File command linux data

If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the different ranges and sequences of bytes that constitute printable text in each set. If a file passes any of these tests, its character set is reported. ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as «text» because they are mostly readable on nearly any terminal; UTF-16 and EBCDIC are only «character data» because, while they contain text, it is text that requires translation before it can be read. Also, the file attempts to determine other characteristics of text-type files. If the lines of a file are terminated by CR, CR LF, or NEL, instead of the Unix-standard LF, this will be reported. Files that contain embedded escape sequences or overstriking is also identified.

Once file has determined the character set used in a text-type file, it attempts to determine in what language the file is written. The language tests look for particular strings (cf. ) that can appear anywhere in the first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff input file, as the keyword struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The language test routines also test for some miscellany (such as tar archives).

Any file that cannot be identified as having been written in any of the character sets listed above is said to be «data.»

Syntax

file [-bchiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] file .

Options

Examples

Below is an example of what may appear when running file with a wildcard for all files:

shutdown.htm: HTML document text si.htm: HTML document text side0.gif: GIF image data, version 89a, 107 x 18 robots.txt: ASCII text, with CRLF line terminators routehlp.htm: HTML document text rss: setgid directory

Below is an example of what may appear when running the above example; running the file command listing any file ending with .txt:

form.txt: news or mail text friend.txt: news or mail text ihave.txt: news or mail text index.txt: ASCII Java program text, with very long lines, with CRLF line terminators jargon.txt: news or mail text news.txt: Non-ISO extended-ASCII C program text, with very long lines, with CRLF line terminators newsdata.txt: Non-ISO extended-ASCII English text, with very long lines, with CRLF line terminators qad.txt: news or mail text refrence.txt: news or mail text robots.txt: ASCII text, with CRLF line terminators stopwords.txt: ASCII English text, with CRLF line terminators yhelp.txt: news or mail text

Related commands

ls — List the contents of a directory or directories.

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Essential Examples of the File Command in Linux

Here are various examples of the file command in Linux to determine the actual type of file and gather related information.

You have seen commands to create file in Linux. You have also seen the command to delete file in Linux. Let’s talk about the file command in this article.

What is the file command in Linux and Unix?

How do you recognize the type of a file? Let me guess, by its extension, right? I mean if you see a file named MyData.csv, you guess that the file is in CSV format. You can make sure of that by viewing the file content.

But the file extensions in Linux and Unix have no real meaning. You can name a csv file, a zip file. You can choose to not use any extension at all.

The file command comes handy in such situations. The file command in Linux determines the actual type of a file, no matter what its extension is.

It has a simple syntax with only a few options:

Now that you know the syntax let’s see how to use the file command.

Example of file command in Linux

In its simplest form, you can use the file command with filename or path to file and it will show the type of the file.

[email protected]:~/$ file cpluplus.cpp cpluplus.cpp: C++ source, ASCII text

Let’s see some other ways you can use it with its options.

Remove filename from the output

You can use the option -b and the output will show only the file type omitting the filename. It could be useful in scripting.

Have a look at the same example you saw earlier:

[email protected]:~/$ file -b cpluplus.cpp C++ source, ASCII text

Get the mime type of the file

You can also display the MIME type of the file thanks to the -i option.

Here’s an example of the command on a video file, with and without MIME type info:

[email protected]:~/$ file my_video.mp4 my_video.mp4: ISO Media, MP4 v2 [ISO 14496-14] [email protected]:~/$ file -i my_video.mp4 my_video.mp4: video/mp4; charset=binary

You can combine -b and -i options.

Get file type info of a file inside an archive file

If you gzip a directory and now you have a compressed file. You can examine the uncompressed contents to decide the file type with -z option.

Let me show you an example with and without the -z option:

[email protected]:~/$ file author-pro.zip author-pro.zip: Zip archive data, at least v2.0 to extract [email protected]:~/$ file -z author-pro.zip author-pro.zip: PHP script, ASCII text (Zip archive data, at least v2.0 to extract)

Use file command with multiple files

File command can be run on multiple files simultaneously.

Here’s an example for you so that you can see it in action:

[email protected]:~/$ file cpluplus.cpp agatha.txt bash_script.sh cpluplus.cpp: C++ source, ASCII textagatha.txt: ASCII text bash_script.sh: Bourne-Again shell script, ASCII text executable

Use file command with regex

If you want to use the file command on multiple files, you don’t always have to provide all the filenames. You can use regex instead.

It’s really up to your requirement and imagination how you could use it. I’ll show some examples nevertheless.

If you want to display file type of all the files in the current directory, simply use this:

If you want to display file type of all the files with a certain extension, you can do that as well:

The possibilities are endless. Want to display file type of files with name starting with ‘a’? Use this:

Other options you may use with file command

Here are a few other options with file command that you may use:

• -L : Follow symbolic links and report the type of the destination file
• -f file_name : Read filenames line by line from the given file_name and report their file type

There are a few other options as well but I believe you have learned all the essential examples of the Linux file command. If you have questions or suggestions, do let me know in the comment section.

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