No, I don't mind at all. Shame on me for throwing up code without explaining it :o
Code:
open (IN, "file") or die "Can't read file: $!\n"; # 1
while ( <IN>) { # 2
chomp; # 3
my @fields = split; # 4
if ($fields[0] =~ /PATTERN/) { # 5
# do something
}
}
close(IN); # 6 # 1 - Here I'm using the "open" function to attach the file handle IN to the external file "file". If it's unsuccessful, the script dies and gives an error message.
# 2 - I'm using the diamond operator (<>) with the file handle to read each line in the file. Used with "while" it means, "execute this block as long as there is a line to be read from IN". Each line gets set to the variable $_ in turn.
# 3 - Remove any trailing newline.
# 4 - Each line gets split up into a list (split uses the pattern /\s+/ to split by default). I regularly use files with tab-delimited fields, so this is convenient for me.
# 5 - This says, "execute this block if the first item in the list looks like this pattern".
# 6 - This just explicitly closes the file I was looking in.
Code:
my @lines = <IN>; # 1
my @stuff = grep { /PATTERN/ } @lines; # 2
print @stuff; # 3 You could use these lines in place of the while loop, if you wanted a list of entire lines for which a given expression is true (usually a pattern match).
# 1 - Read all lines from IN into a list, where the first element is the first line, and so on.
# 2 - This says, "if an element in the list @lines contains PATTERN, add it to the list @stuff". It's just quicker than writing a for loop with a conditional and all that.
# 3 - This just spits out whatever is in @stuff. Notice that the input wasn't chomped, and that the @stuff isn't surrounded with quotes. I'm assuming that the input file has one record on each line, and I don't want the print function to put extra spaces between the list elements.
I know there are some file access tutorials online, but I've found that they're generally limited in scope and can't compete with a good book at hand. Oh, and
coderforums.net is another good forum to visit. There are plenty of people there that know a ton more about Perl than me
