One-liner for Matching a Regex in a Directory of Files

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

I have a directory with about thirty text files. I was trying to find an acronym in the directory, but I didn't really remember what it was (other than it was a four letter word starting with M).

I tried a few one-liners, but none of them worked. Since I was just trying to find something really quickly, I decided to punt and just write a script to do what I wanted.

Now I'm trying to learn more about one-liners (I don't have any experience with them) just so I can handle this situation a bit better next time it comes up.

I should also note that I'm doing this from a Windows command prompt.

Here are some of the one-liners that I tried (in a for loop, single file example shown here):

perl -pe "m/M[A-Z]{3} /" 1-01.txt
Outputs the source file exactly.
perl -pe "if (m/(M[A-Z]{3}) /) { print $1; }" 1-01.txt
Outputs the source file exactly.

And finally, here's the subroutine that actally did what I wanted:

my @files = <*.txt>;
undef $/;
foreach (@files) {
   open ( FH, $_ );
   my $txt = <FH>;
   close ( FH );
   while ( $txt =~ m/(M[A-Z]{3}) /gs ) { print "  $1\n"; }
}
[download]

Is there a way to do something like this as a one-liner? If so, then can I incorporate the glob into the one-liner? Thanks for your help.

_{janitored by ybiC: Prepend tile wit "One-liner" for searchability}

Comment on One-liner for Matching a Regex in a Directory of Files Select or Download Code

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Re: One-liner for Matching a Regex in a Directory of Files by Paladin (Vicar) on Jan 10, 2004 at 20:18 UTC
You were close with your second one-liner. From perldoc perlrun you'll notice that `-p` wraps your code in: LINE: while (<>) { ... # your program goes here } continue { print or die "-p destination: $!\n"; } which prints everyline by default, while `-n` wraps your code in: LINE: while (<>) { ... # your program goes here } Note, there is no automatic printing here. So if you use `-n` instead of `-p` in your second one-liner, you would have what you want.	[reply] [d/l] [select]
Re: One-liner for Matching a Regex in a Directory of Files by allolex (Curate) on Jan 10, 2004 at 20:56 UTC
a four letter word starting with M In that case, you should also be using the carat to tell your regex that the letter "M" is found just after the beginning of the filename. `m/^M[A-Z]{3}/` [download] So you get: `perl -le'foreach ( <*.txt> ) { print if /^M[A-Z]{3}/ }'` [download] -- Allolex	[reply] [d/l] [select]
Re: (2) One-liner for Matching a Regex in a Directory of Files by svsingh (Priest) on Jan 11, 2004 at 02:15 UTC
Sorry, I didn't mean to imply that that M was at the beginning of the file. Each text file is a separate essay and the acronym was just a word in the body of the file. I combined ideas from both tips to come up with the following (semi-Perl) solution. Thanks for your help Paladin and allolex. `for %a in (*.txt) do @perl -ne "if (m/ (M[A-Z]{3}) /) { print qq($1\n); }"` `%a`	[reply] [d/l] [select]
Re: One-liner for Matching a Regex in a Directory of Files by davido (Cardinal) on Jan 11, 2004 at 06:00 UTC
I happen to like the following one liner because its output is the entire line that matches, which provides context. `perl -ne "print qq/$. : $_\n/ if m/\bM[A-Z]{3}\b/" testfile.txt` [download] In that one liner, any line that contains a four letter capitalized word starting with M, the whole line will print, so you can get a good idea of where it appears in the file. Also, the line number within the file is printed for added clarity. The regex uses the `\b` "word boundry" assertion at both sides of the `M[A-Z]{3}` construct, to ensure that four and only four letters will trigger a match. Dave	[reply] [d/l] [select]

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