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http://michaels.blogbus.com/logs/44427299.html

In our work, we often encounter the following questions:
在我们的工作中，我经常遇到下面的问题：
I have two files: file1 and file2:
有两个文件：文件1和文件2：
1) How can I print out the lines that are only contained in file1?
1) 如何打印出只存在于文件1中的内容？
2) How can I print out the lines that are only contained in file2?
2) 如何打印出只存在于文件2中的内容？
3) How can I print out the lines that are contained both in file1 and file2?
3) 如何打印出文件1和文件2都有的内容？

There is a powerful shell command that can easily meet our needs, it is: comm.
这有一个很好的shell命令能够满足我们的需求，它就是comm。

When you meet the above questions, "comm" should be your first choice:-)
当你遇到上面的问题，“comm”应该是你第一选择:-)

comm [ -123 ]??file1??file2

comm will read file1 and file2 and generate three columns of output:
comm 将会读取文件1和文件2并且产生三列输出：
lines only in file1; lines only??in file2; and lines in both files.
只存在文件1中的行；只存在文件2中的行；两个文件都存在的行。
For detailed explanation, pls man comm.
更详细的解释，请参阅man comm。

Example:
例如：

bash-2.03$ cat file1
11111111
22222222
33333333
44444444
55555555
66666666
77777777
88888888
99999999
bash-2.03$ cat file2
00000000
22222222
44444444
66666666
88888888

1) suppress lines unique to FILE1
1) 过滤掉file1中的内容
bash-2.03$ comm -1 file1 file2
00000000
        22222222
        44444444
        66666666
        88888888

2) suppress lines unique to FILE2
2) 过滤掉file2中的内容
bash-2.03$ comm -2 file1 file2
11111111
        22222222
33333333
        44444444
55555555
        66666666
77777777
        88888888
99999999

3) suppress lines that appear in both files
3) 过滤掉file1和file2中都有的内容
bash-2.03$ comm -3 file1 file2
        00000000
11111111
33333333
55555555
77777777
99999999

4) Print out the lines that are only contained in file1?
4) 打印出只存在于文件1中的内容？
bash-2.03$ comm -23 file1 file2
11111111
33333333
55555555
77777777
99999999

5) Print out the lines that are only contained in file2?
5) 打印出只存在于文件2中的内容？
bash-2.03$ comm -13 file1 file2
00000000

6) Print out the lines that are contained both in file1 and file2?
6) 打印出文件1和文件2都有的内容？
bash-2.03$ comm -12 file1 file2
22222222
44444444
66666666
88888888

Besides the comm, we still have various ways to finish the above tasks.
除了comm，我们还有其他方法来完成这些任务。

4) Print out the lines that are only contained in file1?
4) 打印出只存在于文件1中的内容？
diff file1 file2 | grep "^<"|sed 's/^< //g'
for i in $(<file1); do (grep $i file2)||echo $i>>temp ; done;
cat temp

In comparison, comm is much easier to remember. :-)
相比之下，comm更加便于记忆。

转自：http://hi.baidu.com/will_hu/blog/item/4b05fedf0276fd5fcdbf1a6d.html