Linux bash: Multiple variable assignment

问题

Does exist in linux bash something similar to the following code in PHP:

list($var1, $var2, $var3) = function_that_returns_a_three_element_array() ;

i.e. you assign in one sentence a corresponding value to 3 different variables.

Let\'s say I have the bash function myBashFuntion that writes to stdout the string \"qwert asdfg zxcvb\". Is it possible to do something like:

(var1 var2 var3) = ( `myBashFuntion param1 param2` )

The part at the left of the equal sign is not valid syntax of course. I\'m just trying to explain what I\'m asking for.

What does work, though, is the following:

array = ( `myBashFuntion param1 param2` )
echo ${array[0]} ${array[1]} ${array[2]}

But an indexed array is not as descriptive as plain variable names.
However, I could just do:

var1 = ${array[0]} ; var2 = ${array[1]} ; var3 = ${array[2]}

But those are 3 more statements that I\'d prefer to avoid.

I\'m just looking for a shortcut syntax. Is it possible?

回答1:

First thing that comes into my mind:

read -r a b c <<<$(echo 1 2 3) ; echo "$a|$b|$c"

output is, unsurprisingly

1|2|3

回答2:

I wanted to assign the values to an array. So, extending Michael Krelin's approach, I did:

read a[{1..3}] <<< $(echo 2 4 6); echo "${a[1]}|${a[2]}|${a[3]}"

which yields:

2|4|6

as expected.

回答3:

I think this might help...

In order to break down user inputted dates (mm/dd/yyyy) in my scripts, I store the day, month, and year into an array, and then put the values into separate variables as follows:

DATE_ARRAY=(`echo $2 | sed -e 's/\// /g'`)
MONTH=(`echo ${DATE_ARRAY[0]}`)
DAY=(`echo ${DATE_ARRAY[1]}`)
YEAR=(`echo ${DATE_ARRAY[2]}`)

回答4:

Sometimes you have to do something funky. Let's say you want to read from a command (the date example by SDGuero for example) but you want to avoid multiple forks.

read month day year << DATE_COMMAND
 $(date "+%m %d %Y")
DATE_COMMAND
echo $month $day $year

You could also pipe into the read command, but then you'd have to use the variables within a subshell:

day=n/a; month=n/a; year=n/a
date "+%d %m %Y" | { read day month year ; echo $day $month $year; }
echo $day $month $year

results in...

13 08 2013
n/a n/a n/a

回答5:

Chapter 5 of the Bash Cookbook by O'Reilly, discusses (at some length) the reasons for the requirement in a variable assignment that there be no spaces around the '=' sign