简单shell 脚本就是看不懂，晕。

wuxiaobo_2009

1. #!/bin/sh
   
2. # grep3 - prints out three lines around pattern
   
3. # if there is only one argument, exit
   
4. 
   
5. case $# in
   
6.         1);;
   
7.         *) echo "Usage: $0 pattern";exit;;
   
8. esac;
   
9. # I hope the argument doesn't contain a /
   
10. # if it does, sed will complain
    
11. 
    
12. # use sed -n to disable printing
    
13. # unless we ask for it
    
14. sed -n '
    
15. '/$1/' !{
    
16.         #no match - put the current line in the hold buffer
    
17.         x
    
18.         # delete the old one, which is
    
19.         # now in the pattern buffer
    
20.         d
    
21. }
    
22. '/$1/' {
    
23.         # a match - get last line
    
24.         x
    
25.         # print it
    
26.         p
    
27.         # get the original line back
    
28.         x
    
29.         # print it
    
30.         p
    
31.         # get the next line
    
32.         n
    
33.         # print it
    
34.         p
    
35.         # now add three dashes as a marker
    
36.         a\
    
37. ---
    
38.         # now put this line into the hold buffer
    
39.         x
    
40. }

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'

前边的case 就是bug 呀。后边的sed 没有理解。

waker

grep -C3