3

I don't understand why this doesn't work:

TEXT="blah" echo $TEXT    #echoes nothing

I thought it might be because echo is a builtin, so I tried this:

TEXT="blah" `which echo` $TEXT    #still nothing

What am I missing?

4

The shell expands the variables before it runs the command, even before it runs the assignments.

Cf.

text=blah ; echo $text

or

text=blah eval 'echo $text'

The first one works because the assignment is run as a separate command. The second one works because $text is single-quoted which prevents its expansion when shell is processing the command; when eval is later running, the variable already has the value assigned.

2
  • OK, I see. So if TEXT had been "foo" beforehand, TEXT="blah" echo $TEXT would have been expanded to TEXT="blah" echo foo before being executed.
    – Simonski
    Oct 31 '18 at 13:23
  • Exactly, and it's very easy to try: text=blah; text=new echo $text.
    – choroba
    Oct 31 '18 at 14:42

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