How to split a string in bash delimited by tab - bash

Question

I'm trying to split a tab delimitted field in bash.
I am aware of this answer: how to split a string in shell and get the last field
But that does not answer for a tab character.
I want to do get the part of a string before the tab character, so I'm doing this:
x=`head -1 my-file.txt`
echo ${x%\t*}
But the \t is matching on the letter 't' and not on a tab. What is the best way to do this?
Thanks

Answer 1

If your file look something like this (with tab as separator):
1st-field 2nd-field
you can use cut to extract the first field (operates on tab by default):
$ cut -f1 input
1st-field
If you're using awk, there is no need to use tail to get the last line, changing the input to:
1:1st-field 2nd-field
2:1st-field 2nd-field
3:1st-field 2nd-field
4:1st-field 2nd-field
5:1st-field 2nd-field
6:1st-field 2nd-field
7:1st-field 2nd-field
8:1st-field 2nd-field
9:1st-field 2nd-field
10:1st-field 2nd-field
Solution using awk:
$ awk 'END {print $1}' input
10:1st-field
Pure bash-solution:
#!/bin/bash
while read a b;do last=$a; done < input
echo $last
outputs:
$ ./tab.sh
10:1st-field
Lastly, a solution using sed
$ sed '$s/\(^[^\t]*\).*$/\1/' input
10:1st-field
here, $ is the range operator; i.e. operate on the last line only.
For your original question, use a literal tab, i.e.
x="1st-field 2nd-field"
echo ${x% *}
outputs:
1st-field

Answer 2

Use $'ANSI-C' strings in the parameter expansion:
$ x=$'abc\tdef\tghi'
$ echo "$s"
abc def ghi
$ echo ">>${x%%$'\t'*}<<"
>>abc<<

Answer 3

read field1 field2 <<< ${tabDelimitedField}
or
read field1 field2 <<< $(command_producing_tab_delimited_output)

Answer 4

Use awk.
echo $yourfield | awk '{print $1}'
or, in your case, for the first field from the the last line of a file
tail yourfile | awk '{x=$1}END{print x}'

Answer 5

There is an easy way for a tab separated string : convert it to an array.
Create a string with tabs ($ added before for '\t' interpretation) :
AAA=$'ABC\tDEF\tGHI'
Split the string as an array using parenthesis :
BBB=($AAA)
Get access to any element :
echo ${BBB[0]}
ABC
echo ${BBB[1]}
DEF
echo ${BBB[2]}
GHI

Answer 6

x=first$'\t'second
echo "${x%$'\t'*}"
See QUOTING in man bash

Answer 7

The answer from https://stackoverflow.com/users/1815797/gniourf-gniourf hints at the use of built in field parsing in bash, but does not really complete the answer. The use of the IFS shell parameter to set the input field separate will complete the picture and give the ability to parse files which are tab-delimited, of a fixed number of fields, in pure bash.
echo -e "a\tb\tc\nd\te\tf" > myfile
while IFS='<literaltab>' read f1 f2 f3;do echo "$f1 = $f2 + $f3"; done < myfile
a = b + c
d = e + f
Where, of course, is replaced by a real tab, not \t. Often, Control-V Tab does this in a terminal.