3

There is \t option for horizontal tab in echo

wolf@linux:~$ echo hello
hello
wolf@linux:~$ 

wolf@linux:~$ echo -e '\thello'
    hello
wolf@linux:~$

Is there any similar option in read?

wolf@linux:~$ read -p 'hello '
hello wolf
wolf@linux:~$ 
wolf@linux:~$ read -p '\thello '
\thello wolf
wolf@linux:~$

Desired Output

wolf@linux:~$ read -p '\thello ' <- need something to produce something like tab or `\t` in `echo`
    hello wolf
wolf@linux:~$
Wolf
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2 Answers2

5

You can always use the ksh93-style $'...' form of quotes that understand those escape sequences:

IFS= read -r -p $'\thello ' var

(the IFS= and -r are not relevant, I'm just adding them here as calling read without them rarely makes sense).

Note that -p is not a standard sh function. In ksh/zsh, -p is to read from the co-process and prompts are specified with read 'var?Prompt: '. It's unfortunate that bash chose to introduce an incompatible API here. You don't have to use -p though, you can just do portably:

printf >&2 '\thello '
IFS= read -r var

printf does recognise those escape sequences in its format argument, and arguments for %b specifiers. Whether echo recognises them (or accepts a -e option to recognise them) depends on the implementation and for many implementations (including bash's builtin) on build time and runtime settings, so is best avoided.

Stéphane Chazelas
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1

You could always simply add 8 spaces:

read -p '        hello '

But yes, you can also get an actual tab character:

read -p $'\t''hello '

Or

read -p "$(echo -e '\thello ')"

Or

read -p "$(printf '\thello ')"
terdon
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  • Why `4` spaces? TAB stops are generally 8 columns apart in terminals. – Stéphane Chazelas Oct 15 '20 at 16:04
  • @StéphaneChazelas because that's the OP had. – terdon Oct 15 '20 at 16:08
  • It looks more like it's how stackexchange renders tabs. It's actually really annoying as most terminals and web browsers do render them 8 columns apart, so when you're copy pasting a TAB from a terminal to the editing textarea when writing a SE post, it's fine, but when you post the article, the formatting is mangled. – Stéphane Chazelas Oct 15 '20 at 16:13
  • @StéphaneChazelas eh, either way, the point was just that you can add N spaces and might not need a tab, specifically. I'm happy to change it to 8, if you prefer. – terdon Oct 15 '20 at 16:21