在R中管道awk

Question

I am trying to read in this fixed-width file in R. I want to read in only the first 3 columns with lengths 2, 2 and 6, such that the second variable has the value "A". Note that the second variable has two spaces but is actually only one character. I am using this command:

b = trim(read.csv(pipe("awk -v FIELDWIDTHS='2 2 6' -v OFS=',' '($2=='A '){ $1=$1 ''; print }'</path/rawk.txt"),header=F))

I am getting this error:

awk: cmd. line:1: ($2==A
awk: cmd. line:1:       ^ unexpected newline or end of string
Error in read.table(file = file, header = header, sep = sep, quote = quote,  : 
  no lines available in input

If I remove the empty space in 'A ':

b = trim(read.csv(pipe("awk -v FIELDWIDTHS='2 2 6' -v OFS=',' '($2=='A'){ $1=$1 ''; print }'</path/rawk.txt"),header=F))

I still get this error:

Error in read.table(file = file, header = header, sep = sep, quote = quote,  : 
  no lines available in input

What am I doing wrong?

Answer 1

This seems to work:

read.csv(pipe("awk -v FIELDWIDTHS='2 2 6' -v OFS=',' '($2==\"A \"){ $1=$1 \'\'; print }'<rawk.txt"),header=FALSE)


  V1 V2    V3
1 10 A  10001
2 10 A  10002
3 10 A  10003

But I'm not sure what the $1=$1 is all about...

Answer 2

对于这种简单的内容，您是否可以更轻松地查看行的子字符串，而不是考虑其中的“实际”固定宽度字段？

b = trim(read.csv(pipe("awk 'substr($0,3,2)==\"A \"' /path/rawk.txt"),header=F))