[Hint] AWK One-Liners

Very helpful to manipulate text files quickly. I don't know much, but this little list of one-liners makes things pretty clear for some basic tasks.

A Handful of Useful awk One-Liners

Although awk can be used to write programs of some complexity, many useful programs are not complicated. Here is a collection of short programs that you might find handy and/or instructive. To run the program from the command line, on a single file named "filename", type: awk 'program' filename where program is the text in the following examples.

1. Print the total numnber of input lines:
   
   
   

   END { print NR }

   
   
2. Print the tenth input line:
   
   
   

   NR == 10



3. Print the last field of every input line:
   
   

   { print $NF }

   
   
4. Print the last field of the last input line:
   
   
   

   { field = $NF}
   END { print field }

   
   
5. Print every input line with more than 4 fields:
   
   
   

   NF > 4

   
   
6. Print every input line in which the last field is more than 4:
   
   
   

   $NF > 4

   
   
7. Print the total number of fields in all input lines:
   
   
   

   { nf = nf + NF }
   END { print nf }

   
   
8. Print the total number of lines that contain Beth:
   
   

   /Beth/ { nlines = nlines + 1 }
   END { print nlines }

   
   


9. Print the largest first fields and the line that contains it ( assumes some $1 is positive):
   
   
   

   
   

   
   

   $1 > max { max = $1 ; maxlines = $0 }
   END { print max, maxline)

   
   

   
   
   

   
   


10. Print every line that has at least one field:
    
    
    

    
    

    
    

    NF > 0

    
    

    
    
    

    
    


11. Pritn every line longer than 80 characters:
    
    
    

    
    

    
    

    length($0) > 80

    
    

    
    
    

    
    


12. Print the numer of fields in every line, followed by the line itself:
    
    
    

    
    

    
    

    { print NF, $0 }

    
    

    
    
    

    
    


13. Print the first two fields, in opposite order, of every line:
    
    
    

    
    

    
    

    { print $2, $1 }

    
    

    
    
    

    
    


14. Exchange the first two fields of every line and then print the line:
    
    
    

    
    

    
    

    { temp = $1 ; $1 = $2 ; $2 = temp ; print }

    
    

    
    
    

    
    


15. Print every line witg rge first field replaced by the line number:
    
    
    

    
    

    
    

    { $1 = NR ; print }

    
    

    
    
    

    
    


16. Print every line after erasing the second field:
    
    
    

    
    

    
    

    { $2 = ""; print }

    
    

    
    
    

    
    


17. Print in reverse order the fields of every line:
    
    
    

    
    

    
    

    { for (i=NF ; i>0 ; i=i-1) printf( "%s ", $i)
           printf("n")
    }

    
    

    
    
    

    
    


18. Print the sums of the fields of every line:
    
    
    

    
    

    
    

    { sum = 0
           for ( i=1 ; i<=NF ; i=i+1) sum = sum + $i
           print sum
    }

    
    

    
    
    

    
    


19. Add up all fields in all lines and print the sum:
    
    
    

    
    

    
    

    { for ( i=1 ; i<=NF ; i=i+1 ) sum = sum + $i}
    END { print sum }

    
    

    
    
    

    
    


20. Print every line after replacing each field by its absolute value:
    
    
    

    
    

    
    

    { for (i=1 ; i<=NF ; i=i+1) if ($i<0) $i=-$i
           print
    }

    
    

    
    
    

    
    

Source: The AWK Programming Language

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