2

I am frequently using a command line program that I provide with arguments that contain parentheses. For simplicity, let's say I'm writing

echo 'bar(1,3)'

I would like to omit the quotes. However, if I do that I get syntax errror near unexpected token '('. I guess this is related to subshells. I am willing to disable those, if that's the only way. (though a subshell cannot be started if it is not at the beginning of the command anyway, so they are no reason to forbid parentheses in the arguments, as far as I can tell)

  • 2
    Try echo bar\(1,3\) – msp9011 Aug 24 '18 at 12:10
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    Why do you want to omit the quotes? – Flimm Aug 24 '18 at 12:16
  • 1
    You can not "disable subshells". – Kusalananda Aug 24 '18 at 12:26
  • @Flimm I want to omit the quotes out of laziness and because I often forget them and then have to to even more typing – Bananach Aug 24 '18 at 12:50
4

( and ) are special token characters in the syntax of bash that are used in a number of operators including:

  • (...) subshell construct
  • func() compound-command function definitions
  • $(...) command substitution
  • <(...), >(...) process substitution
  • ((...)) arithmetic evaluation construct
  • $((...)) arithmetic expansion
  • a=(...), a+=(...) array assignment operators
  • @(...), +(...), *(...), ?(...) glob operators (with extglob)
  • [[ (a && b) || (c && d) ]] grouping conditional expression operators
  • [[ ... =~ ...(...)... ]] regexp operator.

echo a=(b) is a syntax error, but not export a=(b).

echo a) is a syntax error, unless there was an opening ( in the previous lines part of one of the constructs above.

While it may be possible to write a readline hook that adds quotes where needed around (, ) to avoid a syntax error, it would be considerable effort as it would mean doing a full parsing of the shell syntax.

A better approach may be to use a shortcut that quotes the current word when you realise too late that it contains characters special to the shell.

With zsh (assuming emacs mode):

bindkey -s '\e#' '\C@\eb\Cx\Cx\e"'

To have Alt+# quote the current word.

Or an approximation with bash (also assuming emacs mode):

bind "\"\e#\": \"'\e \eb'\C-X\C-X\""
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    I agree with your better approach. Thanks for the bash update. If anyone else needs this but has vi-mode enabled as I do, I modified this to bind "\"\e#\": \"'\eF a'". This puts quotes around the current argument as defined by the cursor until the closest space character before it. – Bananach Aug 24 '18 at 15:03
  • To the maintainers of this site, I suggest that you have a repository of such answers, so that they can be straightway accessed later on. – Rakesh Sharma Aug 25 '18 at 17:25

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