression</FONT></TT> as a
hex string and returns the corresponding decimal number.
<H4><TT><FONT FACE="Courier">import moduleName</FONT></TT></H4>
<P>
Used to import other modules into a program.
<H4><TT><FONT FACE="Courier">index string,substr,[position]</FONT></TT>
</H4>
<P>
Gets the position of the first occurrence of <TT><FONT FACE="Courier">substr</FONT></TT>
in <TT><FONT FACE="Courier">str</FONT></TT> at or after the optional
parameter, <TT><FONT FACE="Courier">position</FONT></TT>. If <TT><FONT FACE="Courier">position</FONT></TT>
is omitted, a search is started from the beginning of the string.
The return value is indexed from <TT><FONT FACE="Courier">0</FONT></TT>
or <TT><FONT FACE="Courier">h</FONT></TT>, the value in the <TT><FONT FACE="Courier">$[</FONT></TT>
variable. Returns <TT><FONT FACE="Courier">-1</FONT></TT> or (<TT><FONT FACE="Courier">$[
- 1</FONT></TT>) if no <TT><FONT FACE="Courier">substr</FONT></TT>
was found.
<H4><TT><FONT FACE="Courier">int Expression</FONT></TT></H4>
<P>
Parses the <TT><FONT FACE="Courier">Expression</FONT></TT> to
return the integer portion. If <TT><FONT FACE="Courier">Expression</FONT></TT>
is omitted, <TT><FONT FACE="Courier">$_</FONT></TT> is used to
parse for integer.
<H4><TT><FONT FACE="Courier">ioctl FILEHANDLE,function,scalar</FONT></TT>
</H4>
<P>
Implements the <TT><FONT FACE="Courier">ioctl(2)</FONT></TT> function.