grep: Keeping lines that has specific string in certain column - awk

Question

I am trying to pick out the lines that have certain value in certain column and save it to an output. I am trying to do this with grep. Is it possible?
My data is looks like this:
apple 5 abcdefd ewdsf
peach 5 ewtdsfe wtesdf
melon 1 ewtedf wersdf
orange 3 qqqwetr hredfg
I want to pick out lines that have value 5 on its 2nd column and save it to new outputfile.
apple 5 abcdefd ewdsf
peach 5 ewtdsfe wtesdf
I would appreciate for help!

Answer 1

It is probably possible with grep but the adequate tool to perform this operation is definitely awk. You can filter every line having 5 on the second column with
awk '$2 == 5'
Explanation
awk splits it inputs in records (usually a line) and fields (usually a column) and perform actions on records matching certain conditions. Here
awk '$2 == 5'
is a short form for
awk '$2 == 5 {print($0)}'
which translates to
For each record, if the second field ($2) is 5, print the full record ($0).
Variations
If you need to choose dynamically the key value used to filter your values, use the -v option of awk:
awk -v "key=5" '$2 == key {print($0)}'
If you need to keep the first line of the file because it contains a header to the table, use the NR variable that keeps track of the ordinal number of the current record:
awk 'NR == 1 || $2 == 5'
The field separator is a regular expression defining which text separates columns, it can be modified with the -F field. For instance, if your data were in a basic CSV file, the filter would be
awk -F", *" '$2 == 5'
Visit the awk tag wiki to find a few useful information to get started learning awk.

Answer 2

To print when the second field is 5 use: awk '$2==5' file

Answer 3

Give this a try:
grep '^[^\s]\+\s5.*$' file.txt
the pattern looks for start of line, followed by more than one non-space character, followed by space, followed by 5, follwed by any number of chars, followed by eol.

Answer 4

You can get following command.
$ cat data.txt
apple 5 abcdefd ewdsf
peach 5 ewtdsfe wtesdf
melon 1 ewtedf wersdf
orange 3 qqqwetr hredfg
grape 55 kkkkkkk aaaaaa
$ grep -E '[^ ]+ +5 .*' data.txt > output.txt
$ cat output.txt
apple 5 abcdefd ewdsf
peach 5 ewtdsfe wtesdf
You can get the answer only with grep command.
But I strongly recommend you use awk command.

Answer 5

The simple way to do it is:
grep '5' MyDataFile
The result:
apple 5 abcdefd ewdsf
peach 5 ewtdsfe wtesdf
To capture that in a new file:
grep '5' MyDataFile > newfile
Note: that will find a 5 anywhere in MyDataFile. To restrict to the second column, a short script is what would suit your needs. If you want to limit it to the second column only, then a quick script like the following will do. Usage: script number datafile:
#!/bin/bash
while read -r fruit num stuff || [ -n "$stuff" ]; do
[ "$num" -eq "$1" ] && printf "%s %s %s\n" "$fruit" "$num" "$stuff"
done <"$2"
output:
$ ./fruit.sh 5 dat/mydata.dat
apple 5 abcdefd ewdsf
peach 5 ewtdsfe wtesdf