awk - 如何使用 awk 命令使用关联数组来计算文件中特定字符的出现次数

Question

我有这样的文件:

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我想将每个域的出现次数计算为

Domain Name No of Email
-----------------------
com         1
in          3
uk          1

Answer 1

这是一个纯 POSIX awk解决方案(从sort程序内部调用awk):

awk -F. -v OFS='\t' '
    # Build an associative array that maps each unique top-level domain
    # (taken from the last `.`-separated field, `$NF`) to how often it
    # occurs in the input.
  { a[$NF]++ }

  END { 
      # Print the header.
    print "Domain Name", "No of Email"
    print "----------------------------"
     # Output the associative array and sort it (by top-level domain).
    for (k in a) print k, a[k] | "sort"
  }
' file

---

如果您有GNU awk 4.0或更高，无需外部即可凑合sort甚至可以轻松地从 gawk 内部控制排序字段程序:

gawk -F. -v OFS='\t' '
    # Build an associative array that maps each unique top-level domain
    # (taken from the last `.`-separated field, `$NF`) to how often it
    # occurs in the input.
  { a[$NF]++ }

  END { 
      # Print the header.
    print "Domain Name", "No of Email"
    print "----------------------------"
     # Output the associative array and sort it (by top-level domain).
     # First, control output sorting by setting the order in which 
     # the associative array will be looped over by, via the special
     # PROCINFO["sorted_in"] variable; e.g.:
     #  - Sort by top-level domain, ascending:  "@ind_str_asc"
     #  - Sort by occurrence count, descending: "@val_num_desc"
    PROCINFO["sorted_in"]="@ind_str_asc"
    for (k in a) print k, a[k]
  }
' file