Linux命令学习总结: file命令

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 ...

命令参数：

下表列出了部分常用的参数。

使用示例：

1：查看file命令的帮助信息

[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：查看文件类型

例如，如下所示，Temp.txt 文件类型为text，编码为UTF-8 Unicode

[root@DB-Server ~]# file Temp.txt 

Temp.txt: UTF-8 Unicode text, with very long lines, with CRLF line terminators

3：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。

[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.txt

UTF-8 Unicode text, with very long lines, with CRLF line terminators

4: 输出mime类型的字符串

[root@DB-Server ~]# file -i Temp.txt 

Temp.txt: text/plain; charset=utf-8

5: 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。

[root@DB-Server ~]# cat >test

/root/install.log 

it is only one test file

[2]+  Stopped                 cat > test

[root@DB-Server ~]# file -f  test

/root/install.log:        ASCII text

it is only one test file: ERROR: cannot open `it is only one test file' (No such file or directory)

[root@DB-Server ~]# 

[root@DB-Server ~]# 

5: 使用指定分隔符号替换输出文件名后的默认的“：”分隔符。

感觉这个参数很鸡肋！我搞明白这个参数的作用时，很是纳闷。

6：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 ~]# 

7： 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 ~]#