用途说明
file命令是用来检测并显示文件类型（determine file type）。
常用参数
-b 不显示文件名称，只显示文件类型。在shell脚本中时有用。
-i 显示MIME类别。
-L 直接显示符号连接所指向的文件的类别。
-f namefile 指定名称文件(namefile)，该文件每一行为一个文件名，file命令将按每一行的文件名辨别该文件的类型
使用示例
示例一 显示文件类型
[root@web ~]# file install.log
install.log: UTF-8 Unicode text
[root@web ~]# file -b install.log
UTF-8 Unicode text
[root@web ~]# file -i install.log
install.log: text/plain; charset=utf-8
[root@web ~]# file -b -i install.log
text/plain; charset=utf-8
[root@web ~]#
示例二 显示符号链接的文件类型
[root@rhel55 ~]# ls -l /var/mail
lrwxrwxrwx 1 root root 10 08-13 00:11 /var/mail -> spool/mail
[root@rhel55 ~]# file /var/mail
/var/mail: symbolic link to `spool/mail'
[root@rhel55 ~]# file -L /var/mail
/var/mail: directory
[root@rhel55 ~]# file /var/spool/mail
/var/spool/mail: directory
[root@rhel55 ~]# file -L /var/spool/mail
/var/spool/mail: directory
[root@rhel55 ~]#
示例三
[root@web186 root]# file *
1.sh: ASCII text
1.txt: empty
20080308xzmf.txt: ASCII text, with CRLF line terminators
448FD15874B0DC51.wav: RIFF (little-endian) data, WAVE audio, ITU G.711 a-law, mono 8000 Hz
449110BA327B23C6.vox: 8086 relocatable (Microsoft)
600d.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, stereo 44100 Hz
anaconda-ks.cfg: ASCII English text
banner.swf: data
commons-beanutils.jar: Zip archive data, at least v1.0 to extract
cvs_accept.sh: Bourne shell script text executable
data: directory
employer0605.txt: Non-ISO extended-ASCII text
GetFirstFile.class: compiled Java class data, version 49.0
GetFirstFile.java: ASCII Java program text
HELPFILE: C++ program text
httptunnel.zip: Zip archive data, at least v2.0 to extract
iptables_man.txt: ASCII English text, with overstriking
lnx61su_171.tar.gz: gzip compressed data, from Unix
megamgr.bin.filepart: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.0.0, statically linked, stripped
MegaPR_Linux_A02.tar.gz: gzip compressed data, was "MegaPR_Linux_A02.tar", from Win/32
mess0429.txt: ISO-8859 text, with very long lines
smartmontools-5.36.tar.gz: gzip compressed data, from Unix, max compression
sms.qunfa: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.2.5, dynamically linked (uses shared libs), not stripped
sms.vip.cfg: ISO-8859 text, with very long lines
top.txt: ASCII text, with CRLF, LF line terminators
voice20061128.rar: RAR archive data
vox2amr.sh: Bourne-Again shell script text executable
[root@web186 root]#
注：使用file命令显示出来的文件类型有些情况下不一定太准确，如上面黑体显示的.vox文件格式，应该是Dialogic VOX File格式的。
问题思考
1. 怎样自定义某种文件类型？
相关资料
【1】脚本学习 linux file命令: 辨别文件类型