https://www.thegeekstuff.com/2010/01/awk-introduction-tutorial-7-awk-print-examples/

format:

`awk 'condition { action }' file

$ awk '{ print $1, $3 }' file.txt  # print columns 1 and 3

$ awk '/error/ { print }' logfile.txt 
# print only the lines (entire line) that contain "error"

prepend line numbers with 'NR' :
awk '{print NR, $4}' login.log

search within lines:

awk `/jimmy/`

sum a column:

awk '{sum += $5} END {print sum}' file.log

-F : defining custom separators, delimiters

specify custom field separators in awk using the -F option or by setting the FS variable.

Using -F flag (most common way):

# Split on colon
$ awk -F ':' '{print $1, $2}' logfile.txt

# Split on comma ( useful when parsing csv )
$ awk -F ',' '{print $1, $2}' logfile.txt

Using regular expressions as separators:

# Split on one or more colons
$ awk -F ':+' '{print $1, $2}' logfile.txt

# Split on either colon or semicolon
$ awk -F '[;:]' '{print $1, $2}' logfile.txt

# Split on colon followed by optional spaces
$ awk -F ': *' '{print $1, $2}' logfile.txt

Multiple separators - split on both whitespace AND colon:

awk -F '[ :]' '{print $1, $2, $3}' logfile.txt

Substitutions

using gsub Inside the awk script:

substitute ':nnnnn' gsub() = global substitution,

awk '{gsub(/:[0-9]{5}/, " PORT& "); print}' logfile.txt

• gsub = "global substitute" - replaces ALL occurrences in the line (unlike sub which only replaces the first)
• /:[0-9]{5}/ = the regex pattern to find (colon followed by exactly 5 digits)
• " PORT& " = the replacement string
  • PORT = literal text "PORT"
  • & = special symbol that represents the matched text (so :50888 becomes PORT:50888)
  • The spaces around it create separation in the output
• The semicolon ; separates this statement from the next

print - Prints the modified line (after gsub has made the replacements)

inserting text into columns

awk '{print $3 "->" $5}' modbus.log > ip_pairs.txt
prints col3 -> col5 and saves to ip_pairs.txt