How to specify *one* tab as field separator in AWK? -

the default white-space field separators, such tab when using fs = "\t", in awk either 1 or many. therefore, if want read in tab separated file null values in columns (other last), skips on them. example:

1 "\t" 2 "\t" "" "\t" 4 "\t" 5 

$3 refer 4, not null "" though there 2 tabs.

what should can specify field separator 1 tab only, $4 refer 4 , not 5?

 echo '1 "\t" 2 "\t" "" "\t" 4 "\t" 5' | awk -f"\t" '{print "$3="$3 , "$4="$4}' 

output

$3=" "" " $4=" 4 "  

so can remove dbl-quotes in original string, , get

echo '1\t2\t\t4\t5' | awk -f"\t" '{print "$3="$3 , "$4="$4}' 

output2

$3= $4=4 

you're right, default fs white space, caveat space , tab char next each other, qualify 1 fs instance. use "\t" fs, can above cmd-line argument, or can include explict reset on fs, done in begin block, like

echo '1 "\t" 2 "\t" "" "\t" 4 "\t" 5' | awk 'begin{fs="\t"}{print "$3="$3 , "$4="$4}' 

ihth