#ver = $session->cmd("sh conf");
The variable here is ver, which has the configuration file, that is, it has more than one line. So how to take an output of each line of the ver variable without putting it in a loop?
Your #var variable is an array - each element will contain one line.
You cannot get all lines without (implicitly or explicitly) looping over the entire array.
You can have perl do all the work for you though - for example, using join, grep or map, depending what you want.
Examples:
#print all lines to a webpage
print join('<br />',#ver);
#print all lines with the word 'error' in it
print grep(/error/,#ver);
How about :
print join("\n", #ver);
Related
I am trying to read below CSV file content line by line in Perl.
CSV File Content:
A7777777.A777777777.XXX3604,XXX,3604,YES,9
B9694396.B216905785.YYY0018,YYY,0018,YES,13
C9694396.C216905785.ZZZ0028,ZZZ,0028,YES,16
I am able to split line content using below code and able to verify the content too:
#column_fields1 = split(',', $_);
print $column_fields1[0],"\n";
I am also trying to find the second part on the first column of CSV file (i.e., A777777777 or B216905785 or C216905785) – the first column delimited with . using the below code and I am unable to get it.
Instead, just a new line printed.
my ($v1, $v2, $v3) = split(".", $column_fields1[0]);
print $v2,"\n";
Can someone suggest me how to split the array element and get the above value?
On my functionality, I need the first column value altogether at someplace and just only the second part at someplace.
Below is my code:
use strict;
use warnings;
my $dailybillable_tab_section1_file = "./sql/demanding_01_T.csv";
open(FILE, $dailybillable_tab_section1_file) or die "Could not read from $dailybillable_tab_section1_file, program halting.";
my #column_fields1;
my #column_fields2;
while (<FILE>)
{
chomp;
#column_fields1 = split(',', $_);
print $column_fields1[0],"\n";
my ($v1, $v2, $v3) = split(".",$column_fields1[0]);
print $v2,"\n";
if($v2 ne 'A777777777')
{
…
…
…
}
else
{
…
…
…
}
}
close FILE;
split takes a regex as its first argument. You can pass it a string (as in your code), but the contents of the string will simply be interpreted as a regex at runtime.
That's not a problem for , (which has no special meaning in a regex), but it breaks with . (which matches any (non-newline) character in a regex).
Your attempt to fix the problem with split "\." fails because "\." is identical to ".": The backslash has its normal string escape meaning, but since . isn't special in strings, escaping it has no effect. You can see this by just printing the resulting string:
print "\.\n"; # outputs '.', same as print ".\n";
That . is then interpreted as a regex, causing the problems you have observed.
The normal fix is to just pass a regex to split:
split /\./, $string
Now the backslash is interpreted as part of the regex, forcing . to match itself literally.
If you really wanted to pass a string to split (I'm not sure why you'd want to do that), you could also do it like this:
split "\\.", $string
The first backslash escapes the second backslash, giving a two character string (\.), which when interpreted as a regex means the same thing as /\./.
If you look at the documentation for split(), you'll see it gives the following ways to call the function:
split /PATTERN/,EXPR,LIMIT
split /PATTERN/,EXPR
split /PATTERN/
split
In three of those examples, the first argument to the function is /PATTERN/. That is, split() expects to be given a regular expression which defines how the input string is split apart.
It's very important to realise that this argument is a regex, not a string. Unfortunately, Perl's parser doesn't insist on that. It allows you to use a first argument which looks like a string (as you have done). But no matter how it looks, it's not a string. It's a regex.
So you have confused yourself by using code like this:
split(".",$COLUMN_FIELDS1[0])
If you had made the first argument look like a regex, then you would be more likely to realise that the first argument is a regex and that, therefore, a dot needs to be escaped to prevent it being interpreted as a metacharacter.
split(/\./, $COLUMN_FIELDS1[0])
Update: It's generally accepted among Perl programmers, that variable with upper case names are constants and don't change their values. By using upper case names for standard variables, you are likely to confuse the next person who edits your code (who could well be you in six months time).
So I am passing an array reference into a function to clear out certain array elements:
The code is as follows:
if($notes->[$x] !~ /[^CF]/)
{
print "$notes->[$x]\n";
splice (#{$notes}), $x, 1;
}
If I comment out the splice line, the loop works fine showing me each $x element of the array. But if I do not comment out the splice comment, it all fails. It won't print out the $x element nor will the splice command work.
Use of uninitialized value in pattern match (m//) at
/var/www/cgi-bin/Funx.pm line 130.
Use of uninitialized value in
concatenation (.) or string at /var/www/cgi-bin/Funx.pm line 132.
Totally unsure as to what's going on here. I can understand my splice line not being the correct syntax. But why it affects the line above it I don't.
Any insight would be appreciated.
First of all
splice(#{$notes}), $x, 1;
should be
splice(#{$notes}, $x, 1);
That's not the error you asked about, but it's the only one you showed.
The error leading to the error message you did obtain is likely an incorrect loop. I believe you are using something along the lines of
for (#$notes)
or
for (0..$#$notes)
The first is buggy because you are not allowed to add or remove elements from an array over which you are iterating.
The second is buggy because it will execute the loop body as many times as the array had elements originally, so you'll end up looping too many times.
I'm still learning Unix and I'm having issues understanding the following line of code.
echo "$lines" | awk '{split($0,a,":"); print a[3],a[2],a[1]}'
I don't understand what is happening with the array a in the line of code above. Is it declaring the array and setting it equal to the string it's parsing? If it is declaring the array a, then, why can't I print out the results later on in the code?
echo "${a[1]}"
The line above prints an empty line and not what has been stored in the array a when the string was parsed. I know there is always something in the string that needs to be parsed and when I call the array a[1] I know that I'm in inside the scope. I just don't see/understand what is happening with the array a that prevents me from printing it out later on in the code.
Your code is printing a line for each line of input. If you dont have get output, my first guess would be, that you don't have input.
Given an input of:
lines="ab:cd:ef
ij:kl:m"
the output is:
ef cd ab
m kl ij
awk is executing the commands (which is everything in between the single quotes) for each line of input. First splitting the input line $0 at each : into an array a, then printing the first three elements in reverse order.
If you try to access an array element in the shell, what echo suggests, then you are too late. The array exists within awk and is gone when awk has finished.
I'm running Ubuntu 14.04 and am trying to fill an array in a shell script so that I can loop over it and utilize its contents to fill a text file. However, there's a snag: it doesn't seem to be filling.
I've simplified the larger script that I'm working with down to the essential issue, reprinted below:
WL_START=1
WL_END=5
WL_INC=1
wl_range=$(seq $WL_START $WL_INC $WL_END)
declare -a WL
for i in $wl_range # loop through sequence and fill array
do
WL[$i]=${wl_range[$i]}
done
echo $wl_range
echo ${wl_range[1]}
echo $WL
echo ${WL[1]}
However, my output looks like this:
1 2 3 4 5
empty line
empty line
empty line
Any ideas? I know that people say to just use seq to fill the array, but I had the same problem there as well.
Too much work.
WL=($(seq $WL_START $WL_INC $WL_END))
wl_range is a string consisting of space-delimited numbers, not an array. Your for loop should simply look like
for i in $wl_range; do
WL[i]=$i
done
That said, don't use the for loop; use #IgnacioVazquez-Abrams' answer.
I am trying to read a file into a temporary variable, filtering the file based off of items in an array. I am doing this by opening a file and in the while loop of reading the file, run another loop (very bad idea IMO) to check to see if the contents match the array, if so the line is discarded and it proceeds to the next line.
It works, but its bad when there are 20,000 lines of input. I am reading with an array of 10 items, which essentially turns it into a 200,000 line file.
Is there a way to process this quicker?
Assuming you want to discard a line if any item in your array is found, the any function from List::MoreUtils will stop searching through an array as soon as it has found a match.
use List::MoreUtils qw(any);
while (<>) {
my $line = $_;
next if any { $line =~ /$_/ } #list;
# do your processing
}
If you happen to know which items in your array are more likely to occur in your lines, you could sort your array accordingly.
You should also Benchmark your approaches to make sure your optimization efforts are worth it.
Mash the array items together into a big regex: e.g., if your array is qw{red white green}, use /(red|white|green)/. The $1 variable will tell you which one matched. If you need exact matching, anchor the end-points: /^(red|white|green)$/.