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Perl replace 20 with space betweenАвтор: Maujinn | Category: Samdani forex | Октябрь 2, 2012
One fairly straightforward approach would be to replace the first "hash" by In regex variants that provide it, like Perl, you could use. I've never seen a fancy awk field separator like that before. Cool! – Joe. Apr 8, at Add a comment. fattahsafa has asked for the wisdom of the Perl Monks concerning the Before replacement: 'Line 1 Line 2 Line 3 ' After replacement. BOOKMAKER ODDS
Instead, they must be encoded in any of several available output formats. Internally, Perl uses a format called UTF-8, but many other encoding formats for Unicode exist, and Perl can work with those, too. The use encoding pragma tells Perl in which encoding your script itself has been written, or which encoding the standard filehandles should use.
The use open pragma can set encoding defaults for all handles. Special arguments to open or to binmode specify the encoding format for that particular handle. The -C command-line flag is a shortcut to set the encoding on all or just standard handles, plus the program arguments themselves. Accessing Substrings Problem You want to access or modify just a portion of a string, not the whole thing. Solution The substr function lets you read from and write to specific portions of the string.
Instead of using array subscripting to access individual characters as you sometimes do in other programming languages, in Perl you use functions like unpack or substr to access individual characters or a portion of the string. If the offset is 0, the substring starts at the beginning. The count argument is the length of the substring. For the record, the others are vec, pos, and keys.
If you squint, local, my, and our can also be viewed as lvaluable functions. Specify a format describing the layout of the record to unpack. For positioning, use lowercase "x" with a count to skip forward some number of bytes, an uppercase "X" with a count to skip backward some number of bytes, and an " " to skip to an absolute byte offset within the record. For example, you might want to place cuts right before positions 8, 14, 20, 26, and Those are the column numbers where each field begins.
Let Perl figure it out for you. See Also The pack, unpack, and substr functions in perlfunc 1 and in Chapter 29 of Programming Perl; use of the cut2fmt subroutine in Recipe 1. It often happens that you want a hardcoded default value for a variable that can be overridden from the command line or through an environment variable. They just return the first one that makes the whole expression true or false. In all other cases when the user gives an argument , we use the first argument.
The first expression that returns a true value will be used. One use is demonstrated in Recipe It may already do so by the time you read this text. These defined-or operators will work just like the logical-or operators, , except that they will test definedness, not mere truth. It is expected to be in v5. See Also The operator in perlop 1 and Chapter 3 of Programming Perl; the defined and exists functions in perlfunc 1 and Chapter 29 of Programming Perl 1.
Solution Use list assignment to reorder the variables. Converting Between Characters and Values Problem You want to print the number represented by a given character, or you want to print a character given a number. However, Perl understands more than that: it also has integrated support for Unicode, the universal character encoding. See Also The chr, ord, printf, sprintf, pack, and unpack functions in perlfunc 1 and Chapter 29 of Programming Perl 1.
Using Named Unicode Characters Problem You want to use Unicode names for fancy characters in your code without worrying about their code points. Discussion The use charnames pragma lets you use symbolic names for Unicode characters. Several subpragmas are supported. The :full subpragma grants access to the full range of character names, but you have to write them out in full, exactly as they occur in the Unicode character database, including the loud, all-capitals notation.
The :short subpragma gives convenient shortcuts. Any import without a colon tag is taken to be a script name, giving case-sensitive shortcuts for those scripts. Needing to process anything a character at a time is rare. Usually some kind of higher-level Perl operation, like pattern matching, solves the problem more handily.
See, for example, Recipe 7. Splitting on a pattern that matches the empty string returns a list of individual characters in the string. Instead of using index and substr or split and unpack, it might be easier to use a pattern. Instead of computing a bit checksum by hand, as in the next example, the unpack function can compute it far more efficiently. There are better checksums; this just happens to be the basis of a traditional and computationally easy checksum.
You can use the standard[ 1 ] Digest::MD5 module if you want a more robust checksum. The idea here is to pause after each character is printed so you can scroll text before an audience slowly enough that they can read it. Example Reversing a String by Word or Character Problem You want to reverse the words or characters of a string.
Called in scalar context, it joins together its arguments and returns that string in reverse order. Called in list context, it returns its arguments in the opposite order. It causes split to use contiguous whitespace as the separator and also discard leading null fields, just like awk. Normally, split discards only trailing null fields.
Due to the presence of precombined characters, for the most part to accommodate legacy character systems, there can be two or more ways of writing the same thing. These characters might be encoded into a two-byte sequence under the UTF-8 encoding that Perl uses internally, but those two bytes still only count as one single character. That works just fine.
There are times when you want Perl to treat each combined character sequence as one logical character. Consider the approaches for reversing a word by character from the previous recipe. By grabbing entire sequences of a base character plus any combining characters that follow, then reversing that list, this problem is avoided. How can you get Perl to consider them the same strings? Solution When you have otherwise equivalent strings, at least some of which contain Unicode combining character sequences, instead of comparing them directly, compare the results of running them through the NFD function from the Unicode::Normalize module.
Sometimes this is because of legacy encodings, such as the letters from Latin1 that contain diacritical marks. Another possibility is that you have two or more marks following a base character, but the order of those marks varies in your data.
Several are provided, including NFD for canonical decomposition and NFC for canonical decomposition followed by canonical composition. Solution The use bytes pragma makes all Perl operations in its lexical scope treat the string as a group of octets. Each individual string has a flag associated with it, identifying the string as either UTF-8 or octets. Sometimes you need to work with bytes and not characters. For example, many protocols have a Content-Length header that specifies the size of the body of a message in octets.
The use bytes pragma makes all Perl functions in its lexical scope use octet semantics for strings instead of character semantics. Under this pragma, length always returns the number of octets, and read always reports the number of octets read. For this you need to create an octet-encoded copy of the UTF-8 string.
In memory, of course, the same byte sequence is used for both strings. However, these functions are less useful because not all octet strings are valid UTF-8 strings, whereas all UTF-8 strings are valid octet strings. See Also The documentation for the bytes pragma; the documentation for the standard Encode module 1. Expanding and Compressing Tabs Problem You want to convert tabs in a string to the appropriate number of spaces, or vice versa. Converting spaces into tabs can be used to reduce file size when the file has many consecutive spaces.
The standard textbook method does not use the Text::Tabs module but suffers slightly from being difficult to understand. This is explained in Special Variables in Chapter 6. Its origins date to when Perl ran the first incredibly faster than the second. While the second is now almost as fast, it remains convenient, and the habit has stuck. We need to evaluate the result again to get the value of the variable. Only the first one is compiled and syntax-checked with the rest of your program. A tremendous advantage is that unlike symbolic dereferencing, this mechanism finds lexical variables created with my, something symbolic references can never do.
We have written it the more explicit way for clarity, not correctness. Controlling Case A string in uppercase needs converting to lowercase, or vice versa. You can set the case of either just the first character or the whole string. You can even do both at once to force uppercase actually, titlecase; see later explanation on initial characters and lowercase on the rest. This lets you converse with year-old WaREz d00Dz. This is a mistake because it omits all characters with diacritical markings—such as diaereses, cedillas, and accent marks—which are used in dozens of languages, including English.
However, correctly handling case mappings on data with diacritical markings can be far trickier than it seems. See the section on The Universal Character Code in the Introduction to this chapter for more information. Properly Capitalizing a Title or Headline Problem You have a string representing a headline, the title of book, or some other work that needs proper capitalization. Assume the tc function is as defined in the Solution.
Some prepositions on the list might also double as words that should always be capitalized, such as subordinating conjunctions, adverbs, or even adjectives. Interpolating Functions and Expressions Within Strings Problem You want a function call or expression to expand within a string. This lets you construct more complex templates than with simple scalar variable interpolation.
Your account is now closed. Although these techniques work, simply breaking your work up into several steps or storing everything in temporary variables is almost always clearer to the reader. Indenting Here Documents Problem When using the multiline quoting mechanism called a here document, the text must be flush against the margin, which looks out of place in the code. You would like to indent the here document text in the code, but not have the indentation appear in the final string value.
It removes leading whitespace from the text of the here document. This means they will remove any blank lines in your here document. This lets us do it all in one line, but works only when assigning to a variable. You are a liar, Saruman, and a corrupter of men's hearts.
Another embellishment is to use a special leading string for code that stands out. And whither then? I cannot say. It expects to be called with a here document as its argument. It checks whether each line begins with a common substring, and if so, strips that off. Otherwise, it takes the amount of leading whitespace found on the first line and removes that much from each subsequent line.
This may be one of those cases. In our case, World matches the second word in "Hello World", so the expression is true. This idea has several variations. Some characters, called metacharacters, are considered special, and reserved for use in regex notation. Most of the metacharacters aren't always special, and other characters such as the ones delimiting the pattern become special under various circumstances. This can be confusing and lead to unexpected results.
Arbitrary bytes are represented by octal escape sequences, e. There are a number of different types of character classes, but usually when people use this term, they are referring to the type described in this section, which are technically called "Bracketed character classes", because they are denoted by brackets [ But we'll drop the "bracketed" below to correspond with common usage.
Character classes also have ordinary and special characters, but the sets of ordinary and special characters inside a character class are different than those outside a character class. Both [ See "Backslash sequences" in perlrecharclass for details. To match dog or cat, we form the regex dog cat.
As before, Perl will try to match the regex at the earliest possible point in the string. At each character position, Perl will first try to match the first alternative, dog. If dog doesn't match, Perl will then try the next alternative, cat. If cat doesn't match either, then the match fails and Perl moves to the next position in the string. Here, all the alternatives match at the first string position, so the first matches.
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I'm more interested these days in getting other people interested in computers and programming, maybe trying to inspire other people especially kids to get into it. I'm always going back to the basics and really trying to break concepts down so they are accessible and so I understand them better myself. My hope is to one day either write a programming book for kids, that recaptures some of that wonder and excitement, or develop a series of YouTube tutorials that may help newbies pick up programming in a way that is more accessible and easily understood.
It's not like the old days where you turned your computer on and it booted in a few seconds into a BASIC command prompt. Those systems were a lot of fun because you had to pick up programming right from the start in order to really do anything with them. My hope is to one day either write a programming book for kids, that recaptures some of that wonder and excitement, or develop a series of YouTube tutorials that may help newbies pick up programming in a way that is more accessible and easily understood.
It's not like the old days where you turned your computer on and it booted in a few seconds into a BASIC command prompt. Those systems were a lot of fun because you had to pick up programming right from the start in order to really do anything with them.
Either way, this site Stack Overflow has been a tremendous help to me and a lot of fun to contribute to. Updated on June 04,
Perl replace 20 with space between dash nowPerl Regular Expressions Wrapup
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