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awk

an awk-ward (or not really) language.

some notes in process.

resources

$0 represents the entire input record, and $n the nth field in the current record

the index of the first character is 1!

index( string, sub) : index of sub as a substring of string
length( string )
match( string, regex ) : index of the longest match of regex in string
split( string, arr, regex ) : split string into array using regex as separato
printf( format, expr-list)
strtonum(string): useful to convert from hexadecimal (0x prefix) or octal (0 prefix)
gsub( regex, sub, string): global substitution of regex with sub in string. if string is ommited, $0 is used
sub(regex, sub, string): substitute regex with sub in string, once. if string is omitted, $0 is used
substr(string, start, len): returns the substring from start index, with length len. if len is ommitted, it goes until the end of the string
tolower( str )
toupper( str )

note: to run in compatibility mode, without gnu extensions, use the -c or --traditional flag:

$ awk -c

records separated by empty lines can be extracted with:

RS = ""

without modifying FS, fields will be separated by any whitespace, including newlines.

gawk allows regexp in RS, traditional awk will only accept one character.

arr["a"] = 1
arr["b"] = 2

for(key in arr)
  print key ": " arr[key]

most recent update on: 12021-12-01