1.awk Regular expression meta-character
\ code-changing sequence
^ Start match at beginning of string
$ start match at end of string
. Match any single string
[ABC] matches any character within []
[A-ca-c] matches characters (in alphabetical order) with A-c and A-c ranges
[^ABC] matches any character except all characters in []
desk| Chair matches any one of the desk and Chair
[ABC] [DEF] Association. Match any character in a, B, and C, and then follow any of the characters in D, E, and F.
* Match the characters that appear 0 or more times in either a, B, or C
+ matches any of 1 or more occurrences of a, B, or C
? Match an empty string or a, B, or C in any one character
(blue| Black) berry combined with regular expressions, matching blueberry or blackberry
2.awk arithmetic operators
operator purpose
------------------
X^y X's Y power
X**y ditto
X%y calculates the remainder of x/y (modulo)
X+y x plus y
X-y minus y
X*y x multiply y
x/y x except Y
-y negative y (switch symbol for y); also known as a mesh reduction
++y y plus 1 use y (front Plus)
y++ use Y value and add 1 (suffix Plus)
--y y minus 1 use Y (front minus)
y--after use y minus 1 (suffix minus)
X=y assigns the value of Y to X
X+=y assigns the value of X+y to X
X-=y assigns an X-y value to X.
X*=y assigns the value of X*y to X
X/=y assigns the value of x/y to x X%=y assigns the x%y value to X
X^=y assigns the value of X^y to X
X**=y assigns the value of X**y to X
3.awk allowed Tests:
operator meaning
X==y x equals y
X!=y x is not equal to Y
X>y x is greater than Y
X>=y x is greater than or equal to Y
X<y x is less than Y
X<=y x is less than or equal to Y
X~re x matching Regular expression re
X!~re x mismatch Regular expression re
4.awk operators (in ascending order of priority)
=, + =, =, *=,/=,%=
||
&&
> >= < <= = =!= ~!~
XY (string link, ' x ' y ' becomes "xy")
+ -
* / %
++ --
5.awk built-in variable (predefined variable)
Description: The V item in the table represents the first tool to support the variable (same below): A=awk,n=nawk,p=posix Awk,g=gawk
V variable meaning default value
--------------------------------------------------------
N ARGC The number of command line arguments
G Argind The argv identifier of the file currently being processed
N ARGV array of command line arguments
G CONVFMT Digital Conversion format%.6g
P ENVIRON UNIX Environment variables
N ERRNO UNIX System error messages
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G fieldwidths A white space-delimited string of input field widths
A FILENAME The name of the current input file
P FNR current record number
A FS input Field separator space
G IGNORECASE Control Case Sensitive 0 (case sensitive)
A NF number of fields in the current record
A NR has been read out of the number of records
The output format of a ofmt number%.6g
A OFS output Field separator space
A ORS output Records separated Shing
A RS input Record He's separated Shing
N Rstart The string first matched by the matching function
N rlength The string length matched by the matching function
N subsep Subscript Separator "\034"
6.awk of built-in functions
V function purpose or return value
------------------------------------------------
N gsub (Reg,string,target) replaces string in target each time a regular expression reg matches
N Index (search,string) returns the position of the search string in string
A Length (string) Number of characters in string string
N Match (String,reg) returns the position of a regular expression reg-matched string
N printf (format,variable) format output, output variable variable in format provided by format.
N-Split (String,store,delim) decomposes a string into an array element of the store based on the delim of the delimiter
N sprintf (format,variable) returns a formatted data containing format, variables is the data to be placed in a string
G strftime (Format,timestamp) returns a date or time series based on format, TIMESTMP is the time returned by the Systime () function
N Sub (reg,string,target) The first time a regular expression reg matches, replace the string in the target string
A substr (String,position,len) returns a substring of Len characters starting at position
P totower (String) returns the corresponding lowercase characters in a string
P ToUpper (String) returns the corresponding uppercase characters in a string
Cotangent (radians) of a atan (x,y) x
Cosine of N cos (x) x (radians)
x power of a exp (x) E
Integer part of a int (x) x
The natural pair value of a log (x) x
N the random number between rand () 0-1
Sine (radians) of N sin (x) x
The square root of a sqrt (x) x
A Srand (x) initializes the random number generator. If x is omitted, the system () is used
G System () returns the time elapsed since January 1, 1970 (in seconds)