Many times I'll want to inspect a file and because I'm a DBA, my first inclination is to load the file into a database table so that I can write SQL queries against it. However, it's not always possible or timely to load the data into a database server to inspect a file. I've put together some useful grep commands below that I run to get a sense of the data attributes about the file.
For pretend purposes, let say we have a file named Person.csv that contains records about people. The file contains an Id, FirstName, LastName, DateRecordCreated and DateRecordUpdated columns. See below.
To count the number of instances of "2021" in a file.
$ grep -c -i 2021 Person.csv
Output:
4
To search for the existence of a pattern in a file
$ grep -i '2021' Person.csv
Output:
1,Bart,Simpson,1990-01-01,2021-01-01
3,Seth,Rogen,2000-07-01,2021-04-30
6,Bill,Gates,1966-05-04,2021-05-01
8,Drew,Brees,1999-02-15,2021-02-01
To obtain the line number(s) of a pattern in a file
$ grep -n -i 2021 Person.csv
Output:
2:1,Bart,Simpson,1990-01-01,2021-01-01
4:3,Seth,Rogen,2000-07-01,2021-04-30
7:6,Bill,Gates,1966-05-04,2021-05-01
9:8,Drew,Brees,1999-02-15,2021-02-01
To count the number of non pattern matches
$ grep -v -c 2021 Person.csv
Output:
6
Count number of instances of multiple pattern
$ grep -ioh "2018\|2019\|2020\|2021" Person.csv | sort | uniq -c | sort -n
Output:
1 2020
2 2019
4 2021
Count number of lines in a file
$ grep -c ^ Person.csv
Output:
10
