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How can I detect and show an error if someone put a letter and the program expects a number?
A regexp match makes this easy. Searching for any character which isn't a numeral or an arithmetic symbol:
if ( $input =~ /[^0-9+*/-]/ ) {
print "Incorrect character detected!\n"
}
Literally anything which is a letter:
if ( $input =~ /[A-Za-z]/ ) {
print "Incorrect character detected!\n"
}
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such string:
interface Loopback0 description "Loopback Interface for network management" ip address 10.20.30.40 255.255.255.255 no ip proxy-arp
how to print what is between " "?
Loopback Interface for network management
Assuming that the " character occurs only 2 times or if you want the first pair:
# Get the indices of the " characters
ind1 = exampleStr.find('"')
ind2 = exampleStr.find('"', ind1+1)
# Get the substring between the two indices
result = exampleStr[ind1+1:ind2]
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I have an array in the third element dataArr[2], I know it contains a 10 digit phone. I need to only read or print the first 6 digits. For instance if my phone is 8329001111, I need to print out the 832900. I tried to see if I can use substr but I keep reading or printing the full list. Do I need to dereference..
Try this :
$dataArr[2] =~ s/\s//g; # ensure there's no spaces
print substr($dataArr[2], 0, 6);
# ^ ^ ^
# variable | |
# offset start|
# |
# substring length
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Can someone explain what the second half of this script does? (second line)
$self is defined elsewhere... (I know what that part does, Just wondering what the action=~... is all about/)
$action = "http://example.com/test.php";
$action = $self->{url} . ($action =~ /^\// ? "" : "/" ) . $action;
It returns an empty string if $action starts with a slash, and a slash if it does not start with a slash.
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I have file as below.
ID || DATE || AMOUNT
XX||20130801##20130901##20131001##20131101||100##200##300##400
and I want the output as below using perl.
xx||20130801||100
xx||20130901||200
xx||20131001||300
xx||20131101||400
Please help me how to convert using perl.
perl -F'\|\||##' -lanE'$.>1 or $" ="||",next; say "#F[0,$_,$_+4]" for 1..4' file
perl -F'\|\|' -lane '#a=split(/##/,$F[1]); #b=split(/##/,$F[2]); print "$F[0]||$a[$_]||$b[$_]" foreach 0..$#a;' file
Output:
ID || DATE || AMOUNT
XX||20130801||100
XX||20130901||200
XX||20131001||300
XX||20131101||400
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In lex, I can define the following starting condition for equations defined between $...$.
%x EQN1
\$ { BEGIN(EQN1); }
<EQN1>{
\$ { BEGIN(INITIAL); }
[^\$]* {}
}
For equations between $$...$$, how can I define the anything but $$ rule, such as in [^\$]*. I guess [^\$\$]* wouldn't work.
I think you don't understand the way the patterns are matched, see flex manual
Flex always try to match longest input possible. You can understand it in way, that longer rules have higher priority.
Because "\$\$" match two characters and "." just one, the example below will work just fine.
%x EQN2
\$\$ { BEGIN(EQN2); }
<EQN2>{
\$\$ { BEGIN(INITIAL); }
. {}
}
You can also replace [^\$]* {} with . {} in your example, because when rules match same size of input, the first one in lex.l has higher priority.