Chopping strings
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 How should I do to split a long string that the only thing I know is that is a multiple of a previous defined number (for example 26). A graphic example: abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz That's four times 26 (104) but I don't (I can't) count every string because they are really long (They can be of thousands of charachters). So what I should do, I think, is a loop that get the first 26 charachters and print them in a new file, after that evaluates if there is more string to get, and so on, but I am not able to see how it works... :-/ Give me some advice, please (the command I should use, or group of commands, etc...) Thanks in advance for your help and patience. Josep Sànchez ~ [papapep] -BEGIN PGP SIGNATURE- Version: GnuPG v1.2.1 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQE+U2pP2vx52x0kyz4RArgbAKCwR88CWEfO0I8eePfRL42XsoTKxACgkm5d hJTlHvX22x+LSCazIBDsruc= =qw3e -END PGP SIGNATURE- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Chopping strings
From: papapep [EMAIL PROTECTED]
How should I do to split a long string that the only thing I know is
that is a multiple of a previous defined number (for example 26).
A graphic example:
abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqr
stuvwxyzabcdefghijklmnopqrstuvwxyz
That's four times 26 (104) but I don't (I can't) count every string
because they are really long (They can be of thousands of
charachters).
So what I should do, I think, is a loop that get the first 26
charachters and print them in a new file, after that evaluates if
there is more string to get, and so on, but I am not able to see how
it works... :-/
while ($long_string ne '') {
my $chunk = substr( $long_string, 0, 26);
substr( $long_string, 0, 26) = '';
# yes I know this looks strange. Forget Computer Science, it does
# what it looks like doing.
...
}
Jenda
= [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =
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Re: Chopping strings
Papapep wrote:
How should I do to split a long string that the only thing I know is
that is a multiple of a previous defined number (for example 26).
A graphic example:
abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz
That's four times 26 (104) but I don't (I can't) count every string
because they are really long (They can be of thousands of charachters).
So what I should do, I think, is a loop that get the first 26
charachters and print them in a new file, after that evaluates if there
is more string to get, and so on, but I am not able to see how it
works... :-/
Give me some advice, please (the command I should use, or group of
commands, etc...)
Here are a couple of ways to do it:
my $length = 26;
my $string = 'abcdefghijklmnopqrstuvwxyz' x 4;
Split on arbitrary length using match operator:
for my $line ( $string =~ /.{1,$length}/sg ) {
# $line contains 1 to $length characters
}
Split on arbitrary length using substr (C style):
for ( my $index = 0; my $line = substr $string, $index, $length; $index += $length ) {
# $line contains 1 to $length characters
}
John
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Re: Chopping strings
Jenda Krynicky wrote:
while ($long_string ne '') {
my $chunk = substr( $long_string, 0, 26);
substr( $long_string, 0, 26) = '';
Or just:
my $chunk = substr( $long_string, 0, 26, '' );
But that is inefficient because you modify the beginning of the string
on each iteration.
John
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RE: Chopping strings
John W. Krahn wrote:
Papapep wrote:
How should I do to split a long string that the only thing I know is
that is a multiple of a previous defined number (for example 26).
A graphic example:
abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx
yzabcdefghijklmnopqrstuvwxyz
That's four times 26 (104) but I don't (I can't) count every string
because they are really long (They can be of thousands of
charachters).
So what I should do, I think, is a loop that get the first 26
charachters and print them in a new file, after that evaluates if
there is more string to get, and so on, but I am not able to see how
it works... :-/
Give me some advice, please (the command I should use, or group of
commands, etc...)
You might look at sysopen, sysread which allows you to read in max
blocks of data and process that data.
It would look something like:
sysopen(FILEIN,$filein,0) || die unable to open file $filein: $!;
bindmode(FILEIN);
my $rcdbuf = ;
my $rcdcnt = 0;
my $rcdmax = 26;
my $rcdcntrtn = 0;
my @MyWorka = ();
while ( 1 ) {
sysseek(FILEIN,$rcdmax*$rcdcnt,0);
$rcdcntrtn = sysread(FILEIN,$rcdbuf,$rcdmax);
if ( defined $rcdcntrtn ) {
@MyWorka = unpack(a26,$rcdbuf);
$rcdcnt++;
# could write your new file out here or do what you want.
# if there can be less an x multiples, then you might need to
check the length
}else {
last ;
}
} # end of while
close(FILEIN);
A different approach. ps If there can be linefeeds or carriage returns, then
you will have to approach it different also.
Wags ;)
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Re: Chopping strings
David --- Senior Programmer Analyst --- Wgo Wagner wrote:
You might look at sysopen, sysread which allows you to read in max
blocks of data and process that data.
It would look something like:
sysopen(FILEIN,$filein,0) || die unable to open file $filein: $!;
bindmode(FILEIN);
$ perldoc -f bindmode
No documentation for perl function `bindmode' found
binmode(FILEIN);
my $rcdbuf = ;
my $rcdcnt = 0;
my $rcdmax = 26;
my $rcdcntrtn = 0;
my @MyWorka = ();
while ( 1 ) {
sysseek(FILEIN,$rcdmax*$rcdcnt,0);
Using sysseek is redundant as sysread will set the file pointer to the
end of the chunk of data it just read.
$rcdcntrtn = sysread(FILEIN,$rcdbuf,$rcdmax);
if ( defined $rcdcntrtn ) {
sysread() could return less then the requested bytes so this may not do
what you want it to do (how do you know the buffer is full?)
@MyWorka = unpack(a26,$rcdbuf);
You already (hopefully) have 26 bytes in $rcdbuf so why are you using
unpack? The 'a' format of unpack will read the data in $rcdbuf up to
the first \0 (NULL) character (like a C string) so this may not do
what you want.
$rcdcnt++;
# could write your new file out here or do what you want.
# if there can be less an x multiples, then you might need to
check the length
}else {
last ;
}
} # end of while
close(FILEIN);
A different approach. ps If there can be linefeeds or carriage returns, then
you will have to approach it different also.
John
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