如何使用awk将带有标题的新列添加到csv答案

【问题标题】：How to add new column with header to csv with awk如何使用awk将带有标题的新列添加到csv
【发布时间】：2018-03-18 13:24:17
【问题描述】：

我在处理 CSV 的 bash 脚本中使用了一些 awk。 awk 这样做：

ORIG_FILE="score_model.csv"   
NEW_FILE="updates/score_model.csv"    
awk -v d="2017_01" -F"," 'BEGIN {OFS = ","} {$(NF+1)=d; print}' $ORIG_FILE > $NEW_FILE

这个转换是什么：

# before
model_description,      type,    effective_date, end_date
Inc <= 40K,             Retired, 08/05/2016,     07/31/2017
Inc > 40K Age <= 55 V5, Retired, 04/30/2016,     07/31/2017
Inc > 40K Age > 55 V5 , Retired, 04/30/2016,     07/31/2017

# after, bad
model_description,      type,    effective_date, end_date,   2017_01  
Inc <= 40K,             Retired, 08/05/2016,     07/31/2017, 2017_01
Inc > 40K Age <= 55 V5, Retired, 04/30/2016,     07/31/2017, 2017_01
Inc > 40K Age > 55 V5 , Retired, 04/30/2016,     07/31/2017, 2017_01

我希望新列有一个标题，以便新的 CSV 看起来像

# after, desired
model_description,      type,    effective_date, end_date,   cmpgn_group  
Inc <= 40K,             Retired, 08/05/2016,     07/31/2017, 2017_01
Inc > 40K Age <= 55 V5, Retired, 04/30/2016,     07/31/2017, 2017_01
Inc > 40K Age > 55 V5 , Retired, 04/30/2016,     07/31/2017, 2017_01

我知道有一种方法可以在第一行单独指定要执行的操作，但我无法弄清楚。

【问题讨论】：

标签： bash csv awk

【解决方案1】：

使用 sed

$ sed '1s/$/,\tcmpgn_group/; 2,$s/$/,\t2017_01/' file

即1st line：附加,\tcmpgn_group
对于2 to $：追加,\t2017_01

使用 awk

$ awk -v d="2017_01" -F"," 'FNR==1{a="cmpgn_group"} FNR>1{a=d} {print $0",\t"a}' f1

输出：

model_description,      type,    effective_date, end_date,      cmpgn_group
Inc <= 40K,             Retired, 08/05/2016,     07/31/2017,    2017_01
Inc > 40K Age <= 55 V5, Retired, 04/30/2016,     07/31/2017,    2017_01
Inc > 40K Age > 55 V5 , Retired, 04/30/2016,     07/31/2017,    2017_01

【讨论】：

【解决方案2】：

遵循 awk（您的解决方案有所改变）应该适合您。

ORIG_FILE="score_model.csv"   
NEW_FILE="updates/score_model.csv"    
awk -v d="2017_01" -F"," 'BEGIN {OFS = ","} FNR==1{$(NF+1)="cmpgn_group"} FNR>1{$(NF+1)=d;} 1' $ORIG_FILE > $NEW_FILE

解决方案二：或者让我们删除这个$(NF+1)(creating a new field方法）并尝试直接打印。

awk -v d="2017_01" -F"," 'BEGIN {OFS = ","} {printf("%s%s",$0,FNR>1?d RS:"cmpgn_group" RS)}' $ORIG_FILE > $NEW_FILE

上述命令说明：

awk -v d="2017_01" -F"," ' ##Setting valur of variable named d as 2017_01 and setting field separator as comma.
BEGIN{                     ##Starting BEGIN section of awk here.
  OFS = ","                ##Setting Output field separator as comma here.
}                          ##Closing BEGIN block here.
{
  printf("%s%s",$0,FNR>1?d RS:"cmpgn_group" RS) ##Using printf here to print the lines. So %s%s means to print 2 strings here. First I am simply printing $0(current line). Then while printing second string using condition FNR>1(when line number is greater than 1) then print variable d(which we want to add at last) with RS(to print a new line here). Else(if condition FNR>1 is not true) then it means it is very first line of Input_file and print string "cmpn_groups" with RS(record separator) whose default value is a new line.
}
' $ORIG_FILE > $NEW_FILE   ##Mentioning Input_file named #ORIG_FILE and redirecting it's output to $NEW_FILE here.

【讨论】：

【解决方案3】：

awk -v d="2017_01" 'BEGIN{FS=OFS=","} {print $0, (NR>1?d:"cmpgn_group")}' file

【讨论】：