1

For:

$hello="hello
> world"

Why does echo not print the newline for:

echo -e $hello

But if I put $hello in quotes it does. 

$ echo "$hello"
hello
world

Is this because of ANSI-C Quoting? Shouldn't echo -e interpret the newline I inputted?

Quaxton Hale
  • 317
  • It's because of trailing newlines. – DisplayName Dec 30 '14 at 18:34
  • $hello without the quotes undergoes shell splitting. – muru Dec 30 '14 at 18:40
  • EngieOP - please search the site for terms like whitespace and/or $IFS - this is covered exhaustively elsewhere. @DisplayName - this doesn't, in fact, have much to do with trailing \newlines but is rather a result of the shell's default split configuration on its Internal Field Separator. And also echo's handling of arguments - it concatenates them on spaces. – mikeserv Dec 30 '14 at 18:40
  • @Nasha - that's not true, exactly. They're not spaces - echo does that - they're \000 NULs. They're separate fields. – mikeserv Dec 30 '14 at 18:43
  • @mikeserv: woops, didn't see your comment, thanks for filling my voids :) . –  Dec 30 '14 at 18:47

1 Answers1

1

From the bash man page, this describes how word splitting is done according the contents of the IFS variable:

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 does word splitting on your variable if it is not double quoted so hello and world become two different arguments to echo. echo puts a space between arguments.

Graeme
  • 34,027