Standard Unix/Linux utility for testing every input line

Question

I am writing a Bash script which should test if every line in input meet certain condition.

Is there a way to take the predicate and reduce all the line to either 0 or 1 so I don't have to code the looping code myself using a utility that is routinely standard or readily available in Linux distributions?

Answer 1

Sample data (we want all lines that contain "want"):

$ cat x
not this
want this
not that
want that

---

You coud use awk:

• Print a 1 if the line matches regex /want/
• Print a 0 if the line does not match

$ cat x | awk '{if(match($0,/want/)){print 1}else{print 0}}'
0
1
0
1

---

Or try sed:

• Replace lines that contain just 1 with 0 (otherwise they will pass through as a 1)
• Replace lines containing "want" with a 1
• Replace lines that are not a 1 with a 0

$ cat x | sed -re 's/^1$/0/' -e 's/^.*want.*$/1/' -e 's/^[^1][^$].*$/0/'
0
1
0
1