ch25.htm

this is a book on pearl , simple example with explanation is given here. it could be beneficial for

or an empty list. <TT>$proto</TT>

is the protocol number.<BR>

<B>Definition:</B> Looks in the <TT>/etc/protocols</TT>

system file for the protocol called <TT>NAME</TT>.

<BLOCKQUOTE>

<PRE>

($name, $alias, $proto) = getprotobyname(&quot;IP&quot;);

print(&quot;getprotobyname() /etc/proto [$name, $alias, $proto].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getprotobynumberNUMBER">

getprotobynumber (NUMBER)</A></H3>

<P>

<B>Category:</B> Protocols, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The protocol name associated

with <TT>NUMBER</TT>.<BR>

<B>Return Value in Array Context:</B> (<TT>$name</TT>,

<TT>$aliases</TT>, <TT>$proto</TT>)

or an empty list.<BR>

<B>Definition:</B> Looks in the <TT>/etc/protocols</TT>

system file for <TT>NUMBER</TT>.

<BLOCKQUOTE>

<PRE>

($name, $alias, $proto) = getprotobynumber(0);

print(&quot;getprotobynumber() /etc/protocols [$name, $alias, $proto].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getprotoent">

getprotoent ( )</A></H3>

<P>

<B>Category:</B> Protocols, UNIX<BR>

<B>Return Value:</B> ARRAY. (<TT>$name</TT>,

<TT>$aliases</TT>, <TT>$proto</TT>)

or an empty list.<BR>

<B>Definition:</B> When called repeatedly, <TT>getprotoent()</TT>

iterates over the <TT>/etc/protocols</TT>

system file.

<BLOCKQUOTE>

<PRE>

($name, $alias, $proto) = getprotoent();

print(&quot;getprotoent() Closes /etc/protocols [$name, $alias, $proto].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getpwent">

getpwent ( )</A></H3>

<P>

<B>Category:</B> Password, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The username.<BR>

<B>Return Value in Array Context:</B> ARRAY. (<TT>$name</TT>,

<TT>$passwd</TT>, <TT>$uid</TT>,

<TT>$gid</TT>, <TT>$quota</TT>,

<TT>$comment</TT>, <TT>$gcos</TT>,

<TT>$dir</TT>, <TT>$shell</TT>)

or an empty list.<BR>

<B>Definition:</B> When called repeatedly, <TT>getpwent()</TT>

iterates over the <TT>/etc/passwd</TT>

system file.

<BLOCKQUOTE>

<PRE>

($name, $pass, $uid, $gid, $quota, $name, $gcos, $dir, $shell) = getpwent();

print(&quot;getpwent() /etc/passwd [$dir, $shell].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getpwnamNAME">

getpwnam (NAME)</A></H3>

<P>

<B>Category:</B> Password, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The userid of <TT>NAME</TT>.

<BR>

<B>Return Value in Array Context:</B> (<TT>$name,

$passwd, $uid, $gid, $quota, $comment, $gcos, $dir, $shell</TT>)

or an empty list.<BR>

<B>Definition:</B> Looks in the <TT>/etc/passwd</TT>

system file for <TT>NAME</TT>.

<BLOCKQUOTE>

<PRE>

($name, $pass, $uid, $gid, $quota, $name, 

    $gcos, $dir, $shell) = getpwnam(&quot;root&quot;);

print(&quot;getpwnam() /etc/passwd [$dir, $shell].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getpwuidUID">

getpwuid (UID)</A></H3>

<P>

<B>Category:</B> Password, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The username of <TT>UID</TT>.

<BR>

<B>Return Value in Array Context:</B> (<TT>$name</TT>,

<TT>$passwd</TT>, <TT>$uid</TT>,

<TT>$gid</TT>, <TT>$quota</TT>,

<TT>$comment</TT>, <TT>$gcos</TT>,

<TT>$dir</TT>, <TT>$shell</TT>)

or an empty list.<BR>

<B>Definition:</B> Looks in the <TT>/etc/passwd</TT>

system file for <TT>UID</TT>.

<BLOCKQUOTE>

<PRE>

($name, $pass, $uid, $gid, $quota, $name, 

    $gcos, $dir, $shell) = getpwuid(0);

print(&quot;getpwuid() /etc/passwd [$dir, $shell].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getservbynameNAMEPROTOCOL">

getservbyname (NAME, PROTOCOL)</A></H3>

<P>

<B>Category:</B> Protocol, Service, Socket, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The port number.<BR>

<B>Return Value in Array Context:</B> (<TT>$name</TT>,

<TT>$aliases</TT>, <TT>$port</TT>,

<TT>$proto</TT>) or an empty list.

<BR>

<B>Definition:</B> Gets services by name. Looks in the <TT>/etc/services</TT>

system file.

<BLOCKQUOTE>

<PRE>

($name, $aliases, $port, $protol) = getservbyname(&quot;tcpmux&quot;, &quot;tcp&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getservbyportPORTNUMBERPROTOCOL">

getservbyport (PORT_NUMBER, PROTOCOL)</A></H3>

<P>

<B>Category:</B> Protocol, Service, Socket, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The service name.<BR>

<B>Return Value in Array Context:</B> (<TT>$name</TT>,

<TT>$aliases</TT>, <TT>$port</TT>,

<TT>$proto</TT>) or an empty list.

<BR>

<B>Definition:</B> Gets services by port. Looks in the <TT>/etc/services</TT>

system file.

<BLOCKQUOTE>

<PRE>

($name, $aliases, $port, $protol) = getservbyport(512, &quot;tcp&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getservent">

getservent ( )</A></H3>

<P>

<B>Category:</B> Protocol, Service, Socket, UNIX<BR>

<B>Return Value: </B>in Scalar Context: The next service name.

<BR>

<B>Return Value in Array Context:</B> (<TT>$name</TT>,

<TT>$aliases</TT>, <TT>$port</TT>,

<TT>$proto</TT>) or an empty list.

<BR>

<B>Definition:</B> When called repeatedly, iterates over the <TT>/etc/services</TT>

system file.

<BLOCKQUOTE>

<PRE>

($name, $aliases, $port, $protol) = getservent();

print(&quot;getservent() /etc/servers [$name].\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getsocknameSOCKET">

getsockname (SOCKET)</A></H3>

<P>

<B>Category:</B> Sockets<BR>

<B>Return Value:</B> SCALAR, the packed address of the local end

of the socket.<BR>

<B>Definition:</B> Finds out the address of your script's socket.

<BLOCKQUOTE>

<PRE>

$packedAddr = getsockname(S);

($family, $port, $localAddr) = unpack('S n a4 x8', $packedAddr);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="getsockoptSOCKETLEVELOPTNAME">

getsockopt (SOCKET, LEVEL, OPTNAME)</A></H3>

<P>

<B>Category:</B> Sockets<BR>

<B>Return Value:</B> SCALAR, the socket option requested or the

undefined value.<BR>

<B>Definition:</B> Gets the value of a specified socket option.

<H3><A NAME="globEXPR">

glob (EXPR)</A></H3>

<P>

<B>Category:</B> File<BR>

<B>Return Value:</B> ARRAY, the list of files represented by <TT>EXPR</TT>.

<BR>

<B>Definition:</B> Looks for file name that match <TT>EXPR</TT>.

You can use wildcards in <TT>EXPR</TT>.

<BLOCKQUOTE>

<PRE>

@files = glob(&quot;*.txt&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="gmtimeEXPR">

gmtime ([EXPR])</A></H3>

<P>

<B>Category:</B> Time<BR>

<B>Return Value: </B>in Scalar Context: A string like 'Sat Jul

13 07:34:46 1986' describing <TT>EXPR</TT>.

<BR>

<B>Return Value in Array Context:</B> (<TT>$sec</TT>,

<TT>$min</TT>, <TT>$hour</TT>,

<TT>$mday</TT>, <TT>$mon</TT>,

<TT>$year</TT>, <TT>$wday</TT>,

<TT>$ydat</TT>, <TT>$isdst</TT>).

<BR>

<B>Definition:</B> Breaks <TT>EXPR</TT>

(a number of seconds siNCe 1st Jan 1970) into a 9-element list.

If no argument is used the current time is used. If your system

supports POSIX time zones, the time returned is localized for

the Greenwich Mean Time time zone. Note that <TT>$mon</TT>

ranges from 0..11, <TT>$wday</TT>

ranges from 0..6, and <TT>$year</TT>

does not handle centuries.

<BLOCKQUOTE>

<PRE>

($sec, $min, $hour, $mday, $mon, $year, $wday, $ydat, $isdst) = gmtime();

print &quot;gmtime() 19$year-$mon-$mday\n&quot;;

</PRE>

</BLOCKQUOTE>

<H3><A NAME="grepBLOCKEXPRLIST">

grep (BLOCK | EXPR, LIST)</A></H3>

<P>

<B>Category:</B> Regular Expressions<BR>

<B>Return Value: </B>in Scalar Context: The number of times that

<TT>BLOCK</TT> or <TT>EXPR</TT>

evaluated to true.<BR>

<B>Return Value in Array Context:</B> A list of the elements of

<TT>LIST</TT> that causes <TT>BLOCK</TT>

or <TT>EXPR</TT> to evaluate as true.

<BR>

<B>Definition:</B> Evaluates the expression or block for each

of the elements in <TT>LIST</TT>.

Think of this fuNCtion as having an internal <TT>foreach</TT>

loop. Each element in <TT>LIST</TT>

is assigned to <TT>$_</TT> and then

the block or expression is evaluated. The most common use for

this is with a pattern match operation as the expression, and

a list of strings to be processed. You may be tempted to use <TT>grep()</TT>

as an easy way to interate over an array as shown in the second

example below, <I>don't do this</I>. Use the <TT>map()</TT>

fuNCtion instead.

<BLOCKQUOTE>

<PRE>

# Look for all elements that begin with the letter T.

@a = ('One', 'Two', 'Three', 'Four', 'Five');

print(&quot;grep(), &quot;, grep(/^T/, @a), &quot;\n&quot;);



# Print all elements in a list.

@a = ('One', 'Two', 'Three', 'Four', 'Five');

grep( print(&quot;$_\n&quot;), @a);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="hexEXPR">

hex (EXPR)</A></H3>

<P>

<B>Category:</B> Math, String<BR>

<B>Return Value:</B> SCALAR, the decimal value of <TT>EXPR</TT>.

<BR>

<B>Definition:</B> Converts <TT>EXPR</TT>

from hexadecimal to decimal. For example, <TT>hex('FF0')</TT>

will return <TT>'4080'</TT>. You can

use the string returned as a number because Perl will automatically

convert strings to numbers in numeric contexts.

<BLOCKQUOTE>

<PRE>

print(&quot;hex() &quot;, hex(&quot;ff&quot;), &quot;\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="import">

import ( )</A></H3>

<P>

<B>Category:</B> Miscellaneous<BR>

<B>Return Value:</B> None. <BR>

<B>Definition:</B> This is the only user-defined fuNCtion in this

list. If a module has an <TT>import()</TT>

fuNCtion then the <TT>use()</TT> fuNCtion

will call it as the module is being loaded. You can use the <TT>import()</TT>

fuNCtion to initialize variables, open files, or do any other

setup work.

<H3><A NAME="indexSTRINGSUBSTRINGPOSITION">

index (STRING, SUBSTRING, [POSITION])</A></H3>

<P>

<B>Category:</B> String<BR>

<B>Return Value:</B> SCALAR, the position of the first occurreNCe

of <TT>SUBSTRING</TT> in <TT>STRING</TT>

at or after <TT>POSITION</TT> or -1

if not found.<BR>

<B>Definition:</B> When called repeatedly, you can iterate over

all the occurreNCes of <TT>SUBSTRING</TT>

in <TT>STRING</TT>. The returned value

is an offset from <TT>$[</TT> (which

is normally zero). If <TT>$[</TT>

is altered it will change the way <TT>index()</TT>

works as it will start its search from <TT>$[</TT>

if no position argument is supplied, and it will return <TT>$[

- 1</TT> when there is no match found.

<BLOCKQUOTE>

<PRE>

$answer1 = index(&quot;abcdefghijiklmdef:-)&quot;, &quot;def&quot;);

$answer2 = index(&quot;abcdefghijiklmdef&quot;, &quot;def&quot;, $answer1 + 3);

print(&quot;index() def is at $answer1 and next at $answer2\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="intEXPR">

int ([EXPR])</A></H3>

<P>

<B>Category:</B> Math<BR>

<B>Return Value:</B> SCALAR, the integer portion of <TT>EXPR</TT>.

<BR>

<B>Definition:</B> Chops of any fractional part of <TT>EXPR</TT>

or <TT>$_</TT> if no expression is

specified.<BR>

For example, <TT>int(21.45)</TT> would

return <TT>21</TT>.

<BLOCKQUOTE>

<PRE>

print(&quot;int() &quot;, int(345.678), &quot;\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="ioctlFILEHANDLEFUNCTIONSCALAR">

ioctl (FILEHANDLE, FUNCTION, SCALAR)</A></H3>

<P>

<B>Category:</B> File, UNIX<BR>

<B>Return Value:</B> SCALAR, true if successful; false if not

and the undefined value in some cases.<BR>

<B>Definition:</B> Controls Input/Output operations, mainly used

for terminals. It calls the UNIX <TT>ioctl()</TT>

fuNCtion with the specified parameters. Returns undefined if the

operating system returns -1. Returns string &quot;0 but true&quot;

if the operating system returns 0. Otherwise returns the value

returned by the operating system. You can find more information

about <TT>ioctl()</TT> in section

2 of the UNIX manual pages.

<H3><A NAME="joinEXPRLIST">

join (EXPR, LIST)</A></H3>

<P>

<B>Category:</B> Array, String<BR>

<B>Return Value:</B> SCALAR, a string with each element of <TT>LIST</TT>

alternating with <TT>EXPR</TT>.<BR>

<B>Definition:</B> CoNCatenates all of the elements of <TT>LIST</TT>

together with <TT>EXPR</TT> as the

glue. For example, <TT>join('!', ('QQ', 'AA'))</TT>

will return <TT>'QQ!AA'</TT>.

<BLOCKQUOTE>

<PRE>

@listone = (0, 1, 2, 3);

print(&quot;join() &quot;, join(&quot;-&quot;,@listone), &quot;\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="keysHASH">

keys (HASH)</A></H3>

<P>

<B>Category:</B> Array, Hash <BR>

<B>Return Value: </B>in Scalar Context: The number of keys and,

therefore, the number of entries in <TT>HASH</TT>.

<BR>

<B>Return Value in Array Context:</B> All of the keys to <TT>HASH</TT>

in no particular order.<BR>

<B>Definition:</B> Gets a list of all keys in <TT>HASH</TT>.

The returned list is ordered by the internal storage requirements,

so it is often useful to use the <TT>sort()</TT>

fuNCtion before processing. For example, <TT>sort(keys(%hash))</TT>.

<BLOCKQUOTE>

<PRE>

%hash = ('One' =&gt; 1, 'Two' =&gt; 2, 'Three' =&gt; 3, 'Four' =&gt; 4);

print(&quot;keys() &quot;, join(&quot;-&quot;, keys(%hash)), &quot;\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="killSIGNALLIST">

kill (SIGNAL, LIST)</A></H3>

<P>

<B>Category:</B> Process<BR>

<B>Return Value:</B> SCALAR, the number of processes successfully

signaled.<BR>

<B>Definition:</B> Sends <TT>SIGNAL</TT>

to the processes identified by <TT>LIST</TT>.

If <TT>SIGNAL</TT> is negative then

process groups are killed instead.

<H3><A NAME="lcEXPR">

lc (EXPR)</A></H3>

<P>

<B>Category:</B> String<BR>

<B>Return Value:</B> SCALAR, a copy of <TT>EXPR</TT>

with all letters in lowercase.<BR>

<B>Definition:</B> Creates a copy of <TT>EXPR</TT>

with all letters in lowercase.

<BLOCKQUOTE>

<PRE>

print(&quot;lc() &quot;, lc(&quot;ABCDef&quot;), &quot;\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="lcfirstEXPR">

lcfirst (EXPR)</A></H3>

<P>

<B>Category:</B> String<BR>

<B>Return Value:</B> SCALAR, a copy of <TT>EXPR</TT>

with the first letter in lowercase.<BR>

<B>Definition:</B> Creates a copy of <TT>EXPR</TT>

with the first letter in lowercase.

<BLOCKQUOTE>

<PRE>

print(&quot;lcfirst() &quot;, lcfirst(&quot;ABCDef&quot;), &quot;\n&quot;);

</PRE>

</BLOCKQUOTE>

<H3><A NAME="lengthE