String substitution

kirk123 has asked for the wisdom of the Perl Monks concerning the following question:

I use the following code to open a text file and update any strings such as "apple" to orange".

open (IN,"c:\\data");
          @lines = <IN>;
          close IN;
        
@lines = map { s/\b$old_hostname\b/$new_hostname/sgi; $_ } @lines;
          open (OUT,">c:\\data") || "can't open data :$! ";
          print OUT @lines;
[download]

But now I must change any words that that have "apple" as a substring to any words that have "orange" as a substring. For example "data/applered" or "new_apple_dark" becomes " data/orangered" "new_orange_dark" and so on .

How can I alter my substitution to make it work.

--thanks kirk

Comment on String substitution Download Code

Replies are listed 'Best First'.
Re: String substitution by Paladin (Vicar) on Apr 17, 2003 at 19:16 UTC
If you don't want to match against word boundries `\b`, then remove those constraints from the regex. ie. `s/$old_hostname/$new_hostname/sgi` [download] Note: You may also want to add `\Q` and `\E` around your `$old_hostname` if you don't want any special regex characters in there to affect the match. `s/\Q$old_hostname\E/$new_hostname/sgi` [download]	[reply] [d/l] [select]
Re: String substitution by thelenm (Vicar) on Apr 17, 2003 at 19:24 UTC
If I understand correctly, you can probably achieve your desired output by removing the `\b` elements in your substitution. `\b` only matches at a word boundary, and it sounds like you don't want that. Also, a couple notes on your code... `$_` is aliased to each element of your array when using `map` or a for loop, so there's no need to do something like `@lines = map { s/...//; $_ } @lines;` ... You can just say `s/...// for @lines;` If you're reading and writing to the same file, you can use the -i option on the command line. So you could probably shorten your entire code to this: `perl -pi.bak -e 's/apple/orange/gi' c:\data` [download] This will overwrite your original file, substituting 'apple' with 'orange' wherever it is found, and will make a backup copy with a .bak extension in case that's not what you wanted. -- Mike `-- just,my${.02}`	[reply] [d/l] [select]
Re^2: String substitution by Anonymous Monk on Aug 09, 2006 at 19:59 UTC
Is there a way to use: perl -pi.bak -e 's/apple/orange/gi' c:\data w/o the '-pi.bak' part; without making a backup of the file	[reply]
Re^3: String substitution by ikegami (Patriarch) on Aug 09, 2006 at 20:36 UTC
The `p` and the `i` are seperate options. You definitely want to keep the `p`, and you definitely want to keep the `i` ("inplace"), but if you don't specify an extention, the backup file isn't created. This is all documented in perlrun. `perl -pi -e 's/apple/orange/gi'` [download] Caveat: `i` without an extention does not work in Windows.	[reply] [d/l] [select]
Re^2: String substitution by Anonymous Monk on Aug 11, 2006 at 17:23 UTC
Is there a way to use: perl -pi.bak -e 's/apple/orange/gi' c:\data w/o the '-pi.bak' part	[reply]
Re: String substitution by dpuu (Chaplain) on Apr 17, 2003 at 19:18 UTC
You need to remove the `\b`s. (as an aside: you can also replace `map` with `foreach`): `foreach (@lines) { s/apple/orange/g }` [download] --Dave	[reply] [d/l] [select]