Linux文本处理三剑客：awk（内置函数详解笔记）

# 反正切函数
awk 'BEGIN {
  PI = 3.14159265
  x = -10
  y = 10
  result = atan2 (y,x) * 180 / PI;
  printf "对于 (x=%f, y=%f)，反正切值为 %f 度\n", x, y, result
}'
 
 
# 余弦函数
awk 'BEGIN {
  PI = 3.14159265
  param = 60
  result = cos(param * PI / 180.0);
  printf "%f 度的余弦值为 %f\n", param, result
}'
 
 
# 自然指数函数
awk 'BEGIN {
  param = 5
  result = exp(param);
  printf "%f 的自然指数值为 %f\n", param, result
}'
 
 
# 取整函数
awk 'BEGIN {
  param = 5.12345
  result = int(param)
  print "Truncated value =", result
}'
 
 
 
# 自然对数函数
awk 'BEGIN {
  param = 5.5
  result = log (param)
  printf "log(%f) = %f\n", param, result
}'
 
 
# 随机数函数
awk 'BEGIN {
  print "Random num1 =" , rand()
  print "Random num2 =" , rand()
  print "Random num3 =" , rand()
}'
 
 
#正弦函数
awk 'BEGIN {
  PI = 3.14159265
  param = 30.0
  result = sin(param * PI /180)
  printf "The sine of %f degrees is %f.\n", param, result
}'
 
 
 
# 平方根函数
awk 'BEGIN {
  param = 1024.0
  result = sqrt(param)
  printf "sqrt(%f) = %f\n", param, result
}'
 
 
# 设置随机数种子
awk 'BEGIN {
  param = 10
  printf "srand() = %d\n", srand()
  printf "srand(%d) = %d\n", param, srand(param)
}'
 

# 按字母顺序排列数组元素
$ awk 'BEGIN {
  arr[0] = "Three"
  arr[1] = "One"
  arr[2] = "Two"
  print "排序前数组元素："
  for (i in arr) {
    print arr[i]
  }
  asort(arr)
  print "排序后数组元素："
  for (i in arr) {
    print arr[i]
  }
}'
 
 
 
# 按索引顺序排列数组元素
awk 'BEGIN {
  arr["Two"] = 1
  arr["One"] = 2
  arr["Three"] = 3
  asorti(arr)
  print "排序后数组索引："
  for (i in arr) {
    print arr[i]
  }
}'
 
 
# 替换字符串
awk 'BEGIN {
  str = "Hello, World"
  print "替换前字符串 = " str
  gsub("World", "Jerry", str)
  print "替换后字符串 = " str
}'
 
 
# 查找子串的位置
awk 'BEGIN {
  str = "One Two Three"
  subs = "Two"
  ret = index(str, subs)
  printf "子串 \"%s\" 在第 %d 个位置找到.\n", subs, ret
}'
 
 
 
 
# 获取字符串长度
awk 'BEGIN {
  str = "Hello, World !!!"
  print "长度 = ", length(str)
}'
 
 
 
# 使用正则表达式匹配子串
awk 'BEGIN {
  str = "One Two Three"
  subs = "Two"
  ret = match(str, subs)
  printf "子串 \"%s\" 在第 %d 个位置找到.\n", subs, ret
}'
 
 
 
# 将字符串分割为数组
awk 'BEGIN {
  str = "One,Two,Three,Four"
  split(str, arr, ",")
  print "数组包含以下元素："
  for (i in arr) {
    print arr[i]
  }
}'
 
 
# 使用 sprintf() 格式化字符串
awk 'BEGIN {
  str = sprintf("%s", "Hello, World !!!")
  print str
}'
 
 
# 将字符串转换为数字
awk 'BEGIN {
  print "Decimal num = " strtonum("123")
  print "Octal num = " strtonum("0123")
  print "Hexadecimal num = " strtonum("0x123")
}'
 
 
 
 
# 使用 sub() 替换字符串
awk 'BEGIN {
  str = "Hello, World"
  print "替换前字符串 = " str
  sub("World", "Jerry", str)
  print "替换后字符串 = " str
}'
 
 
# 获取子字符串
awk 'BEGIN {
  str = "Hello, World !!!"
  subs = substr(str, 1, 5)
  print "Substring = " subs
}'
 
 
# 小写转换
awk 'BEGIN {
  str = "HELLO, WORLD !!!"
  print "Lowercase string = " tolower(str)
}'
 
 
 
# 大写转换
awk 'BEGIN {
  str = "hello, world !!!"
  print "Uppercase string = " toupper(str)
}'
 

# 获取当前时间戳
awk 'BEGIN {
    print "Number of seconds since the Epoch = " systime()
}'
# 将字符串转换为时间戳
awk 'BEGIN {
    print "Number of seconds since the Epoch = " mktime("2014 12 14 30 20 10")
}'
 
# 格式化时间戳
awk 'BEGIN {
    print strftime("Time = %m/%d/%Y %H:%M:%S", systime())
}'
 
# 打印当前星期几
awk 'BEGIN {
  print strftime("%A")
}'

# 位与操作
awk 'BEGIN {
    num1 = 10
    num2 = 6
    printf "(%d AND %d) = %d\n", num1, num2, and(num1, num2)
}'
 
# 按位求补
awk 'BEGIN {
    num1 = 10
    printf "compl(%d) = %d\n", num1, compl(num1)
}'
 
 
# 左移位操作
awk 'BEGIN {
    num1 = 10
    printf "lshift(%d) by 1 = %d\n", num1, lshift(num1, 1)
}'
 
 
# 向右移位操作。
awk 'BEGIN {
    num1 = 10
    printf "rshift(%d) by 1 = %d\n", num1, rshift(num1, 1)
}'
 
 
 
# 按位或操作。
awk 'BEGIN {
    num1 = 10
    num2 = 6
    printf "(%d OR %d) = %d\n", num1, num2, or(num1, num2)
}'
 
 
# 按位异或操作
[jerry]$ awk 'BEGIN {
    num1 = 10
    num2 = 6
    printf "(%d XOR %d) = %d\n", num1, num2, xor(num1, num2)
}'

# 关闭管道
awk 'BEGIN {
    cmd = "tr [a-z] [A-Z]"
    print "hello, world !!!" |& cmd
    close(cmd, "to")
    cmd |& getline out
    print out;
    close(cmd);
}'
 
 
# 从数组中删除元素
awk 'BEGIN {
    arr[0] = "One"
    arr[1] = "Two"
    arr[2] = "Three"
    arr[3] = "Four"
    print "删除前:"
    for (i in arr) {
        print arr[i]
    }
    delete arr[0]
    delete arr[1]
    print "删除后:"
    for (i in arr) {
        print arr[i]
    }
}'
 
 
# 终止脚本执行
awk 'BEGIN {
    print "Hello, World !!!"
    exit 10
    print "AWK never executes this statement."
}'
 
 
 
# 刷新打开文件或管道的缓冲区
fflush([output-expr])
 
 
 
# 读入下一行
awk '{getline; print $0}' file.txt 
 
 
# 执行特定的命令然后返回其退出状态。返回值为 0 表示命令执行成功；非 0 表示命令执行失败。
awk 'BEGIN { ret = system("date"); print "Return value = " ret }'