Several common usages of awk under Unix

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

More Wonderful content: http://www.bianceng.cn/database/Oracle/

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)