What is a wildcard and what does a wildcard mean

Where do you refer to the wildcard? 1. In the database, (1) Any string containing zero or more characters. where title like '%computer%'All titles that contain the word computer are found anywhere in the title.

2), underscore) any single character. where au_fname like '_ean'All 4-letter names ending in EAN (dean, sean, etc.) will be found. 3), specify any single character in a range ([a-f]) or set ([abcdef]).

where au_lname like '[c-p]arsen'Author's last name that ends in arsen and begins with any single character between c and p, for example, carsen, larsen, karsen, and so on. (4), any single character that does not belong to the specified range ([a-f]) or set ([abcdef]). where au_lname like 'de[^l]%'The last names of all authors starting with de and followed by a letter other than l will be found.

2. In the computer, the following is the · "? It can be used to replace a single character. Can replace any character.

The square bracket "[charset]" replaces any single character in the charset set. Explain the last one. The [cchh] wildcard can be used in place of the case of C or H characters.

Wildcard sets can also describe all characters in between. For example, "[a-z]" can replace any lowercase letter, and [a-za-z] can replace any letter. NoteAlternate characters include characters, including all characters between character pairs.

There are also some other software with wildcard characters, to word. ]

？It can be used to replace a single character.

Can replace any character.

The square bracket "[charset]" replaces any single character in the charset set.

Explain the last one. The [cchh] wildcard can be used in place of the case of C or H characters.

Wildcard sets can also describe all characters in between. For example, "[a-z]" can be substituted.

Replace any lowercase letter, and [a-za-z] can replace any letter. Pay attention to alternate characters.

Include characters includes all characters between character pairs.

UNIX's wildcard mechanics are much better than DOS compared to DOS.

In DOS, anything after the "*", ". .The characters are ignored, so the following instructions will not get the results you want. del *bak.*

In DOS, the user can only use this command to delete all files that are currently under the current command, unless the system wants to.

Please don't. In the UNIX system, "* can be used as a substitute for any number, including 0.

characters, but the rest of the features in a line still need to match, so "bak."*"Matchable."

Even, but not with newbak, because of the post.

does not include"."It's clever and user-friendly, and "*bak" can match that.

All entries, including newbak.

2. Can I use multiple wildcards in one instruction? Yes, such as:

This command can delete a series of temporary output files, such as etc.

UNIX treats related files as part of a set that users can use to match.

So, if you need to delete, just go in:

rm file[0-9].temp

The usefulness of this trick is that you can delete the files that you want to delete. If you want to work for one every day.

The very important database makes a "dump" report where you deposit the file into the dumpdate%h%d, which includes a series of files as follows: jun24dump

Let's assume that because each file has a capacity of about 100m, the disk space will be filled up quickly, so you need to delete some old files every few days, leaving only the last two files, and for this, type:

This directive would delete documents that began with "du" and ended with "3" or "4".

A wildcard is a special statement that mainly has an asterisk (*) and a question mark (?).)

Wildcards are used to obfuscate search files. When looking for a folder, you can use it in place of one or more real characters; When you don't know the real characters or don't bother to type in the full name, wildcards are often used instead of one or more real characters. Actually use "*not?".

pad" can correspond to notepad mynotepad [* can represent any string; ?represents only a single string, but the word must exist]; notep[ao]d can correspond to notepad notepod [ao stands for a or o either], and so on.

A wildcard is a special statement that mainly has an asterisk (*) and a question mark (?).) is used to obfuscate the search for files. When looking for a folder, you can use it in place of one or more real characters; When you don't know the real characters or are too lazy to enter the full name slippery orthography, wildcards are often used instead of one or more real characters.

1. Asterisk (*).

You can use an asterisk instead of zero, single, or multiple characters. If you are looking for a file that starts with aew, but you can't remember the rest of the file name, you can enter aew* to find files of all file types that start with aew, such as etc.

To narrow it down, enter aew*txt, find all file types that start with AEW and do not. txt for files with extensions such as:

2. Question mark (?) ）

You can use a question mark instead of a character. If you type love?to find files of a file type that ends with a character starting with love, such as lovey and lovei.

To narrow it down, you can type love?doc, find a file type that ends with a character that starts with love and. doc for files with extensions such as.

Meaning of wildcard:

A special statement, mainly with an asterisk (*) and a question mark, is used to search for files in a fuzzy manner. Wildcards are an advanced feature of PPC ads, and when we use them in our advertising creative, people with different search terms will see different ad creatives.

However, wildcard does not mean this way in the field of SSL certificates, and is referred to as wildcard SSL certificates.

Wildcard SSL certificates, also known as wildcard SSL certificates, can protect a domain name and all sub-domain names of the domain name, without limiting the number of sub-domain names, and adding new subdomains in the future does not need to be re-examined and paid extra.

There are two levels of validation for wildcard certificates: DV SSL (domain name validation) and OV SSL (organization validation).

Wildcard touch sale refers to the use of the * symbol, which represents the meaning of unlimited use, such as the wildcard domain name: *Refers to the unlimited rental of any custom second-level domain name under the domain name of the joke.

Wildcard SSL certificates.

It means that a domain name and all subdomains at the next level of the domain name can be protected.

SSL certificate. For example, if you apply for a wildcard certificate, all second-level subdomains of and can be protected by https and will not increase due to the increase in the number of second-level subdomains.

Wildcard certificates do not limit the number of subdomain names at that level to be protected, usually the state town uses "*" to represent the wildcard, that is, at which level "*" is in, all domain names at that level can be protected back to the closed shed, it can be replaced with any alphanumeric underscore.

Many enterprises often open a lot of subdomain names for ** because of business needs, for example, there is.

And so much more*At this time, applying for a certificate for each subdomain is obviously too cumbersome, the cost will increase a lot, and the management is relatively troublesome. If you use a wildcard certificate, you can get all the second-level subdomains in one card.

If you are only a primary domain name with many Level 2 subdomains that need to be protected by HTTPS, then a standard wildcard SSL certificate can do the trick.

Apply for a wildcard SSL certificate.

* Can be used in place of zero, single or multiple characters, while ? You can use only one character in lieu of one. * indicates that the number of matches is not limited, while ? is limited in the number of matching characters.

Characteristics of wildcards, you can use it instead of one or more real characters, and often use wildcards instead of one or more real characters when you don't know the real characters or are too lazy to enter the full name.

Wildcards are an advanced feature of PPC ads, and when we use them in ad creative, people with different search terms will see different ad creatives (even though we've only created one ad), which will greatly improve the relevance of our ads.

and practicality, thereby increasing the click-through rate of the advertisement, but also greatly improving our work efficiency.

*"Represents any number of characters (including 0)," represents any character.

The wildcards mainly include:

When looking for a folder, you can use a wildcard asterisk in place of one or more real characters.

When you don't know the real characters or don't bother to type the full name, you often use a wildcard question mark instead of one or more real characters.