swaping words

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to write a code that first asks the user for a file name. If the imput name exists, the user is then asked for a word, word_1, which already exists in the given file. Then the user is asked for a second word, word_2, which is to replace word_1. Everything seems to be working fine except that word_2 is just added to the file in stead of taking the place of word_1. What am I doing wrong?

Here's the code:

#!/usr/bin/perl -w

print "Please Enter the Name of a File: ";
$file = <STDIN>;

if (open(HANDLE, "$file")) {
print "Please Enter a word from $file: ";
$word_1 = <STDIN>;
print "Please Enter a Word to Replace, $word_1, with: ";
$word_2 = <STDIN>;}

@x=<HANDLE>;
open (HANDLE, "$file");
open (HANDLE, ">>$file");
foreach $variable (@x) {
if ($word_1=~/$variable/i) {
$variable = $word_2;
print @x;}}
[download]

Thanks, Sam

Comment on swaping words Download Code

Replies are listed 'Best First'.
Re: swaping words by VSarkiss (Monsignor) on Feb 11, 2002 at 00:12 UTC
The first problem is that your `$word_1` has a newline at the end. Since this is almost surely not what you want to do, you should `chomp` both words after you read them in. As BazB has pointed out above, you're opening and closing the file several times unnecessarily. Also, if your `open` fails, there's not much clue about what's happening. It's much clearer to check for errors when opening, then `close` the handle explicitly, then open it for writing (since you'll be re-writing its contents). Finally, if you're going to read in the whole file and do match-and-substitute, it's a lot easier not to use an array. Just read the whole thing into a scalar, and do a global replace. Put it all together, and it looks like this: open HANDLE, $file or die "Couldn't open $file: $!\n"; print "Please Enter a word from $file: "; chomp($word_1 = <STDIN>); print "Please Enter a Word to Replace, $word_1, with: "; chomp($word_2 = <STDIN>); # Read the whole thing in. undef $/; $x = <HANDLE>; close HANDLE; # Re-open for writing, clobbering the file. open HANDLE, ">$file"; # Change every instance $x =~ s/$word_1/$word_2/g; # To prevent changing substrings, it would almost # certainly be better to use: # $x =~ s/\b$word_1\b/$word_2/g; # But it's your call.... print HANDLE $x; [download] At this point, I should probably also chide you for not using strict and warnings, but I'll let you off easy this time. ;-) HTH	[reply] [d/l] [select]
Re: swaping words by BazB (Priest) on Feb 10, 2002 at 23:56 UTC
`open (HANDLE, "$file"); open (HANDLE, ">>$file");` [download] I'd think you only need to open the filehandle once. The second `open()` statement is opening $file for appending only, which can't be useful in this case. Why not use `s/$word_1/$word_2/i` or similar?	[reply] [d/l] [select]