The file command tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed.
The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCIIterminal), executable (the file contains the result of compiling a program in a form understandable to a kernel), or data meaning anything else (usually binary or non-printable). Exceptions are well-known file formats (core files, tararchives) that are known to contain binary data.
The filesystem tests are based on examining the return from a stat system call. The program checks to see if the file is empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system header file .
The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) a.out file, whose format is defined in , and possibly in the standard include directory. These files have a "magic number" stored in a particular place near the beginning of the file that tells the operating system that the file is a binary executable, and which of several types thereof. The concept of a "magic" has been applied by extension to data files. Any file with some invariant identifier at a small fixed offset into the file can usually be described in this way. The information identifying these files is read from /etc/magic and the compiled magic file /usr/share/misc/magic.mgc, or the files in the directory /usr/share/misc/magic if the compiled file does not exist. Also, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used in preference to the system magic files.
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 IBMPC 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 will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only "character data" because, while they contain text, it is text that will require translation before it can be read. Also, the file will attempt 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 will also be identified.
Once file has determined the character set used in a text-type file, it will attempt 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, just 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."
Do not prepend file names to output lines (brief mode).
-C, --compile
Write a magic.mgc output file that contains a pre-parsed version of the magic file or directory.
-c, --checking-printout
Cause a checking printout of the parsed form of the magic file. This option is usually used in conjunction with the -m flag to debug a new magic file before installing it.
-e, --excludetestname
Exclude the test named in testname from the list of tests made to determine the file type. Valid test names are:
apptype
EMX application type (only on EMX).
ascii
Various types of text files (this test will try to guess the text encoding, irrespective of the setting of the ‘encoding’ option).
encoding
Different text encodings for soft magic tests.
tokens
Ignored for backward compatibility.
cdf
Prints details of Compound Document Files.
compress
Checks for, and looks inside, compressed files.
elf
Prints ELF file details.
soft
Consults magic files.
tar
Examines tar files.
-F, --separatorseparator
Use the specified string separator as the separator between the file name and the file result returned. Defaults to ‘:’.
-f, --files-fromnamefile
Read the names of the files to be examined from namefile (one per line) before the argument list. Either namefile or at least one file name argument must be present; to test the standard input, use ‘-’ as a file name argument. Please note that namefile is unwrapped and the enclosed file names are processed when this option is encountered and before any further options processing is done. This option allows one to process multiple lists of files with different command line arguments on the same file invocation. Thus if you want to set the delimiter, you need to do it before you specify the list of files, like: "-F @ -f namefile", instead of: "-f namefile -F @".
-h, --no-dereference
option causes symlinks not to be followed (on systems that support symbolic links). This option is the default if the environment variable POSIXLY_CORRECT is not defined.
-i, --mime
Causes the file command to output mime type strings rather than the more traditional human readable ones. Thus it may say ‘text/plain; charset=us-ascii’ rather than "ASCII text".
--mime-type, --mime-encoding
Like -i, but print only the specified element(s).
-k, --keep-going
Don't stop at the first match, keep going. Subsequent matches will be have the string ‘\012- ’ prepended. (If you want a newline, see the -r option.)
-l, --list
Print information about the strength of each magic pattern.
-L, --dereference
option causes symlinks to be followed, as the like-named option in ls (on systems that support symbolic links). This option is the default if the environment variable POSIXLY_CORRECT is defined.
-l
Shows sorted patterns list in the order that is used for the matching.
-m, --magic-filemagicfiles
Specify an alternate list of files and directories containing magic. This option can be a single item, or a colon-separated list. If a compiled magic file is found alongside a file or directory, it will be used instead.
-N, --no-pad
Don't pad file names so that they align in the output.
-n, --no-buffer
Force stdout to be flushed after checking each file. This option is only useful if checking a list of files. It is intended to be used by programs that want filetype output from a pipe.
-p, --preserve-date
On systems that support utime or utimes, attempt to preserve the access time of files analyzed, to pretend that file never read them.
-r, --raw
Don't translate unprintable characters to \ooo. Normally file translates unprintable characters to their octal representation.
-s, --special-files
Normally, file only attempts to read and determine the type of argument files which stat reports are ordinary files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s option causes file to also read argument files that are block or character special files. This option is useful for determining the filesystem types of the data in raw disk partitions, which are block special files. This option also causes file to disregard the file size as reported by stat since on some systems it reports a zero size for raw disk partitions.
-v, --version
Print the version of the program and exit.
-z, --uncompress
Try to look inside compressed files.
-0, --print0
Output a null character ‘\0’ after the end of the file name, which is helpful if, for instance, you'd like to cut the output. This option does not affect the separator, which is still printed.
--help
Print a help message and exit.
查看英文版
查看中文版
file 例子
file *
下面是運行時，可能會出現什么樣的例子file與所有文件通配符：
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
file *.txt
下面是運行上述示例時可能顯示的示例；運行file命令列出任何以.txt結尾的文件：
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
file *
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
file *.txt
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
file (報告文件的類型)
在類似Unix的操作系統上，file命令報告文件的類型。
On Unix-like operating systems, the file command reports a file's type.
查看英文版
查看中文版
1 file 運行系統環境
2 file 描述
3 file 語法
4 file 例子
file 運行系統環境
Unix&Linux
file 描述
該file命令測試每個參數，企圖對其進行分類。有三組測試，按此順序執行：file系統測試，魔術測試和語言測試。第一個成功的測試導致打印file類型。
可打印的類型通常將包含以下單詞之一：文本（file僅包含打印字符和一些常見的控制字符，并且可能在ASCII 終端上可以安全讀取），可執行（file包含以某種形式編譯程序的結果）對于內核是可以理解的），或表示其他含義的數據（通常是二進制或不可打印的）。例外是眾所周知的包含二進制數據的file格式（核心file，tar 歸檔file）。
file系統測試基于檢查stat系統調用的返回結果。程序檢查file是否為空，或者是否為某種特殊file。如果在系統頭file
魔術測試用于檢查帶有特定固定格式數據的file。一個典型的例子是一個二進制可執行file（編譯程序）a.outfile，其格式定義為標準include目錄中的
如果file與魔術file中的任何條目都不匹配，那么將檢查該file是否似乎是文本file。ASCII，ISO -8859-x，非ISO 8位擴展ASCII字符集（例如在Macintosh和IBM PC系統上使用的字符集），UTF -8編碼的Unicode，UTF-16編碼的Unicode和EBCDIC字符集可以通過構成每個集合中可打印文本的字節的不同范圍和順序來區分。如果file通過了這些測試中的任何一個，則報告其字符集。ASCII，ISO-8859-x，UTF-8和擴展ASCIIfile被標識為“文本”，因為它們幾乎可以在任何終端上讀?。籙TF-16和EBCDIC只是“字符數據”，因為盡管它們包含文本，但這些文本需要翻譯才能被讀取。此外，file將嘗試確定文本類型file的其他特征。如果file的行以CR，CR LF或NEL而不是Unix標準LF終止，則將報告此錯誤。包含嵌入式轉義序列或過分敲擊的file也將被識別。
一旦file確定了文本類型file中使用的字符集，它將嘗試確定file以哪種語言編寫。語言測試尋找可以出現在file前幾個塊中任何位置的特定字符串（參見
不能識別為已用上面列出的任何字符集寫入的任何file都稱為“數據”。
The file command tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed.
The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a program in a form understandable to a kernel), or data meaning anything else (usually binary or non-printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data.
The filesystem tests are based on examining the return from a stat system call. The program checks to see if the file is empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system header file
The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) a.out file, whose format is defined in
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 will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only "character data" because, while they contain text, it is text that will require translation before it can be read. Also, the file will attempt 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 will also be identified.
Once file has determined the character set used in a text-type file, it will attempt to determine in what language the file is written. The language tests look for particular strings (cf.
Any file that cannot be identified as having been written in any of the character sets listed above is said to be "data."
查看英文版
查看中文版
file 語法
file [-bchiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] file ...選件
file [-bchiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] file ...Options
查看英文版
查看中文版
file 例子
下面是運行時，可能會出現什么樣的例子file與所有文件通配符：
下面是運行上述示例時可能顯示的示例；運行file命令列出任何以.txt結尾的文件：
Below is an example of what may appear when running file with a wildcard for all files:
Below is an example of what may appear when running the above example; running the file command listing any file ending with .txt:
查看英文版
查看中文版
其他命令行
fc | fdisk | fg | fgrep | findsmb | finger | fmt | fold | for | free | fuser |