技术分享 AWK 内置函数

$ awk 'BEGIN {
  PI = 3.14159265
  x = -10
  y = 10
  result = atan2 (y,x) * 180 / PI;

  printf "The arc tangent for (x=%f, y=%f) is %f degrees\n", x, y, result
}'

输出结果为：

The arc tangent for (x=-10.000000, y=10.000000) is 135.000000 degrees

$ awk 'BEGIN {
  PI = 3.14159265
  param = 60
  result = cos(param * PI / 180.0);

  printf "The cosine of %f degrees is %f.\n", param, result
}'

输出结果为：

The cosine of 60.000000 degrees is 0.500000.

$ awk 'BEGIN {
  PI = 3.14159265
  param = 30.0
  result = sin(param * PI /180)

  printf "The sine of %f degrees is %f.\n", param, result
}'

输出结果为：

The sine of 30.000000 degrees is 0.500000.

$ awk 'BEGIN {
  param = 5
  result = exp(param);

  printf "The exponential value of %f is %f.\n", param, result
}'

输出结果为：

The exponential value of 5.000000 is 148.413159.

$ awk 'BEGIN {
  param = 5.5
  result = log (param)

  printf "log(%f) = %f\n", param, result
}'

输出结果为：

log(5.500000) = 1.704748

$ awk 'BEGIN {
  param = 1024.0
  result = sqrt(param)

  printf "sqrt(%f) = %f\n", param, result
}'

输出结果为：

sqrt(1024.000000) = 32.000000

$ awk 'BEGIN {
  param = 5.12345
  result = int(param)

  print "Truncated value =", result
}'

输出结果为：

Truncated value = 5

$ awk 'BEGIN {
  print "Random num1 =" , rand()
  print "Random num2 =" , rand()
  print "Random num3 =" , rand()
}'

输出结果为：

Random num1 = 0.237788
Random num2 = 0.291066
Random num3 = 0.845814

$ awk 'BEGIN {
  param = 10

  printf "srand() = %d\n", srand()
  printf "srand(%d) = %d\n", param, srand(param)
}'

输出结果为：

srand() = 1
srand(10) = 1417959587

$ awk 'BEGIN {
    str = "Hello, World"

    print "String before replacement = " str

    gsub("World", "Jerry", str)

    print "String after replacement = " str
}'

输出结果为：

String before replacement = Hello, World
String after replacement = Hello, Jerry

$ awk 'BEGIN {
    str = "Hello, World"

    print "String before replacement = " str

    sub("World", "Jerry", str)

    print "String after replacement = " str
}'

输出结果为：

String before replacement = Hello, World
String after replacement = Hello, Jerry

$ awk 'BEGIN {
    str = "Hello, World !!!"
    subs = substr(str, 1, 5)

    print "Substring = " subs
}'

输出结果为：

Substring = Hello

$ awk 'BEGIN {
    str = "One Two Three"
    subs = "Two"

    ret = index(str, subs)

    printf "Substring \"%s\" found at %d location.\n", subs, ret
}'

输出结果为：

Substring "Two" found at 5 location.

$ awk 'BEGIN {
    str = "Hello, World !!!"

    print "Length = ", length(str)
}'

输出结果为：

Substring "Two" found at 5 location.

$ awk 'BEGIN {
    str = "Hello, World !!!"
    subs = substr(str, 1, 5)

    print "Substring = " subs
}'

输出结果为：

Substring = Hello

$ awk 'BEGIN {
    str = "One Two Three"
    subs = "Two"

    ret = match(str, subs)

    printf "Substring \"%s\" found at %d location.\n", subs, ret
}'

输出结果为：

Substring "Two" found at 5 location.

$ awk 'BEGIN {
    str = "One,Two,Three,Four"

    split(str, arr, ",")

    print "Array contains following values"

    for (i in arr) {
        print arr[i]
    }
}'

输出结果为：

Array contains following values
One
Two
Three
Four

$ awk 'BEGIN {
    str = "HELLO, WORLD !!!"

    print "Lowercase string = " tolower(str)
}'

输出结果为：

Lowercase string = hello, world !!!

$ awk 'BEGIN {
    str = "hello, world !!!"

    print "Uppercase string = " toupper(str)
}'

输出结果为：

Uppercase string = HELLO, WORLD !!!

$ awk 'BEGIN {
    str = sprintf("%s", "Hello, World !!!")

    print str
}'

输出结果为：

Hello, World !!!

$ awk 'BEGIN {
    print "Decimal num = " strtonum("123")
    print "Octal num = " strtonum("0123")
    print "Hexadecimal num = " strtonum("0x123")
}'

输出结果为：

Decimal num = 123
Octal num = 83
Hexadecimal num = 291

$ awk 'BEGIN {
    print "Number of seconds since the Epoch = " mktime("2014 12 14 30 20 10")
}'

输出结果为：

Number of seconds since the Epoch = 1418604610

$ awk 'BEGIN {
    print strftime("Time = %m/%d/%Y %H:%M:%S", systime())
}'

输出结果为：

Time = 12/14/2014 22:08:42

awk 'BEGIN{now=systime();print now}'

输出结果为：

1343210982

$ awk 'BEGIN {
    num1 = 10
    num2 = 6

    printf "(%d AND %d) = %d\n", num1, num2, and(num1, num2)
}'

输出结果为：

(10 AND 6) = 2

$ awk 'BEGIN {
    num1 = 10

    printf "compl(%d) = %d\n", num1, compl(num1)
}'

输出结果为：

compl(10) = 9007199254740981

$ awk 'BEGIN {
    num1 = 10

    printf "lshift(%d) by 1 = %d\n", num1, lshift(num1, 1)
}'

输出结果为：

lshift(10) by 1 = 20

$ awk 'BEGIN {
    num1 = 10

    printf "rshift(%d) by 1 = %d\n", num1, rshift(num1, 1)
}'

输出结果为：

rshift(10) by 1 = 5

$ awk 'BEGIN {
    num1 = 10
    num2 = 6

    printf "(%d OR %d) = %d\n", num1, num2, or(num1, num2)
}'

输出结果为：

(10 OR 6) = 14

$ awk 'BEGIN {
    num1 = 10
    num2 = 6

    printf "(%d XOR %d) = %d\n", num1, num2, xor(num1, num2)
}'

输出结果为：

(10 bitwise xor 6) = 12

$ awk 'BEGIN {
    cmd = "tr [a-z] [A-Z]"
    print "hello, world !!!" |& cmd
    close(cmd, "to")
    cmd |& getline out
    print out;
    close(cmd);
}'

输出结果为：

HELLO, WORLD !!!

• 第一条语句 cmd = "tr [a-z] [A-Z]" 在　AWK 中建立了一个双向的通信通道。
• 第二条语句 print 为 tr 命令提供输入。&| 表示双向通信。
• 第三条语句 close(cmd, "to") 完成执行后关闭 to 进程。
• 第四条语句 cmd |& getline out 使用 getline 函数将输出存储到 out 变量中。
• 接下来的输出语句打印输出的内容，最后 close 函数关闭 cmd。

$ awk 'BEGIN {
    arr[0] = "One"
    arr[1] = "Two"
    arr[2] = "Three"
    arr[3] = "Four"

    print "Array elements before delete operation:"
    for (i in arr) {
        print arr[i]
    }

    delete arr[0]
    delete arr[1]

    print "Array elements after delete operation:"
    for (i in arr) {
        print arr[i]
    }
}'

输出结果为：

Array elements before delete operation:
One
Two
Three
Four

Array elements after delete operation:
Three
Four

$ awk 'BEGIN {
    print "Hello, World !!!"

    exit 10

    print "AWK never executes this statement."
}'

输出结果为：

Hello, World !!!

使用 getline 从文件 marks.txt 中读入一行并输出：

$ awk '{getline; print $0}' marks.txt

，AWK 从文件 marks.txt 中读入一行存储到变量 0 中。在下一条语句中，我们使用 getline 读入下一行。因此AWK读入第二行并存储到 0 中。最后，AWK 使用 print 输出第二行的内容。这个过程一直到文件结束。

当模式串匹配成功后程序并不执行任何操作：

$ awk '{if ($0 ~/Shyam/) next; print $0}' marks.txt

首先创建两个文件。 file1.txt 内容如下:

file1:str1
file1:str2
file1:str3
file1:str4

文件 file2.txt 内容如下：

file2:str1
file2:str2
file2:str3
file2:str4

现在我们来测试 nextfile 函数。

$ awk '{ if ($0 ~ /file1:str2/) nextfile; print $0 }' file1.txt file2.txt

输出结果为：

file1:str1
file2:str1
file2:str2
file2:str3
file2:str4

创建文件 functions.awk，内容如下：

function addition(num1, num2)
{
    result = num1 + num2

    return result
}

BEGIN {
    res = addition(10, 20)
    print "10 + 20 = " res
}

执行该文件：

$ awk -f functions.awk 
10 + 20 = 30

$ awk 'BEGIN { ret = system("date"); print "Return value = " ret }'

输出结果为：

Sun Dec 21 23:16:07 IST 2014
Return value = 0