问使用awk命令向后显示行

EN

$ cat text 
Hello World
How are you
I love computer science,
I am using awk,
And it is hard.

$ awk 'NR<3{print}NR>=3{for(i=0; i<NF; i++){printf "%s ",$(NF-i);} printf "\n";}' text                                                            
Hello World
How are you
science, computer love I 
awk, using am I 
hard. is it And

$ awk 'NR>=3{for(i=0; i<NF; i++){printf "%s ",$(NF-i);} printf "\n";}' text                                                            
science, computer love I 
awk, using am I 
hard. is it And

$ awk 'NR>=3 && NR<=5{for(i=0; i<NF; i++){printf "%s ",$(NF-i);} printf "\n";}' text

awk -v start=3 -v end=5 'FNR>=start && FNR<=end{for(;NF>0;NF--){printf("%s%s",$NF,NF==1?RS:FS)}}'   Input_file

science, computer love I
awk, using am I
hard. is it And

awk -v start=3 -v end=5 '            ##Mentioning variables named start and end where start is denoting the starting line and end is denoting end line which we want to print.
FNR>=start && FNR<=end{              ##Checking condition here if variable FNR(awk out of the box variable) value is greater than or equal to variable start AND FNR value is less than or equal to end variable. If condition is TRUE then do following:
  for(;NF>0;NF--){                   ##Initiating a for loop which starts from value of NF(Number of fields, which is out of the box variable of awk) and it runs till NF is 0.
    printf("%s%s",$NF,NF==1?RS:FS)}  ##Printing value of NF(value of field) and other string will be either space of new line(by checking when field is first then print new line as print space).
}
' Input_file                         ##Mentioning Input_file name here.

$ cat tst.awk
NR>2 && NR<6 {
    for (i=NF; i>0; i--) {
        printf "%s%s", $i, (i>1?OFS:ORS)
    }
}

$ awk -f tst.awk file
science, computer love I
awk, using am I
hard. is it And