Summary of common awk Information

1. regular Expression of awk metacharacters \ code sequences ^ start matching at the beginning of the string $ start matching at the end of the string. match any single string match any character in [ABC] and any character in [] Match [A-Ca-c] match the characters in the A-C and a-c range (in alphabetical order) [^ ABC] matches any character other than [] with Desk | Chair matches any one of Desk and Chair with [ABC] [DEF. Matches any character in A, B, and C, and must be followed by any character in D, E, and F. * Matches www.2cto.com + with any of the following 0 or multiple characters in A, B, or C: matching? Matches A null string or A, B, or C in any one character (Blue | Black) berry combines regular expressions to match Blueberry or Blackberry 2. usage of awk Arithmetic Operators ---------------- y Power x of x ^ y x ** y same as x % y to calculate the remainder of x/y (Modulo) x + y x plus yx-y x minus yx * y x multiplied by yx/y x except y-y Minus y (switch symbol of y ); it is also called a one-time subtraction ++ y plus 1 and then use y (pre-added) y ++ with the y value plus 1 (suffix added) -- y minus 1 and use y (minus) y -- use y minus 1 (minus suffix) x = y: Assign the value of y to xx + = y. Assign the value of x + y to xx-= y. Then, assign the value of x-y to xx * = y and then x * the value of y is assigned to xx/= y. The value of x/y is assigned to x % = y. The value of x % y is assigned to xx ^ = y. The value of x ^ y is assign xx ** = y the value of x ** y to x www.2cto.com 3. test allowed by awk: Operator meaning x = y x Equal to yx! = Y x is not equal to yx> y x is greater than yx> = y x is greater than or equal to yx <y x is less than yx <= y x is less than or equal to y? X ~ Re x matches the regular expression re? X !~ Re x does not match the regular expression re? 4. awk operators (sorted in ascending order of priority) =, + =,-=, * =,/=, % = ||&>>=<<==! = ~ !~ Xy (string link, 'x' y' to "xy") +-*/% + + -- 5. awk built-in variables (pre-defined variables) Description: item v in the table indicates the first tool that supports variables (the same below): A = awk, N = nawk, P = POSIX awk, G = gawk V variable meaning default value: Limit n argc command line parameter count g argind argv flag of the currently processed file n argv command line parameter array g convfmt number conversion format %. 6gP environ unix environment variable n errno unix system error message g fieldwidths input field width blank separator string a filename current input file name p fnr current record number www.2cto.com a fs input field separator space G IGNORECASE control case sensitivity 0 (Case sensitivity) A nf number of fields in the current record a nr number of records read a ofmt number output format %. 6gA OFS output field separator space a ors output record separator New Line a rs input record other delimiter new line n rstart matched function matched string first n rlength matched function matched String Length n subsep subscript separator "\ 034" 6. awk built-in function V function usage or return value ------------------------------------------------ N gsub (reg, string, target) replace stringN index (search, string) in target when the regular expression reg matches) returns the position A length (string) of the search string in the string to evaluate the number of characters in the string. N match (string, reg) returns the string matching the regular expression reg. Position N printf (format, variable) format output, output variable in the format provided by format. N split (string, store, delim) breaks down string into the store array element N sprintf (format, variable) according to the delim, and returns a formatted data containing the format, variables is the data G strftime (format, timestamp) to be put in the string to return a format-based date or time string. timestmp is the time N sub (reg, string, target) for the first time when the regular expression reg matches, replace the string A substr (string, position, len) in the target string to return A substring P totower (string) whose position starts with len) returns the lowercase P toupper (string) character in string. returns the cotangent (radian) www.2 of the uppercase character A atan (x, y) x in string. Cto.com N cos (x) x cosine (radian) A exp (x) e x power A int (x) x integer part A log (x) the natural logarithm of x to the sine (radian) A sqrt (x) x of the random number N sin (x) x between N rand () 0-1 A srand (x) initialize the random number generator. If x is ignored, system () G system () is used to return the time (in seconds) elapsed since January 1, January 1, 1970 by the author fengyv.