G'day semipro,

Welcome to the monastery.

Please add <code>...</code> tags around your posted code: it's very hard to read as is.

You problem is probably this line:

my $S="C:Users\name\Desktop\a.txt";
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Characters prefixed with a backslash inside double-quotes have a special meaning. See perlop: Quote and Quote-like Operators and perlop: Quote-Like Operators.

You can fix this by either doubling up the backslashes:

my $S="C:Users\\name\\Desktop\\a.txt";
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or simply using single-quotes instead:

my $S='C:Users\name\Desktop\a.txt';
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I don't use MSWin much, but I think you have an additional problem with C:Users: should that be C:\Users?

You should use warnings; Because the default for filehandle is *input*. So when you write open(FILE, "$S") you open the file for reading. You should have been warned about that.

@lines = <FILE> makes a copy of the file content, but for(@lines) doesn't make any copy, inside the for loop $_ is not a copy of a line, it's the line itself. So in the end @lines and @newlines are certainly the same.

Hi, thnx! i put the warnings on. While xecuting the cmd interface tells me if he can not find a file. But he can, so the a.txt file adress should be ok. bīBut there is still no effect and no warnings. Your comment on the @ lines sounds convenient, so finally he is copying the old line in the new line and nothing is happening? How can I fix that issue? And here (sorry not the original but the same principle)the code (which has no effect):

    #!/usr/bin/perl -w      

  

use strict;


my $SCU='C:/Users/name/Desktop/a.txt';


open(FILE, "<$SCU") || die "File not found";

my @lines = <FILE>;

close(FILE);


my @newlines;

foreach(@lines) {
 
  $_ =~ s/<ABCD>/xyz/g;
 
  push(@newlines,$_);
}


open(FILE, "$SCU") || die "File not found";

print FILE @newlines;

close(FILE);
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You should edit your first post instead of posting your code again. The editing area should appear just below your original post.

About your posted-again code, there's still no > in your second open, so you can't write on the file. Write open (FILE, ">", "$SCU") or die "Could not open file $SCU: $!";. $! is a special var that contains the error that occurred while trying to open your file.

If you do not want to modify the output of @lines in your for loop, you can either make an explicit copy with my $copy = $_; or, if you use a recent version of Perl, use the /r switch on the substitution, which means that the result is returned, and the original variable is not affected. If you do not write $var =~ s/pattern/replace/; but just s/pattern/replace; it works on $_ by default BTW. So in your case you could write (if you get an error, your version of Perl is probably too old):  push @newlines, s/<ABCD>/xyz/rg for @lines;

Another possible approach is a Perl one-liner at the DOS command line:

Try it with unimportant test files first. The replacements will occur in the existing file, and the old contents should be saved to a .bak file.

Hi, thnx. Yeah thats working!!! cool

Hi, ok I was bit early ecouraged. the line  perl -pi.bak -e "s/test/replace/g;" filename.txt works as DOS command. But when I try to squeez it in my skript he needs an operator before the file path. So

 
#!/usr/bin/perl -w
perl -pi.bak -e "s/test/replace/g;" C:/user/Desktop/filename.txt
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is not working. Can you help me out, again? Thank you!

Yeah, on the DOS or UNIX command line, the "-pi.bak -e" options have the effect of considerably simplifying the syntax for modifying a text file.

If you want to write a real script, it is slightly more complicated, those simplifications no longer apply.

Within a Perl script, you would need to do something like this;

#!/usr/bin/perl;
use strict;
use warnings;

my $file_in = shift;
open my $FH, "<", $file_in or die "cannot open $file_in $!";
while (<$FH>) {
     s/test/replace/g;
     print;
}
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The above might still be considered simplistic, it is just giving an idea. Please don't hesitate to ask if you need further information.

Just tried to replace a string called "test" by "replace" in a txt file

  $_ =~ s/test/replace/g;
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If that doesn't work, try tips from the Basic debugging checklist: print and Data::Dumper.

Please edit your post and add code tags around your code: Writeup Formatting Tips