(a) $_ represents the current line of file f3 that is being processed by the Perl one-liner.
(b)
In regular expression terminology, "\b" is a word boundary. It doesn't represent a character in a string, but a condition at a certain position. It's a zero-width assertion.
(c)
The regular expression "\babc\b" means - a word boundary, followed by literal characters "a", "b", "c", followed by another word boundary. In effect, it matches the word "abc".
(d) // is Perl's pattern match operator. So, /\babc\b/ means the word "abc" is searched. Searched where ? Searched in the current line $_. If it is not mentioned, Perl assumes that the current line is to be searched.
All the following forms are equivalent:
which can be seen here:
(e)
"?:" is the ternary operator that Perl borrowed from C. It works like an "if-then-else" - if the argument before the ? is true, the argument before the : is returned, otherwise the argument after the : is returned.
So in this one-liner, if /\babc\b/ is true, then "$_.txt" is returned i.e. the current line followed by ".txt" is returned.
If /\babc\b/ is false, then $_ is returned i.e. the current line is returned as it is.
(f)
The "print" function prints the value returned at (e) to the standard output.
So, essentially the Perl one-liner searches for the word "abc" in the current line of file f3. If found, it prints current line followed by ".txt". Otherwise, it simply prints the current line.
It does this for all lines of file f3 due to the "n" command-line option (the "n" in -lne).
The one-liner could be written in a verbose manner thusly -
In fact, you could be more verbose and write a Perl program that uses the "open" and "close" functions and while loop to open, process and close the file.
HTH,
tyler_durden
This User Gave Thanks to durden_tyler For This Post:
I have lines in a file that look like this:
machine: machinea
machine: machineb
machine: randomwhatevermachine
I want to replace the machine lines with:
machine: machinec
I tried
perl -pi -e "s/#machine:\?*/machine: machinec/" filename
But this ended up doing this:
... (2 Replies)
I've been working on this all night and finally have to ask for help... and not just from my coffee pot.
I need to replace a line of text only when it is proceeded by a line containing only the letter "H"
Input:
H -2.204711 -0.922090 -0.024814
P
6-311+G(d)
****
C
6-311+G(d)... (7 Replies)
Hi friends,
I want to substitute "a ='....'," with ":" in everywhere in a string using Perl.
Details:
----------
my $str= " c1='fgfasfgasggfgff.,akhkhahha', c2='bbbn', c3='hg5 sh' ";
Required o/p: $str= " c1:c2:c3 "
I tried as below:
$str=~ s/=\'.*\',/:/g ;
print "str=... (14 Replies)
Hi,
I have a template file and want to replace 3 parameters to the values that I want. these values are in a parameter file.
Any idea how to do this in perl?
the parameter file looks like:
host_name = jupiter
PORT = 1562
IPADDRESS = 10.1.34.10
the template file has lots of entry.... (1 Reply)
Hello all
I have a strings like
" Watch news 24x7 "."x-wars is glowing"
" Watch news like 24 x 7"."x-mas will be celebrated"
" Dimensions of box is 24x23x47 ".
I have to remove the x(by) in between the number. If i just replace x, it will also remove all x's from text which i do not want.... (1 Reply)
I have a large text csv file that I'm working with. It will look something like this:
D,",E",C
O,"F,",I
O,gh,R
The second column always has a two digit random code (can be numbers, letters or any characters). When one of the characters happens to be a comma, the string is quoted. I want to... (5 Replies)
Hi,
I'm new to Perl, and I want to change a few columns in a file in order to insert them into a database.
The input file looks like this:
00001,"01/1234567" ,"Tst2"
00002,"01/4545646" ,"Tst123456"
00003,"01/8979898" ,""
The output should look like this:
01-1234567,00001... (2 Replies)
hi Geeks,
my input file contains data like =>
53 - Deewana Kar Raha Hai.mp3
54 - Hale Dil.mp3
55 - Ishq Sufiyana.mp3
56 - Abhi Kuch Dino Se.mp3
57 - Pee Loon Hoto Ki Sargam.mp3
I had used sed command to remove the prefix from the file name like
sed 's/^\
it gives me the perfect... (4 Replies)
Hi,
With the following Perl syntax, how to print the $_ value after the substitution?
s/(\s*|\n)//g foreach (<>);
If I use the below code, it produces some numeric output print s/(\s*|\n)//g foreach (<>); (2 Replies)
OSX
I have been grinding my teeth on a portion of code. I am building a bash script that edits a html email template. In the template, I have place holders for SED (or whatever program is appropriate) to use as anchors for find and replace, with user defined corresponding html code. The HTML code... (3 Replies)