CODEWITHSUNDEEP
tabsawkfieldseparator
user2662766
user2662766

Reputation: 51

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

The default for white-space field separators, such as tab when using FS = "\t", in AWK is either one or many. Therefore, if you want to read in a tab separated file with null values in some columns (other than the last), it skips over them. For example:

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

$3 would refer to 4, not the null "" even though there are clearly two tabs.

What should I do so that I can specify the field separator to be one tab only, so that $4 would refer to 4 and not 5?

Upvotes: 5

Views: 19125

Answers (1)

shellter
shellter

Reputation: 37258

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

output

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

So you can remove the dbl-quotes in your original string, and get

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

output2

$3= $4=4

You're right, the default FS is white space, with the caveat that space and tab char next to each other, would qualify as 1 FS instance. So to use just "\t" as your FS, you can do as above as a cmd-line argument, or you can include an explict reset on FS, usually done in a BEGIN block, like

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

IHTH

Upvotes: 5

Related Questions