Quoting (cont)
Single-quotes are useful to pass shell meta-characters in args:
e.g. grep 'S.*[0-9]+$' < myfile
Use double-quotes to
- construct strings using the values of shell variables
e.g. "x=$x, y=$y" like Java's ("x=" + x + ", y=" + y)
- prevent empty variables from "vanishing"
e.g. use test "$x" = "abc" rather than test $x = "abc" in case $x is empty
- for values obtained from the command line or a user
e.g. use test -f " $1" rather than test -f $1 in case
$1 contains a path with spaces (e.g. C:/Program Files/app/data
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