Hi,
Thanks alot for the detailed explanation.
Regards
Anand Kumar
Prabu <[EMAIL PROTECTED]> wrote:
anand kumar wrote:
> hi all,
>
> I could not understand clearly the functions
> qw(),qq(),qr(),qx(),q(),quotemeta(). I
> have read the explanation for these functions in the perl documentation but i
> could not get idea of where exactly we can use these functions. So please
> send some other links or examples for these functions.
>
> Thanks in advance for the help
>
> Regards
> Anand Kumar
Hello Anand,
q/STRING/
STRING
A single-quoted, literal string.A generalized single-quote operation.
A backslash represents a backslash unless followed by the delimiter or
another backslash, in which case the delimiter or backslash is interpolated.
for example
$foo = q!Hello World!; This is equivalent to $foo='hello world';
_________________________________________________________________________________
qq/STRING/
"STRING"
A double-quoted, interpolated string.
for example
$foo = qq!Hello World!; This is equivalent to $foo='hello world';
_________________________________________________________________________________
qr/STRING/imosx
This operator quotes (and possibly compiles) its STRING as a regular
expression. STRING is interpolated the same way as PATTERN in "m/PATTERN/"
Options are:
i Do case-insensitive pattern matching.
m Treat string as multiple lines.
o Compile pattern only once.
s Treat string as single line.
x Use extended regular expressions.
For example
$rex = qr/my.STRING/is;
s/$rex/foo/;
This is equivalent too
s/my.STRING/foo/is;
_________________________________________________________________________________
qx/STRING/
STRING
A string which is (possibly) interpolated and then executed as a system
command with "/bin/sh" or its equivalent. Shell wildcards, pipes, and
redirections will be honored. The collected standard output of the
command is returned; standard error is unaffected.
qx(ls); This is equivalent to `ls` (backtics)
qw/STRING/
Evaluates to a list of the words extracted out of STRING, using embedded
whitespace as the word delimiters.
@a=qw(foo bar baz); This is equivalent too @a=("foo", "bar", "baz");
_________________________________________________________________________________
quotemeta EXPR
Returns the value of EXPR with all non-"word" characters backslashed.
_________________________________________________________________________________
A Small Example
PROGRAM
$ cat func.pl
#!/usr/bin/perl
$foo = q!Hello World\n!;
print "single-quote operation\n\t",$foo."\n";
$foo = qq!Hello World\n!;
print "double-quote operation\n\t",$foo;
$foo = "Hello world";
$pattern = qr!Hello!is;
$foo=~s/$pattern/HELL0/;
print "Regex operation\n\t",$foo;
@a=qw(hello perl world);
print "\nTurn a space-delimited string of words into a list\n\t";
foreach(@a){
print "$_\n\t";
}
$foo="Hello*world";
$non_word_char = quotemeta($foo);
print "\nBackslashed non-word characters\n\t",$non_word_char."\n";
print qx/ps/;
OUTPUT
$ perl func.pl
single-quote operation
Hello World\n
double-quote operation
Hello World
Regex operation
HELL0 world
Turn a space-delimited string of words into a list
hello
perl
world
Backslashed non-word characters
Hello\*world
PID TTY TIME CMD
20453 pts/5 00:00:00 bash
20737 pts/5 00:00:00 perl
20738 pts/5 00:00:00 ps
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