perl pattern matching

[Niko]

Hi,

i need help replacing string in the middle of line like this :


var1:string:yyy:zzz:kkk.....:ggg


Need to replace the string.

I already know the value of var1, that help me to find the specific line in my file.

only left is to replace the string with a new string.

any idea ?

Thanks.

 

[Paul Lalli]

Hi,

i need help replacing string in the middle of line like this :

var1:string:yyy:zzz:kkk.....:ggg

Need to replace the string.

I already know the value of var1, that help me to find the specific line in my file.

only left is to replace the string with a new string.

any idea ?

Your problem statement is much too vague. Where is the string you want
to replace stored? (ie, in what variable?). With what do you want to
replace this string? Do you want to replace *all* of the string, or
just a part of it?

Whenever possible, post a *short* but *complete* program that
demonstrates the problem you need to solve. That means actual, real
Perl code that other people can copy and run.

Paul Lalli

 

[Peter Hickman]

Hi,

i need help replacing string in the middle of line like this :


var1:string:yyy:zzz:kkk.....:ggg


Need to replace the string.

I already know the value of var1, that help me to find the specific line in my file.

only left is to replace the string with a new string.

any idea ?

Thanks.

Well this works but it assumes that : is a field delimiter and does not appear
in the data, specifically it does not appear in the first two fields.

$x = 'var1:string:yyy:zzz:kkk:ggg';
@l = split(':', $x);
$l[1] = 'fred';
$x = join(':', @l);
print "$x\n";

 

[J. Gleixner]

Hi,

i need help replacing string in the middle of line like this :


var1:string:yyy:zzz:kkk.....:ggg


Need to replace the string.

I already know the value of var1, that help me to find the specific line in my file.

only left is to replace the string with a new string.

any idea ?

Thanks.

I'm guessing you want to replace 'string', in your example line above,
with another value and you know the beginning of the line you want to
replace, which in this case is 'var1'.

my $str = 'var1:string:abcd:edfg';
my $beg = 'var1';
my $new_string = 'new_value1';

$str =~ s/^$beg[^:]*)/$beg:$new_string/;

print $str, "\n";

In the future, it'd really help others if there was code or a few lines
of data, showing cases where you want the line changed and where you
don't want them changed. That would help find a more accurate solution.

See ya

 

[Niko]

Hi again,

First thanks a lot.
and next time i will put up some line codes to make things much more clear.

for now this was my code :

### Find and replace strings in a file
sub Find_Rep {
my $PAT_TXT = $_[0];
open (FILE,$S_FILE);
open (TEMPF,"> $T_FILE");
while (<FILE>) {
eval $PAT_TXT;
print TEMPF $_;
<STDIN>;
}
close (TEMPF);
close (FILE);

####
$S_FILE="source file";
$T_FILE="target file";
$str1="var1";
str2="var2";

my $PAT_ST = 's/^$str1[^:]*)/$str1:$str2/';
Find_Rep($PAT_ST);


Thanks again.

Nissim

Hi,

i need help replacing string in the middle of line like this :


var1:string:yyy:zzz:kkk.....:ggg


Need to replace the string.

I already know the value of var1, that help me to find the specific line in my file.

only left is to replace the string with a new string.

any idea ?

Thanks.

I'm guessing you want to replace 'string', in your example line above,
with another value and you know the beginning of the line you want to
replace, which in this case is 'var1'.

my $str = 'var1:string:abcd:edfg';
my $beg = 'var1';
my $new_string = 'new_value1';

$str =~ s/^$beg[^:]*)/$beg:$new_string/;

print $str, "\n";

In the future, it'd really help others if there was code or a few lines
of data, showing cases where you want the line changed and where you
don't want them changed. That would help find a more accurate solution.

See ya

 

[Brian McCauley]

Niko top-posts:

[ please don't top-post ]

"J. Gleixner" <[email protected]> wrote in message

i need help replacing string in the middle of line like this :

var1:string:yyy:zzz:kkk.....:ggg

I'm guessing you want to replace 'string', in your example line above,
with another value and you know the beginning of the line you want to
replace, which in this case is 'var1'.

my $str = 'var1:string:abcd:edfg';
my $beg = 'var1';
my $new_string = 'new_value1';

$str =~ s/^$beg[^:]*)/$beg:$new_string/;

for now this was my code :

### Find and replace strings in a file
sub Find_Rep {
my $PAT_TXT = $_[0];

It is more ideomatic (and faster) to say:

my $PAT_TXT = shift;

or

my ($PAT_TXT) = @_;

open (FILE,$S_FILE);
open (TEMPF,"> $T_FILE");

You should always, yes always, check the return value from open(). In
quick-and-dirty program it is sufficient to append "or die $!".

You should generally avoid using shared variables to pass arguments to
subrouitnes unless there is a special reason why it's justified.

If you use a bare file handle, FILE, in a subroutine you should use
local(*FILE). Better would be to use lexical file handles (unless you
need compatability with old Perls).

while (<FILE>) {
eval $PAT_TXT;

You should usually check the value of $@ after eval. If you can't think
of something more appropriate just re-throw with:

die $@ if $@;

But you shouldn't be using eval at all anyhow - you should be calling a
precomplied code entity - see below.

print TEMPF $_;
<STDIN>;
}
close (TEMPF);
close (FILE);

I think you have a missing closing curly.

####
$S_FILE="source file";
$T_FILE="target file";
$str1="var1";
str2="var2";

This is an error.

my $PAT_ST = 's/^$str1[^:]*)/$str1:$str2/';
Find_Rep($PAT_ST);

You should use the natural representation for things (i.e. use a CODE
entity not a string for holding code).

You should use the natural name for things (i.e. don't use 'PAT' for the
name of a variable containing a substition command).

The capture brackets are redunant.

It would be a good idea to habitually put tThe $str1 on the LHS of the
s/// in \Q\E just in case it ever contains RE-special punctuation.

It would be more conventional to preserve the unchanged bit using a
capture rather the repeat it on each side of the s///.

my $substitution = sub { s/^(\Q$str1\E[^:]*/$1$str2/ };