背景

   學習如何比較2個檔案不同，便於在ORACLE分析資料塊變更時用上此功能。

結論

1,diff用於比較2個檔案的不同
2,diff用於比較2個檔案的內容，顯示結果如下 
1c1
< mynewly
---
> my
上述具體含義請見下述測試


3,  
變化標記有3種情況，各為
c  --即變化，即記錄發生了變化
a  --即增加了記錄
d  --即刪除了記錄

測試

1,建立2個相同檔案
[root@seconary test_diff]# more file1.txt 
a
b
c
[root@seconary test_diff]# 
[root@seconary test_diff]# more file2.txt 
a
b
c
[root@seconary test_diff]# 


2，比較2個相同的檔案
如果2個檔案相同，不顯示任何資訊
[root@seconary test_diff]# diff file1.txt file2.txt 
[root@seconary test_diff]# 




3，比較2個檔案，且右檔案發生變化
修改file2.txt
[root@seconary test_diff]# more file2.txt 
anewly
b
c
[root@seconary test_diff]# 


僅1個檔案變化，diff結果顯示
[root@seconary test_diff]# diff file1.txt file2.txt 
1c1
< a  ---這個表示第個檔案的發生變化的哪一行的開頭的字母，顯示形式為 < a
---
> anewly --這個表示發生變化的檔案的變化後的記錄


再次修改file2.txt
[root@seconary test_diff]# more file2.txt 
anewly
b
cnewly2


比較2個檔案，如果發生變化檔案的有多條記錄，會把發生變化的多條記錄也顯示出來
[root@seconary test_diff]# diff file1.txt file2.txt 
1c1
< a
---
> anewly
3c3
< c
---
> cnewly2


4，比較2個檔案，左檔案發生變化
刪除file2.txt，繼續測試
[root@seconary test_diff]# rm -rf file2.txt 
[root@seconary test_diff]# 


[root@seconary test_diff]# cp file1.txt file2.txt
[root@seconary test_diff]# 


修改file1.txt
[root@seconary test_diff]# more file1.txt 
a
bnewly
c


比較2個檔案
[root@seconary test_diff]# diff file1.txt file2.txt
2c2
< bnewly --發生變化的檔案，修改後的內容
---
> b   --發生變化的檔案，發生變化前的記行錄


再次修改file1.txt
[root@seconary test_diff]# more file1.txt
asb
bnewly
c


比較2個檔案
[root@seconary test_diff]# diff file1.txt file2.txt
1,2c1,2
< asb
< bnewly
---
> a
> b


刪除2個比較檔案，繼續測試，採用單條記錄多字元方式（上面測試皆採用單記錄單字元）
[root@seconary test_diff]# rm file*
rm: remove regular file `file1.txt'? y
rm: remove regular file `file2.txt'? y
[root@seconary test_diff]# 




[root@seconary test_diff]# more file1.txt
my
birthday
is
[root@seconary test_diff]# more file2.txt 
my
birthday
is
[root@seconary test_diff]# 


修改左檔案file1.txt
[root@seconary test_diff]# more file1.txt
mynewly
birthday
is


比較2個檔案，
[root@seconary test_diff]# diff file1.txt file2.txt
1c1 --分為3個部分，1表示左檔案第1行記錄，c表示是改變，1表示左檔案的第1條記錄變成左檔案第1條記錄
< mynewly --分為2個部分，變化後的行內容
---  --表示左檔案和右檔案
> my  --分為2個部分，變化前的行內容


修改左檔案
[root@seconary test_diff]# more file1.txt
mynewly
birthday
isthird


比較2個檔案
[root@seconary test_diff]# diff file1.txt file2.txt
1c1
< mynewly
---
> my
3c3
< isthird
---
> is


測試下左檔案新增記錄,即刪除deletion
[root@seconary test_diff]# more file1.txt
col1
col2
col3
[root@seconary test_diff]# 
[root@seconary test_diff]# more file2.txt
col1
col2
col3
[root@seconary test_diff]#


[root@seconary test_diff]# more file1.txt
col1
col2
col3
newaddrecord
[root@seconary test_diff]# 


[root@seconary test_diff]# diff file1.txt file2.txt
4d3
< newaddrecord
[root@seconary test_diff]# 


測試下左檔案刪除記錄,可見變化標識為a,即增加addition
[root@seconary test_diff]# more file1.txt
col1
col3
[root@seconary test_diff]# 


[root@seconary test_diff]# diff file1.txt file2.txt
1a2
> col2
[root@seconary test_diff]# 

參考資料

http://blog.chinaunix.net/uid-26000296-id-3507646.html

個人簡介：