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File extension is in extensions list: Difference between revisions
File extension is in extensions list (view source)
Revision as of 12:32, 2 September 2016
, 7 years agorewrite task description, to differentiate this task from Extract file extension
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{{draft task}} [[Category:File_System_Operations]] [[Category:String_manipulation]]
The check should be case insensitive. ▼
[[wp:Filename extension|Filename extensions]] are a rudimentary but commonly used way of identifying files types.
{{task heading}}
Given an arbitrary filename and a list of extensions, tell whether the filename has one of those extensions.
Notes:
* The extension must occur at the very end of the filename, and be immediately preceded by a dot (<code>.</code>).
* You may assume that none of the given extensions are the empty string, and none of them contain a dot. Other than that they may be arbitrary strings.
;''Extra credit:''
: Allow extensions to contain dots. This way, users of your function/program have full control over what they consider as the extension in cases like <code>archive.tar.gz</code>.
: Please state clearly whether or not your solution does this.
{{task heading|Test cases}}
The following test cases all assume this list of extensions: <code>zip</code>, <code>rar</code>, <code>7z</code>, <code>gz</code>, <code>archive</code>, <code>A##</code>
{| class="wikitable"
|-
! Filename
! Result
|-
| <code>My_Data.a##</code> || true
|-
| <code>My_Data.tar.Gz</code> || true
|-
| <code>My_Data.gzip</code> || false
|-
| <code>My_Data.7z.backup</code> || false
|-
| <code>My_Data...</code> || false
|-
| <code>My_Data</code> || false
|}
If your solution does the extra credit requirement, add <code>tar.bz2</code> to the list of extensions, and check the following additional test cases:
{| class="wikitable"
|-
! Filename
! Result
|-
| <code>My_Data_v1.0.tar.bz2</code> || true
|-
| <code>My_Data_v1.0.bz2</code> || false
|}
{{task heading|Motivation}}
Checking if a file is in a certain category of file formats with known extensions (e.g. archive files, or image files) is a common problem in practice, and may be approached differently than extracting and outputting an arbitrary extension ''(see e.g. <code>FileNameExtensionFilter</code> in Java)''.
It also requires less assumptions about the format of an extension, because the calling code can decide what extensions are valid.
For these reasons, this task exists in addition to the [[Extract file extension]] task.
{{task heading|Related tasks}}
* [[Extract file extension]]
* [[String matching]]
<hr>
=={{header|AWK}}==
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