Find Longest Line in a File

awk ' { if ( length > x ) { x = length } }END{ print x }' file.txt

Perform Floating Point Calculations

awk can be used for complex calculations, for example:

awk 'BEGIN {printf "%.3f\n", sin(30 * atan2(0, -1)/180)}'

will calculate $\sin(30^\circ)=sin(30rad * \frac{\pi}{180})$ and return:

0.500

Since awk does not have a constant for $\pi$, we use atan2(0, -1) instead.

Delimiter-Style

Suppose you have a file input containing data separated by delimiters such as:

variable = value

or:

variable = value

The following command can be used to obtain value:

awk -F"[ \t]*[=][ \t]*" '{ print $2 }' input

Remove Duplicate Entries in File Without Sorting

To remove all duplicates from file.txt without sorting, issue:

awk '!x[$0]++' file.txt

Merge Lines by Two in File

Given a file with the contents:

Q: What is this?
A: This is a FAQ!

and you would like to achieve:

Q: What is this? A: This is a FAQ!

then the following awk one liner:

awk 'NR%2{printf "%s ",$0;next;}1' yourFile

will merge all the lines in a file by two.

Convert Key-Value Map to JSON

Given an input such as:

a1 : "abc
c2  : def
e3 : "ghi "
f5 :" a     b"

The following awk script:

awk -F: '
    function trim(s) { 
        return gensub(/^[ \t"]*|[ \t"]*$/, "", "g", s) 
    }
    BEGIN {
        printf "{"
    } 
    NR > 1 { 
        printf(", ") 
    } 
    { 
        printf("\"%s\":\"%s\"", trim($1), trim(substr($0, index($0,":") + 1)));
    }
    END {
        print "}"
    }
'

will return the JSON object:

{"a1":"abc","c2":"def","e3":"ghi","f5":"a     b"}

where keys and values are trimmed for spaces and quotes from the start and end.

One example application would be creating a JSON object out of the status of an APC UPS:

apcaccess | awk -F: '
    function trim(s) { 
        return gensub(/^[ \t"]*|[ \t"]*$/, "", "g", s) 
    }
    BEGIN {
        printf "{"
    } 
    NR > 1 { 
        printf(", ") 
    } 
    { 
        printf("\"%s\":\"%s\"", trim($1), trim(substr($0, index($0,":") + 1)));
    }
    END {
        print "}"
    }
'

fuss/awk.txt ยท Last modified: 2018/01/02 01:47 by office

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