最後更新: 2022-02-08

目錄

• comm
• cmp
• diff
• patch

---

comm

 

Compare sorted files FILE1 and FILE2 line by line.

With no options, produce three-column output.

column

unique to FILE1 | unique to FILE2 | common to both files

Opt

       -1     suppress column 1 (lines unique to FILE1)
       -2     suppress column 2 (lines unique to FILE2)
       -3     suppress column 3 (lines that appear in both files)

Example    

       -12    Print only lines present in both file1 and file2 (即係得返 3)
       -23    Print lines in file1 not in file2 (得返 1)

Example

cat a.txt

1
2
3
4

cat b.txt

3
4
5
6

comm a.txt b.txt

1
2
                3
                4
        5
        6

 

---

cmp

 

compare two files byte by byte

cmp a.txt b.txt

a.txt b.txt differ: byte 1, line 1

Opts

-b  --print-bytes              # Print differing bytes.

cmp -b a.txt b.txt

a.txt b.txt differ: byte 1, line 1 is  61 1  63 3

-i SKIP  --ignore-initial=SKIP              Skip the first SKIP bytes of input.

-i SKIP1:SKIP2                                  Skip the first SKIP1 bytes of FILE1 and the first SKIP2 bytes of FILE2.

 

---

diff

 

介紹

diff comparing the files line by line.

Unlike CLI "cmp" and "comm", it instructions(建立 change-command) that are required to make two files identical.

Usage

old.txt

a
b
c
d

new.txt

d
e
f
g

diff old.txt new.txt > patch.txt

cat patch.txt

1,3d0
< a
< b
< c
4a2,4
> e
> f
> g

change-command

[1]

1,3d0

1. line numbers (ie. 4a) / range(ie. 1,3d) in the first file
2. Special symbols are: (a: add c: change d: delete)
3. line numbers / range corresponding to the second file match

old.txt 的第一至第三行刪除後就會 match new.txt 的 0 行 (0=開始)

< a
< b
< c

• < removed from file
• > added to the file

在 old.txt 分別刪除 a, b, c

[2]

4a2,4
> e
> f
> g

在 old.txt 原本的第4行後加上 e, f, g 去 match new.txt 的 第 2~4 行.

Useful Opts

-b, --ignore-space-change   # ignore changes in the amount of white space

-B, --ignore-blank-lines       # ignore changes where lines are all blank

-i  --ignore-case

-q                                     # Output only whether files differ.

-r                                     # Recursively compare any subdirectories found.

 

Exit status

• 0 means no differences were found
• 1 means some differences were found
• 2 means trouble

Unified mode(-u)

The default output of diff intended to be read by a computer, not a human

Unified mode for human purposes

diff -u old.txt new.txt

--- old.txt     2022-02-08 12:25:31.559076225 +0800
+++ new.txt     2022-02-08 12:25:41.447038776 +0800
@@ -1,4 +1,4 @@
-a
-b
-c
 d
+e
+f
+g

Example: 對比目錄的不同

方法 1

diff -r dir1 dir2 | grep dir1 | awk '{print $4}' > difference1.txt

• -q      # Output only whether files differ.
• -r      # Recursively compare any subdirectories found.

另外方法

Use find to list all the files in the directory then calculate the md5 hash for each file and pipe it to a file:

# cd /root/dir1

find public_html/ -type f -exec md5sum '{}' \; > /root/old.txt

# go to another folder ( cd /root/dir2 )

find public_html/ -type f -exec md5sum '{}' \; > /root/new.txt

# cd /root

diff old.txt new.txt

 

---

patch

 

apply a diff file to an original

patch [options] [originalfile [patchfile]]

option

• -b, --backup
• -c (--context), -e (--ed), -n (--normal)      # patch attempts to determine the type of the diff listing
• --binary                                                  #  patches should be generated by diff --binary
• --dry-run
• -R, --reverse                                           # patch attempts to swap each hunk around before applying it.

Usage

patch old.txt patch.txt

patching file old.txt