Echo newline com aspas [duplicado]

Question

Para:

$hello="hello
> world"

Por que echo não imprime a nova linha para:

echo -e $hello

Mas se eu colocar $hello entre aspas, isso acontece.

$ echo "$hello"
hello
world

Isso é devido a citações ANSI-C? Não deve echo -e interpretar a nova linha que eu inseri?

    

Answer 1

Na página bash man, isso descreve como a divisão de palavras é feita de acordo com o conteúdo da variável IFS :

Word Splitting

The shell scans the results of parameter expansion, command substitution, and arithmetic expansion that did not occur within double quotes for word splitting.

The shell treats each character of IFS as a delimiter, and splits the results of the other expansions into words using these characters as field terminators. If IFS is unset, or its value is exactly <space><tab><newline>, the default, then sequences of <space>, <tab>, and <newline> at the beginning and end of the results of the previous expansions are ignored, and any sequence of IFS characters not at the beginning or end serves to delimit words. If IFS has a value other than the default, then sequences of the whitespace characters space and tab are ignored at the beginning and end of the word, as long as the whitespace character is in the value of IFS (an IFS whitespace character). Any character in IFS that is not IFS whitespace, along with any adjacent IFS whitespace characters, delimits a field. A sequence of IFS whitespace characters is also treated as a delimiter. If the value of IFS is null, no word splitting occurs.

Explicit null arguments ("" or '') are retained. Unquoted implicit null arguments, resulting from the expansion of parameters that have no values, are removed. If a parameter with no value is expanded within double quotes, a null argument results and is retained.

Note that if no expansion occurs, no splitting is performed.

bash divide a palavra em sua variável se ela não for duplicada, então hello e world se tornam dois argumentos diferentes para echo . echo coloca um espaço entre os argumentos.