local_addr = sjcapp [value2]
How do you split this string so that I get 2 values in my array i.e.
array[0] = sjcapp and array[1] = value2.
If I do this
#array = split('local_addr =', $input)
then my array[0] has sjcapp [value2]. I want to be able to separate it into two in my split function itself.
I was trying something like this but it didn't work:
split(/local_addr= \s/, $input)
Untested, but maybe something like this?
#array = ($input =~ /local_addr = (\S+)\s\[(\S+)\]/);
Rather than split, this uses a regex match in list context, which gives you an array of the parts captured in parentheses.
~/ cat data.txt
local_addr = sjcapp [value2]
other_addr = superman [value1492]
euro_addr = overseas [value0]
If the data really is as regularly structured as that , then you can just split on the whitespace. On the command line (see the perlrun(1) manual page) this is easiest with "autosplit" (-a) which magically creates an array of fields called #F from the input:
perl -lane 'print "$F[2] $F[3]" ' data.txt
sjcapp [value2]
superman [value1492]
overseas [value0]
In your script you can change the name of array, and the position of the elements within,it by shift-ing or splice-ing - possibly in a more elegant way than this - but it works:
perl -lane 'my #array = ($F[2],$F[3]) ; print "$array[0], $array[1]" ' data.txt
Or, without using autosplit, as follows :
perl -lne 'my #arr=split(" ");splice(#arr,0,2); print "$arr[0] $arr[1]"' data.txt
try :
if ( $input =~ /(=)(.+)(\[)(.+)(\])/ ) {
#array=($2,$4);
}
I would use a regexp rather than a split, since this is clearly a standard format config file line. How you construct your regexp will likely depend on the full line syntax and how flexible you want to be.
if( $input =~ /(\S+)\s*=\s*(\S+)\s*\[\s*(\S+)\s*\]/ ) {
#array = ($2,$3);
}
Related
I have a variable $string and i want to print all the lines after I find a keyword in the line (including the line with keyword)
$string=~ /apple /;
I'm using this regexp to find the key word but I do not how to print lines after this keyword.
It's not really clear where your data is coming from. Let's assume it's a string containing newlines. Let's start by splitting it into an array.
my #string = split /\n/, $string;
We can then use the flip-flop operator to decide which lines to print. I'm using \0 as a regex that is very unlikely to match any string (so, effectively, it's always false).
for (#string) {
say if /apple / .. /\0/;
}
Just keep a flag variable, set it to true when you see the string, print if the flag is true.
perl -ne 'print if $seen ||= /apple/'
If your data in scalar variable we can use several methods
Recommended method
($matching) = $string=~ /([^\n]*apple.+)/s;
print "$matching\n";
And there is another way to do it
$string=~ /[^\n]*apple.+/s;
print $&; #it will print the data which is match.
If you reading the data from file, try the following
while (<$fh>)
{
if(/apple/)
{
print <$fh>;
}
}
Or else try the following one liner
perl -ne 'print <> and exit if(/apple/);' file.txt
my #up = `cat abc.txt|head -2|tail -1|cut -d' ' -f1-3`;
Instead of storing the individual fields in the array. It's storing the entire output as a string in the first element.
This is the output I am getting
$up[0] = 'xxx 12 234'
I want this
#up = ('xxx', 12, 234)
|
It looks like you want the first three space-delimited fields of the second line of file abc.txt
The problem is that backticks will return one line of output in each element of the array, and because cut prints all three fields on a single line, they appear as a single array element.
You could split the value again inside Perl, but when you have the whole of the Perl language available, it's wasteful to use the shell to do something so simple and you should do everything in Perl
This program will do as you ask. I've used Data::Dump only so that you can verify that the contents of #up are as you wanted
use strict;
use warnings 'all';
use Data::Dump;
my #up = do {
open my $fh, '<', 'abc.txt' or die $!;
<$fh>; # Skip one line
(split ' ', <$fh>)[0 .. 2];
};
dd \#up;
output
["xxx", 12, 234]
You can either split the result by whitespaces:
my #up = split(/\s+/, `cat abc.txt ...`);
Or prior you can set input record separator to space. This one however is not as flexible, it's just simple string so in case there are two spaces in a row it will treat it as empty field in the middle:
local $/ = " ";
my #up = `cat abc.txt ...`;
I want to extract some elements from each line of a file.
Below is the line:
# 1150 Reading location 09ef38 data = 00b5eda4
I would like to extract the address 09ef38 and the data 00b5eda4 from this line.
The way I use is the simple one like below:
while($line = < INFILE >) {
if ($line =~ /\#\s*(\S+)\s*(\S+)\s*(\S+)\s*(\S+)\s*(\S+)\s*=\s*(\S+)/) {
$time = $1;
$address = $4;
$data = $6;
printf(OUTFILE "%s,%s,%s \n",$time,$address,$data);
}
}
I am wondering is there any better idea to do this ? easier and cleaner?
Thanks a lot!
TCGG
Another option is to split the string on whitespace:
my ($time, $addr, $data) = (split / +/, $line)[1, 4, 7];
You could use matching and a list on LHS, something likes this:
echo '# 1150 Reading location 09ef38 data = 00b5eda4' |
perl -ne '
$,="\n";
($time, $addr, $data) = /#\s+(\w+).*?location\s+(\w+).*?data\s*=\s*(\w+)/;
print $time, $addr, $data'
Output:
1150
09ef38
00b5eda4
In python the appropriate regex will be like:
'[0-9]+[a-zA-Z ]*([0-9]+[a-z]+[0-9]+)[a-zA-Z ]*= ([0-9a-zA-Z]+)'
But I don't know exactly how to write it in perl. You can search for it. If you need any explanation of this regexp, I can edit this post with more precise description.
I find it convenient to just split by one or more whitespaces of any kind, using \s+. This way you won't have any problems if the input string has any tab characters in it instead of spaces.
while($line = <INFILE>)
{
my ($time, $addr, $data) = (split /\s+/, $line)[1, 4, 7];
}
When splitting by ANY kind of whitespace it's important to note that it'll also split by the newline at the end, so you'll get an empty element at the end of the return. But in most cases, unless you care about the total amount of elements returned, there's no need to care.
I would like to write a script which can return me the result whenever the regex meet.I have some difficulties in writing the regex i guess.
Content of My input file is as below:
Number a123;
Number b456789 vit;
alphabet fty;
I wish that it will return me the result of a123 and b456789, which is the string after "Number " and before ("\s" or ";").
I have tried with below cmd line:
my #result=grep /Number/,#input_file;
print "#results\n";
The result i obtained is shown below:
Number a123;
Number b456789 vit;
Wheareas the expected result should be like below:
a123
b456789
Can anyone help on this?
Perls grep function selects/filters all elements from a list that match a certain condition. In your case, you selected all elements that match the regex /Number/ from the #input_file array.
To select the non-whitespace string after Number use this Regex:
my $regex = qr{
Number # Match the literal string 'Number'
\s+ # match any number of whitespace characters
([^\s;]+) # Capture the following non-spaces-or-semicolons into $1
# using a negated character class
}x; # use /x modifier to allow whitespaces in pattern
# for better formatting
My suggestion would be to loop directly over the input file handle:
while(defined(my $line = <$input>)) {
$line =~ /$regex/;
print "Found: $1" if length $1; # skip if nothing was found
}
If you have to use an array, a foreach-loop would be preferable:
foreach my $line (#input_lines) {
$line =~ /$regex/;
print "Found: $1" if length $1; # skip if nothing was found
}
If you don't want to print your matches directly but to store them in an array, push the values into the array inside your loop (both work) or use the map function. The map function replaces each input element by the value of the specified operation:
my #result = map {/$regex/; length $1 ? $1 : ()} #input_file;
or
my #result = map {/$regex/; length $1 ? $1 : ()} <$input>;
Inside the map block, we match the regex against the current array element. If we have a match, we return $1, else we return an empty list. This gets flattened into invisibility so we don't create an entry in #result. This is different form returning undef, what would create an undef element in your array.
if your script is intended as a simple filter, you can use
$ cat FILE | perl -nle 'print $1 if /Number\s+([^\s;]+)/'
or
$ cat FILE | perl -nle 'for (/Number\s+([^\s;]+)/g) { print }'
if there can be multiple occurences on the same line.
perl -lne 'if(/Number/){s/.*\s([a-zA-Z])([\d]+).*$/\1\2/g;print}' your_file
tested below:
> cat temp
Number a123;
Number b456789 vit;
alphabet fty;
> perl -lne 'if(/Number/){s/.*\s([a-zA-Z])([\d]+).*$/\1\2/g;print}' temp
a123
b456789
>
If I have one variable : I assigned entire file text to it
$var = `cat file_name`
Suppose in the file , the word 'mine' comes in 17th line (location is not available but just giving example) and I want to search a pattern 'word' after N (eg 10) lines of word 'mine' if pattern 'word' exist in those lines or not. How can i do that in the regular expression without using array'
Example:
$var = "I am good in perl\n but would like to know about the \n grep command in details";
I want to search particular pattern in specific lines (lines 2 to 3 only). How can I do it without using array.
There is a valid case for not using arrays here - when files are prohibitively large.
This is a pretty specific requirement. Rather than beat around the bush to find that Perl idiom, I'd prescribe a subroutine:
sub n_lines_apart {
my ( $file, $n, $first_pattern, $second_pattern ) = #_;
open my $fh, '<', $file or die $!;
my $lines_apart;
while (<$fh>) {
$lines_apart++ if qr/$first_pattern/ .. qr/$second_pattern/;
}
return $lines_apart && $lines_apart <= $n+1;
}
Caveat
The sub above is not designed to handle multiple matches in a single file. Let that be an exercise for the reader.
You can do this with a regular expression match like this:
my $var = `cat $filename`;
while ( $var =~ /foo/g ) {
print $1, "\n";
print "match occurred at position ", pos($var), " in the string.\n";
}
This will print out all the matches of the string 'foo' from your string, similar to grep but not using an array (or list). The /$regexp/g syntax makes the regular expression iteratively match against the string from left to right.
I'd recommend reading perlrequick for a tutorial on matching with regular expressions.
Try this:
perl -ne '$m=$. if !$m && /first-pattern/;
print if $m && ($.-$m >= 2 && $.-$m <= 3) && /second-pattern/'