Fetch values from particular file and display swapped values in terminal

Question

I have a file named input.txt which contains students data in StudentName|Class|SchoolName format.

Shriii|Fourth|ADCET
Chaitraliii|Fourth|ADCET
Shubhangi|Fourth|ADCET
Prathamesh|Third|RIT

I want to display this values in reverse order for particular college. Example:

ADCET|Fourth|Shriii
ADCET|Fourth|Chaitraliii

I used grep 'ADCET$' input.txt which gives output

Shriii|Fourth|ADCET
Chaitraliii|Fourth|ADCET

But I want it in reverse order. I also used grep 'ADCET$' input.txt | sort -r but didn't get required output

Maybe see this: https://stackoverflow.com/a/13367179/1970049 for a function to reverse comma-separeted values (you can customize your separator via regexp). — krassdanke, Feb 21 '19 at 09:55
@WiktorStribiżew `grep 'ADCET$' input.txt | tac` swapped it vertically. That's not the expected output. — SMshrimant, Feb 21 '19 at 09:59
@dth The input.txt file contains `|` separated values and not `,` separated values. — SMshrimant, Feb 21 '19 at 10:00
@WiktorStribiżew It worked. Can you give detailed explanation so that I can mark it as the correct answer. — SMshrimant, Feb 21 '19 at 10:07
Added all the explanations to the answer, glad it worked for you. — Wiktor Stribiżew, Feb 21 '19 at 10:20

Wiktor Stribiżew · Accepted Answer · 2019-02-21T10:19:38.323

You may use either of the following sed or awk solutions:

grep 'ADCET$' input.txt | sed 's/^\([^|]*\)\(|.*|\)\([^|]*\)$/\3\2\1/'
grep 'ADCET$' input.txt | awk 'BEGIN {OFS=FS="|"} {temp=$NF;$NF=$1;$1=temp;}1'

awk details

BEGIN {OFS=FS="|"} - the field separator is set to | and the same char will be used for output
{temp=$NF;$NF=$1;$1=temp;}1:
- temp=$NF; - the last field value is assigned to a temp variable
- $NF=$1; - the last field is set to Field 1 value
- $1=temp; - the value of Field 1 is set to temp
1 - makes the awk write the output.

sed details

The \3\2\1 are placeholders for values captured into Groups 1, 2 and 3.

1 Answers1