UNIX for Advanced & Expert Users

But I love my back-ticks - I know exactly how to escape them (after too many years) - I always seem to end unbalanced with ().

However, I shall take the hint. (One more trick for this dog... aka - not too old yet!)

You might want to try some formatting help in this case, when the subshell commands get more complex. This certainly helps me to keep track:

Code:

var=$( \
        command1 |\
        command2 |\
        command3 \
     )

I hope this helps.

bakunin

You don't need to use a \newline.
Neither for $( ) that contains normal shell code that does not need to know it's within $( ),
nor for | that is one of the operators that work at the end of the line, expecting the operand on the next line.
You can even nest $( ), unlike the old ` ` where each more level needs some extra \escapes.

Code:

var=$(
  command1 |
  command2 |
  command3
  localvar=$(
    echo "hello world"
  )
)

Hmm, 20 years of using ksh and i didn't know that. That is embarrassing.

bakunin

Then let me continue with lession#2.
Within $( ) there is a parser problem with the old style case statements.

Code:

#!/bin/bash
res=$(
  case $1 in
  1) echo 1;;
  esac
)
# syntax error in bash3 and ksh88
# workaround:
# (1) echo 1;;
echo "$res"

But bash4 and ksh93 have got a fix.

Don't be. I have 38+ years on UNIX and I still use \ - because often - first I am assigning the "command" to a variable (as the string) and later am executing it (the variable). Same as I (must) do in files like configure.{ac|in}, Makefile, etc..

In short - better one \ too many that one short.

I'm not sure on using backquotes is wrong per se.
$(command) are both `command` are both currently valid syntax and in standards.
Exception being, that actually backquotes should work on even the oldest shells (and new ones), while other form might not.

If i'm not mistaken backquotes are still the lowest common denominator for command substitution if you wish your scripts to work anywhere without touching

But today it's hard to find such shells as defaults or even existing on operating systems.
So i tend to write scripts using $(command) method, as well as promote such way.

Regards
Peasant.