I have a text file (xxx.txt) with this format:
kw1 kw2 kw3 kw4
kw1 kw2 kw3 kw4
...
but sometimes, the line is abnormal, like this:
kw1
My shell command is
cat xxx.txt|awk '{ print $2;print $3}'
How to ignore the abnormal line, and continue printing?
I suggest:
awk 'NF>=3{print $2;print $3}' xxx.txt
NF: The number of fields in the current input record.
See: 8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR
Based on your shown samples try following once. We could use only single print to print the two fields with a new line here
awk 'NF>=3{print $2 ORS $3}' Input_file
Answering your title question how to ignore error line when print $2 but $2 it not exist in error line let file.txt content be
kw1 kw2 kw3 kw4
kw1 kw2 kw3 kw4
kw1
kw1 kw2 kw3 kw4
then
awk '($2!=""){print $2;print $3}' file.txt
output
kw2
kw3
kw2
kw3
kw2
kw3
Explanation: if you try to access field which is not present in given line you get empty string. I process lines only where given field is not empty.