命令简介：

该命令用来识别文件类型，也可用来辨别一些文件的编码格式。它是通过查看文件的头部信息来获取文件类型，而不是像Windows通过扩展名来确定文件类型的。

执行权限 ：All User

指令所在路径：/usr/bin/file

命令语法：

file [ -bchikLnNprsvz ] [ -f namefile ] [ -F separator ] [ -m magicfiles ] file ... 

使用示例：

1：查看file命令的帮助信息

代码如下:

[root@DB-Server ~]# file --help

Usage: file [OPTION]... [FILE]...
Determine file type of FILEs.  

-m, --magic-file LIST      use LIST as a colon-separated list of magic                               number files 

-z, --uncompress           try to look inside compressed files 
-b, --brief                do not prepend filenames to output lines 
-c, --checking-printout    print the parsed form of the magic file, use in                               conjunction with -m to debug a new magic file                               before  installing it 
-f, --files-from FILE      read the filenames to be examined from FILE 
-F, --separator string     use string as separator instead of `:' 
-i, --mime                 output mime type strings 
-k, --keep-going           don't stop at the first match 
-L, --dereference          causes symlinks to be followed  -n, --no-buffer do not buffer output 
-N, --no-pad               do not pad output 
-p, --preserve-date        preserve access times on files 
-r, --raw                  don't translate unprintable chars to \ooo 
-s, --special-files        treat special (block/char devices) files as                             ordinary ones     
 --help                 display this help and exit     
 --version              output version information and exit
当然你也可以使用 man file 获取更加详细的帮助文档信息。

2：不输出文件名称，只显示文件格式以及编码

通过下面两个命令对时，就可以清晰的了解参数-b的作用。

代码如下:

[root@DB-Server ~]# file Temp.txt Temp.txt: UTF-8 Unicode text, with very long lines, with CRLF line terminators[root@DB-Server ~]# file -b Temp.txtUTF-8 Unicode text, with very long lines, with CRLF line terminators

3.输出mime类型的字符串

[ai@Database1 nggprs]$ file -i nggprs_group_201702.0000 

nggprs_group_201702.0000: text/plain; charset=us-ascii

4.查看文件中的文件名的文件类型

这个参数非常适合shell脚本去查找、判别某种文件类型的数据。

你可以像下面这样使用 file 命令确定文件的类型。下面的截图显示了用 file 命令确定不同文件类型的例子。

tecmint@tecmint ~/Linux-Tricks $ dir

BACKUP                    master.zip

cro***oads-stable.tar.gz          num.txt
EDWARD-MAYA-2011-2012-NEW-REMIX.mp3   reggea.xspf
Linux-Security-Optimization-Book.gif  tmp-link
tecmint@tecmint ~/Linux-Tricks $ file BACKUP/
BACKUP/: directory
tecmint@tecmint ~/Linux-Tricks $ file master.zip
master.zip: Zip archive data, at least v1.0 to extract
tecmint@tecmint ~/Linux-Tricks $ file cro***oads-stable.tar.gz
cro***oads-stable.tar.gz: gzip compressed data, from Unix, last modified: Tue Apr  5 15:15:20 2011
tecmint@tecmint ~/Linux-Tricks $ file Linux-Security-Optimization-Book.gif
Linux-Security-Optimization-Book.gif: GIF p_w_picpath data, version 89a, 200 x 259
tecmint@tecmint ~/Linux-Tricks $ file EDWARD-MAYA-2011-2012-NEW-REMIX.mp3
EDWARD-MAYA-2011-2012-NEW-REMIX.mp3: Audio file with ID3 version 2.3.0, contains: MPEG ADTS, layer III, v1, 192 kbps, 44.1 kHz, JntStereo
tecmint@tecmint ~/Linux-Tricks $ file /dev/sda1
/dev/sda1: block special
tecmint@tecmint ~/Linux-Tricks $ file /dev/tty1
/dev/tty1: character special

5.尝试去解读压缩文件的内容

[root@DB-Server ~]# file -z Temp.txt.gz Temp.txt.gz: UTF-8 Unicode text, with very long lines, with CRLF line terminators (gzip compressed data, was "Temp.txt", from Unix, last modified: Tue Jun 24 00:34:15 2014)[root@DB-Server ~]#

6.查看软链接对应文件的文件类型

如下所示，创建一个软链接sfile，然后分别用file 和带参数的file -L查看

[root@DB-Server ~]# ln -s Temp.txt.gz sfile[root@DB-Server ~]# file sfile sfile: symbolic link to `Temp.txt.gz'[root@DB-Server ~]# file -L sfile sfile: gzip compressed data, was "Temp.txt", from Unix, last modified: Tue Jun 24 00:34:15 2014[root@DB-Server ~]# 

bey ! thank you!