在两个文件之间查找属性中的增量

Question

This is primarily an approach/concept question, and I appreciate any input you might have.

The problem: I often need to compare and edit a property file, and in doing so I'm mainly interested to find new properties that exist in the new file compared to the old one. To achieve this I often employ diff old_file.prop new_file.prop ,but due to the high number of lines/properties in each file (~150) this method isn't efficient and is error prone.

Sample old_file.prop :

name.host=mycomputer1
internal.port=21
external.gateway=sample.my.machine

Sample new_file.prop :

name.host=change_me
internal.port=21
external.gateway=change_me
external.port=501

Here diff command will return:

<name.host=mycomputer1
<external.gateway=sample.my.machine
>name.host=change_me
>externa.gateway=change_me
>external.port=501

The only output of interest/desired in this example is external.port and not the value it holds (and perhaps a line number as well). I'm a bit familiar with sed , but I don't think it can do this without prior knowledge of the properties in the new file.

Is there a way to efficiently achieve this using bash script?

Thank you,

Answer 1

Code for GNU awk :

awk -F= 'NR==FNR {a[$1]++;next}; !a[$1] {print $1, "line", FNR}' fileOld fileNew

Answer 2

As an alternative on @mob's answer, and to give some other possibilities:

1. To show properties that have been removed in new_file

   comm -23 <(cut -d= -f1 old_file) <(cut -d= -f1 new_file)

2. To show properties that have been added in new_file

   comm -13 <(cut -d= -f1 old_file) <(cut -d= -f1 new_file)

3. To show common properties in the two files

   comm -22 <(cut -d= -f1 old_file) <(cut -d= -f1 new_file)

Answer 3

You could use cut to ignore any input after the first = on each line:

diff <(cut -d= -f1 old_file) <(cut -d= -f1 new_file)

Projected output:

22a23
> external.port