如何在 UNIX 中比较两个 csv 文件并创建增量（修改/新记录）答案

【问题标题】：How to compare two csv files in UNIX and create delta ( modified/ new records )如何在 UNIX 中比较两个 csv 文件并创建增量（修改/新记录）
【发布时间】：2017-03-23 07:17:46
【问题描述】：

我有两个 csv 文件 old.csv 和 new.csv。我只需要 new.csv 文件中的新记录或更新记录。如果 old.csv 中存在记录，则从 new.csv 中删除记录。

old.csv

"R","abc","london","1234567"
"S","def","london","1234567"
"T","kevin","boston","9876"
"U","krish","canada","1234567"

new.csv

"R","abc","london","5678"
"S","def","london","1234567"
"T","kevin","boston","9876"
"V","Bell","tokyo","2222"

new.csv 中的输出

"R","abc","london","5678"     
"V","Bell","tokyo","2222"

注意：如果 new.csv 中的所有记录都相同，那么 new.csv 应该为空

【问题讨论】：

标签： unix awk

【解决方案1】：

例如使用grep:

$ grep -v -f old.csv new.csv # > the_new_new.csv 
"R","abc","london","5678"
"V","Bell","tokyo","2222"

和：

$ grep -v -f old.csv old.csv
$                            # see, no differencies in 2 identical files

man grep:

  -f FILE, --file=FILE
          Obtain  patterns  from  FILE,  one  per  line.   The  empty file
          contains zero patterns, and therefore matches nothing.   (-f  is
          specified by POSIX.)

  -v, --invert-match
          Invert the sense of matching, to select non-matching lines.  (-v
          is specified by POSIX.)

再一次，你可以使用 awk：

$ awk 'NR==FNR{a[$0];next} !($0 in a)' old.csv new.csv
"R","abc","london","5678"
"V","Bell","tokyo","2222"

解释：

awk '
NR==FNR{            # the records in the first file are hashed to memory
    a[$0]
    next
} 
!($0 in a)          # the records which are not found in the hash are printed
' old.csv new.csv   # > the_new_new.csv

【讨论】：

您的答案没有awk？奇怪:)，我也认为我们应该将其添加为awk Wiki FAQ 的一部分，一周中的每一天都有这样的问题！也许 Ed Morton 可以在这方面有发言权。
awk 解决方案要快得多。

【解决方案2】：

文件排序时：

comm -13 old.csv new.csv

当它们没有被排序，并且允许排序时：

comm -13 <(sort old.csv) <(sort new.csv)

【讨论】：