02. Quotes review "", '', ``

Let's do a quick review on the two types of quotation marks and back tick before we move on.

Quotation marks

Here's a quick recap of the differences between the two quotation marks. Head over to our Command Line series lesson for a more in-detailed look.

Single quotes ''
Literal values.
Guarantee shell won't try substitutions.
Double quotes ""
Before running the command, shell looks for variables, globs and other substitutions to perform.
More flexibility with the shell.
Executes everything literally except for $, \, ! or `.
Back quotes ``
Key found on top of left tab key.
Used to execute commands.
$ echo $123
# Evaluates $1 as positional parameter
23
$ echo "$123"
# Same as above
23
$ echo '$123'
# Literal output
$123
$ printf "Today's calendar: \n`cal`"
Today's calendar:
     July 2015
Su Mo Tu We Th Fr Sa
          1  2  3  4
 5  6  7  8  9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31:

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