linux - awk 命令来查找和替换值

Question

我需要帮助 w.r.t.下面的代码我很难理解。如果有人能抽出一点时间来解释这一点，真的很感激。

它的主要作用是根据 file1 的 col1 中的值在 file2 中基于 col1 定位一行并替换 file2 中的 7 个列值，这些列的位置通过 -v 标志作为输入提供。

awk --lint '-F|' -v col1pos=5 -v col2pos=29 -v col3pos=114 -v col4pos=115 -v col5pos= -v col6pos=26 -v col7pos= -v col8pos= 'BEGIN{OFS = FS; a[var 2] = col1pos; a[var 3] = col2pos; a[var 4] = col3pos; a[var 5] = col4pos; a[var 6] = col5pos; a[var 7] = col6pos; a[var 8] = col7pos; a[var 9] = col8pos} NR == FNR {a[$1] = $2; for (i
= 3; i <= 9; ++i) a[$1 FS i] = $i; next} $col1pos in a {for (i = 9; i >= 3; --i) if (length(a[var i]) > 0) $(a[var i]) = a[$col1pos FS i]; $col1pos = a[$col1pos]}1' file1 file2

Answer 1

由于没有提供示例，因此很难理解您的完整问题；如果我们谈论代码，那么我已尽力解释如下。请仔细阅读，如有任何疑问，请告诉我。

代码说明:

awk --lint '-F|' -v col1pos=5 -v col2pos=29 -v col3pos=114 -v col4pos=115 -v col5pos= -v col6pos=26 -v col7pos= -v col8pos= '                   ##Starting awk program from here and mentioning all variables with values as per OP need.
BEGIN{                                   ##Starting BEGIN section of awk program which will be executed before Input_file reading.
  OFS = FS                               ##Setting OFS to FS (1st point)
  a[var 2] = col1pos                     ##Creating an array named a whose index is var 2(2nd point) and setting its value to variable col1pos. Similarly creating other elements of array in next statements.
  a[var 3] = col2pos
  a[var 4] = col3pos
  a[var 5] = col4pos
  a[var 6] = col5pos
  a[var 7] = col6pos
  a[var 8] = col7pos
  a[var 9] = col8pos
}                                        ##Closing BLOCK for BEGIN section here.
NR == FNR{                               ##Checking condition FNR==NR which will be TRUE when first Input_file named file1 is being read.
  a[$1]=$2                               ##Creating an array named a whose index is $1 and value is $2 of current line.
  for(i=3;i<=9;i++){                     ##Starting a for loop which starts from i=3 to till value of 9 here.
    a[$1 FS i]=$i                        ##Creating an array named a whose index is $1 FS and i and value is $i(i variable value column)
  }
    next                                 ##next will make sure no further statements are getting executed from here.
}                                        ##Closing BLOCK for FNR==NR condition here.
($col1pos in a){                         ##Checking condition if field number whose value is variable col1pos is present in array a, if yes then go further.
  for(i = 9; i >= 3; --i){               ##Starting a for loop from i=9 to till value of 3.
    if(length(a[var i]) > 0){            ##Checking condition if length of array a with index var i value is greater than 0 then do following.
      $(a[var i]) = a[$col1pos FS i]     ##Assigning field value(which will be decided on value of variable a[var i]) and setting it to value of array a with index $col1pos FS i.
    }                                    ##Closing if condition BLOCK here.
    $col1pos = a[$col1pos]               ##Setting value of field(which will be decided as per variable value col1pos) and setting it to array a value whose value is, value of field(col1pos).
  }                                      ##Closing BLOCK for; for loop here.
}                                        ##Closing BLOCK for condition here.
1                                        ##Mentioning 1 will print edited/non-edited lines.
' file1 file2                            ##Mentioning Input_file names here.

注意:对于代码的改进，我提到了2点，在这里提到它们的含义。

第一点:无需设置 OFS=FS因为默认情况下两者都与空格具有相同的值。

第二点:设置数组索引时要小心，如果它是一个字符串，则使用 a["string"]或者在使用变量 try a[variable] 的情况下