Steps to get a substring from a string

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

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Re: Steps to get a substring from a string by CountZero (Bishop) on Jul 21, 2015 at 16:48 UTC
Just to make sure I understand you fully. You have the following four patterns of data: `name=servername.xyz.abc.coom` `name=servername` `name=servername.xyz.com` and for each of these patterns you want to extract `servername`. If the above assumptions are correct, the following will do the trick: `use Modern::Perl qw/2015/; while (<DATA>) { chomp; say "$_ => $1" if m/name=([^\.]+)/; } __DATA__ name=servername.xyz.abc.coom name=servername name=servername.xyz.com` [download] Output: `name=servername.xyz.abc.coom => servername name=servername => servername name=servername.xyz.com => servername` [download] update: To be fully compliant with the respective RFCs (see above), the regex should be `m/name=([-0-9a-z]+)/i` CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]
Re^2: Steps to get a substring from a string by Not_a_Number (Prior) on Jul 21, 2015 at 17:34 UTC
`if m/name=([^\.]+)/;` Small remark: there's no need to escape '.' (dot) in a character class.	[reply] [d/l]
Re^3: Steps to get a substring from a string by CountZero (Bishop) on Jul 21, 2015 at 17:45 UTC
I know. It is just a (bad?) habit I have and to be a bit more orthogonal between the use is "." inside and outside of character classes. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply]
Re^2: Steps to get a substring from a string by shroh (Acolyte) on Jul 21, 2015 at 23:21 UTC
Hi Let me reiterate what i told earlier, We have three scenarios: 1) Variable a can be servername.abc.xyz.com 2) It can be servername.xyz.com 3) It can be just servername I all the above cases i am just intereested in servername and if it can be saved in a variable.	[reply]
Re^3: Steps to get a substring from a string by AnomalousMonk (Archbishop) on Jul 22, 2015 at 01:55 UTC
Let me reiterate ... Unfortunately, you're not reiterating anything: none of the example strings you give is the same as any in the OP. I suggest you follow CountZero's approach and post something like I have the following patterns of data: `'name=servername.xyz.abc.coom'` `'name=servername'` `'name=servername.xyz.com'` `'whatever'` ... From each of these patterns I want to extract string. I think I know what you think you want, but why should we play guessing games? The devil is in the details. Update: Also, what version(s) of Perl must you work with? This has implications for the regex constructs that are available. Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]
Re^3: Steps to get a substring from a string by CountZero (Bishop) on Jul 22, 2015 at 06:38 UTC
Wait! You have just changed the data. Before it was of the general form "`name=servername ...`" and now it is "`servername ...`". Different forms of data will need different forms of regexes. Please provide some better information or our help will just be guesswork. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]
Re^3: Steps to get a substring from a string by Anonymous Monk on Jul 22, 2015 at 00:03 UTC
Let me reiterate what CountZero told you earlier `if ($string =~ m/name=([^.]+)/) { my $variable_i_am_interested_in = $1; }` [download]	[reply] [d/l]
Re: Steps to get a substring from a string by Corion (Patriarch) on Jul 21, 2015 at 16:35 UTC
Depending on the parts you have already written and the functionality you need, Mozilla::PublicSuffix might help you to determine what is "a domain" and what is "a hostname in a domain". If your question is only about string manipulation, have you considered using split on a dot and taking the first result? `my @parts = split /\./, $input;` [download]	[reply] [d/l]
Re^2: Steps to get a substring from a string by vinoth.ree (Monsignor) on Jul 21, 2015 at 16:42 UTC
Hi Corion How about the 2nd case,*2) I have name=servername , i want to still capture the first part in a variable.* In this your code will not work. we need to match a-zA-Z character after = `my $str='name=host.com' my ($match) =$string=~/=([a-zA-Z]+)/;` [download] Update: Updated the regex part as per CountZero's node Re^3: Steps to get a substring from a string *All is well. I learn by answering your questions...*	[reply] [d/l]
Re^3: Steps to get a substring from a string by CountZero (Bishop) on Jul 21, 2015 at 17:05 UTC
According to RFC952 and RFC-1123, the hostname should only consists of the ASCII letters 'a' through 'z' (in a case-insensitive manner), the digits '0' through '9', and the hyphen ('-'). Spaces and underscores are not allowed! Update: added "and underscores" CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply]
Re^4: Steps to get a substring from a string by vinoth.ree (Monsignor) on Jul 21, 2015 at 17:10 UTC
Re: Steps to get a substring from a string by vinoth.ree (Monsignor) on Jul 21, 2015 at 16:32 UTC
What did you try so far? show us the code you have tried. *All is well. I learn by answering your questions...*	[reply] [d/l]