Bash * and @ Relative to Array Elements: Difference between revisions

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</syntaxhighlight>
</syntaxhighlight>


=<tt>...@</tt>=
The behavior in case of getting indexed array values or associative array keys or values, is similar:


=<tt>"...@"</tt>=
<syntaxhighlight lang='bash'>
declare -a some_array
some_array[0]="A B"
some_array[1]="C D"
for i in ${some_array[*]}; do
  echo ${i}
done
</syntaxhighlight>
outputs:
<syntaxhighlight lang='bash'>
A
B
C
D
</syntaxhighlight>
 
=<tt>"@"</tt>=
 
=<tt>@</tt>=
Using <code>@</code> without double-quote enclosure to iterate over array elements is signaled as an error by bash static syntax checkers:

Revision as of 18:56, 1 April 2024

Internal

Overview

* and @ are bash syntax elements that tokenize arrays. They are used to process command line argument ($*, $@ and "$@"), values for indexed arrays, keys and values for associative arrays, etc.

The difference between these two syntax elements becomes apparent when the array elements contain spaces:

*

Each element in the array is represented as an individual string. The arguments that contain spaces are tokenized, and the spaces are discarded. In other words, the arguments that contain spaces are not joined together, but handled as different tokens.

In case of command line arguments handled as such:

for i in $*; do
  echo ${i}
done

calling the program with:

./test.sh "A B" "C D"

outputs:

A
B
C
D

The behavior in case of getting indexed array values or associative array keys or values, is similar:

declare -a some_array
some_array[0]="A B"
some_array[1]="C D"
for i in ${some_array[*]}; do
  echo ${i}
done

outputs:

A
B
C
D

"@"

@

Using @ without double-quote enclosure to iterate over array elements is signaled as an error by bash static syntax checkers: