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I have a file named test which has two columns one having ID and other having status.

I want to loop through the file and print IDs where status have one particular value (e.g. 'ACTIVE').

I tried
cat test | while read line; do templine= $($line | cut -d ' ' -f 2);echo $templine; if [ $templine = 'ACCEPTED' ]; then echo "$templine"; fi done and some variation of above which obviously did not work.

Any help would be appreciated.

Abhijeet Shukla
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  • cat test | while read line; do templine= $($line | cut -d ' ' -f 2);echo $templine; if [[ $templine = 'ACCEPTED' ]]; then echo "$templine"; fi done

    above command treadted IDs as commands and started executing them

     – Abhijeet Shukla Feb 22 '16 at 09:36
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    Have you considered just grepping the lines and then getting the column of the IDs only? – FelixJN Feb 22 '16 at 09:39
  • egrep "[^[:space:]]*[:space:]ACTIVE" | awk ' { print $1 } ' – Rui F Ribeiro Feb 22 '16 at 09:44
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    @RuiFRibeiro that would be awk '$2 == "ACTIVE" { print $1 }' ;-) – Stephen Kitt Feb 22 '16 at 09:50
  • Even better and more compact, I never remember to use awk´s BEGIN block. Thanks! – Rui F Ribeiro Feb 22 '16 at 09:52
  • @StephenKitt worked like a charm! Thanks, I am a newbie with Unix and was struggling with this for quite some time now.

    any idea why my query above did not work ?

     – Abhijeet Shukla Feb 22 '16 at 09:54
  • your query didn't work because you had just templine=$($line | cut ...) rather than $(echo "$line" | cut ...) or, better yet: $(printf '%s' "$line" | cut ...). your version of the command attempted to execute the command contained in $line - which almost certainly doesn't exist. you probably also wanted cat test | while IFS= read line ; do ... so that read assigns the entire input line to $line rather than just the first field. but as has been mentioned awk is a better tool for this job. – cas Feb 22 '16 at 10:00
  • See also Why is using a shell loop to process text considered bad practice? – Stéphane Chazelas Feb 22 '16 at 10:45
  • @cas : Thanks for your suggestion cat test | while read line; do templine= $(echo "$line" | cut -f 2) ; done; I made the changes as suggested but now it's executing the command contained in templine – Abhijeet Shukla Feb 22 '16 at 10:49

2 Answers2

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When you need to manipulate data in fields, awk tends to fit the bill quite nicely:

awk '$2 == "ACTIVE" { print $1 }' test

This reads each line of test, splits it into fields, then checks if the second one ($2) is ACTIVE; if so, it prints the first field.

Stephen Kitt
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  • another variation, if you want a regexp search on field 2 rather than an exact match, is: awk '$2 ~ /ACTIVE/ { print $1 }' – cas Feb 22 '16 at 09:55
  • @StephenKitt worked like a charm! Thanks, I am a newbie with Unix and was struggling with this for quite some time now. any idea why my query above did not work ? – Abhijeet Shukla Feb 22 '16 at 09:55
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    @AbhijeetShukla, the main problem in your attempt is templine= $($line | cut -d ' ' -f 2), which runs $line; to fix that, echo $line instead, and remove the space after the =: templine=$(echo $line | cut -d ' ' -f 2). If you want to use read you can use that to split the input into fields: while read id status; do if [ "$status" = "ACTIVE" ]; then ...; fi; do. – Stephen Kitt Feb 22 '16 at 09:58
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see below example i hope its helpful for you 

g=7

echo $g

output: 7

h=`echo $g`

echo $h

i hope its helpful for you see below image

enter image description here

Tiger
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