How to do a if else match on pattern in awk - shell

Question

I've tried the below command:
awk '/search-pattern/ {print $1}'
How do I write the else part for the above command?

Answer 1

Classic way:
awk '{if ($0 ~ /pattern/) {then_actions} else {else_actions}}' file
$0 represents the whole input record.
Another idiomatic way
based on the ternary operator syntax selector ? if-true-exp : if-false-exp
awk '{print ($0 ~ /pattern/)?text_for_true:text_for_false}'
awk '{x == y ? a[i++] : b[i++]}'
awk '{print ($0 ~ /two/)?NR "yes":NR "No"}' <<<$'one two\nthree four\nfive six\nseven two'
1yes
2No
3No
4yes

Answer 2

A straightforward method is,
/REGEX/ {action-if-matches...}
! /REGEX/ {action-if-does-not-match}
Here's a simple example,
$ cat test.txt
123
456
$ awk '/123/{print "O",$0} !/123/{print "X",$0}' test.txt
O 123
X 456
Equivalent to the above, but without violating the DRY principle:
awk '/123/{print "O",$0}{print "X",$0}' test.txt
This is functionally equivalent to awk '/123/{print "O",$0} !/123/{print "X",$0}' test.txt

Answer 3

Depending what you want to do in the else part and other things about your script, choose between these options:
awk '/regexp/{print "true"; next} {print "false"}'
awk '{if (/regexp/) {print "true"} else {print "false"}}'
awk '{print (/regexp/ ? "true" : "false")}'

Answer 4

The default action of awk is to print a line. You're encouraged to use more idiomatic awk
awk '/pattern/' filename
#prints all lines that contain the pattern.
awk '!/pattern/' filename
#prints all lines that do not contain the pattern.
# If you find if(condition){}else{} an overkill to use
awk '/pattern/{print "yes";next}{print "no"}' filename
# Same as if(pattern){print "yes"}else{print "no"}

Answer 5

This command will check whether the values in the $1 $2 and $7-th column are greater than 1, 2, and 5.
!IF! the values do not mach they will be ignored by the filter we declared in awk.
(You can use logical Operators and = "&&"; or= "||".)
awk '($1 > 1) && ($2 > 1) && ($7 > 5)'
You can monitoring your system with the "vmstat 3" command, where "3" means a 3 second delay between the new values
vmstat 3 | awk '($1 > 1) && ($2 > 1) && ($7 > 5)'
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