awk

[ninonk-ncs]

awk '<filter> { <action> }' <input_file> awk '/pattern/ { print $0 }' file

Set field separator(FS) as

• - : awk -F '-' ...
• TAB : awk -F '\t' ...
• SPACE : awk -F ' ' ...

Filter

awk '/FOO BAR/' - filters lines that has 'FOO BAR'

pattern { action }

Examples (from man awk)

• Print lines longer than 72 characters. length($0) > 72
• Print first two fields in opposite order { print $2, $1 }
• Same, with input fields separated by comma and/or spaces and tabs

  BEGIN { FS = ",[ \t]*|[ \t]+"}
    { print $2, $1 }

• Add up first column, print sum and average.

  { s += $1 }
  END { print "sum is", s, " average is", s/NR }

• Print all lines between start/stop pairs /start/, /stop/

[ninonk-ncs]

Built in functions

reference

gsub(r,s) substitutes s for r globally in current input line, returns the number of substitutions gsub(r,s,t) substitutes s for r in t globally, returns number of substitutions index(s,t) returns position of string t in s, 0 if not present length(s) returns length of s match(s,r) returns position in s where r occurs, 0 if not present split(s,a) splits s into array a on FS, returns number of fields split(s,a,r) splits s into array a on r, returns number of fields sprintf(fmt, expr-list) returns expr-list formatted according to format string specified by fmt sub(r,s) substitutes s for first r in current input line, returns number of substitutions sub(r,s,t) substitutes s for first r in t, returns number of substitutions substr(s,p) returns suffix s starting at position p substr(s,p,n) returns substring of s length n starting at position p

[ninonk-ncs]

ls -lh | awk '{ printf "%-20s %s \n", $9, $5 }'

• ls -lh : list files with file size
• %-20s: add 20 char padding
• \n : because printf will not add new line

Output in ~

Applications         96B 
Desktop              704B 
Developer            512B 
Documents            2.9K 
Downloads            10K 
Library              2.8K 
Movies               224B 
Music                160B 
Personal             1.2K 
Pictures             192B 
Postman              96B 
Public               128B 
Workspace            608B 
big.log              87K 
iCloud               192B 
iCloud               192B 
iCloud               160B 
opt                  96B 
source               128B 

[ninonk-ncs]

Remove duplicate lines (stackoverflow) awk '!x[$0]++'

[ninokierulf]

Prefix with number for non blank lines (reference) awk 'NF { $0=++a " :" $0 }; { print }'