search substring in a large string

[Paul]

hi, greetings,

I want to get the substring with the same prefix in a large string
(about 6K size ). like this,


$mystring="adfadfabcdefg234q34qwerqwerqewrqwerqwerabcdefgh12345dafsdfe4q35345abcdefghhherwrtwert3245234";

$pos1=index($mystring,"abcdefgh");

$substring=substr($mystring,$pos1,16);


In this way, I can get the first 16bit substring after "abcdefgh", the
questions is How can I get the 2nd, 3rd substring after "abcdefgh"?


thanks.

 

[Jürgen Exner]

I want to get the substring with the same prefix in a large string
(about 6K size ). like this,


$mystring="adfadfabcdefg234q34qwerqwerqewrqwerqwerabcdefgh12345dafsdfe4q35345abcdefghhherwrtwert3245234";

$pos1=index($mystring,"abcdefgh");

$substring=substr($mystring,$pos1,16);


In this way, I can get the first 16bit substring

What is a 16bit substring?

after "abcdefgh", the
questions is How can I get the 2nd, 3rd substring after "abcdefgh"?

Just an idea: why not split() the string at 'abcdefgh' an then grab whatever
you need from each element of the returned list?

jue

 

[Gunnar Hjalmarsson]

I want to get the substring with the same prefix in a large string
(about 6K size ). like this,

$mystring="adfadfabcdefg234q34qwerqwerqewrqwerqwerabcdefgh12345dafsdfe4q35345abcdefghhherwrtwert3245234";

$pos1=index($mystring,"abcdefgh");

$substring=substr($mystring,$pos1,16);

In this way, I can get the first 16bit substring after "abcdefgh",

Suppose you mean the first 16 characters substring beginning with
"abcdefgh".

How can I get the 2nd, 3rd substring after "abcdefgh"?

my ($pos, @substrings) = 0;
while ( ( $pos = index $mystring, 'abcdefgh', $pos ) >= 0 ) {
push @substrings, substr($mystring, $pos, 16);
$pos += 16;
}

 

[Anno Siegel]

hi, greetings,

I want to get the substring with the same prefix in a large string
(about 6K size ). like this,


$mystring="adfadfabcdefg234q34qwerqwerqewrqwerqwerabcdefgh12345 dafsdfe4q35345abcdefghhherwrtwert3245234";

$pos1=index($mystring,"abcdefgh");

$substring=substr($mystring,$pos1,16);


In this way, I can get the first 16bit substring after "abcdefgh", the

You mean "16-byte substring".

questions is How can I get the 2nd, 3rd substring after "abcdefgh"?

Read the documentation of index again and pay attention to the parameter
named "POSITION".

Or get them all at once:

my @extract = $mystring =~ /abcdefgh(.{16})/sg;

Anno

 

[Brian McCauley]

You mean "16-byte substring".

You mean "16-character substring"

substr() operates on characters not bytes unless the "use bytes" pragma
is in effect.

 

[Brian McCauley]

hi, greetings,

I want to get the substring with the same prefix in a large string
(about 6K size ). like this,
$mystring="adfadfabcdefg234q34qwerqwerqewrqwerqwerabcdefgh12345dafsdfe4q35345abcdefghhherwrtwert3245234";

$pos1=index($mystring,"abcdefgh");

$substring=substr($mystring,$pos1,16);

In this way, I can get the first 16bit substring after "abcdefgh", the
questions is How can I get the 2nd, 3rd substring after "abcdefgh"?

Although index()/substr() are often faster at runtime it may be more
ideomatic to use a regex match.

If you perfer to optomise for readability over speed and want to loop
through all matches...

while ( $mystring =~ /(abcdefgh.{8})/g ) {
my $substring = $1;

}