4.2. Variable Assignment

Do not confuse this with = and -eq, which test, rather than assign!

Note that = can be either an assignment or a test operator, depending on context.

 1 #!/bin/bash
 2 # Naked variables
 3 
 4 echo
 5 
 6 # When is a variable "naked", i.e., lacking the '$' in front?
 7 # When it is being assigned, rather than referenced.
 8 
 9 # Assignment
 10 a=879
 11 echo "The value of \"a\" is $a."
 12 
 13 # Assignment using 'let'
 14 let a=16+5
 15 echo "The value of \"a\" is now $a."
 16 
 17 echo
 18 
 19 # In a 'for' loop (really, a type of disguised assignment)
 20 echo -n "Values of \"a\" in the loop are: "
 21 for a in 7 8 9 11
 22 do
 23 echo -n "$a "
 24 done
 25 
 26 echo
 27 echo
 28 
 29 # In a 'read' statement (also a type of assignment)
 30 echo -n "Enter \"a\" "
 31 read a
 32 echo "The value of \"a\" is now $a."
 33 
 34 echo
 35 
 36 exit 0

 1 #!/bin/bash
 2 
 3 a=23 # Simple case
 4 echo $a
 5 b=$a
 6 echo $b
 7 
 8 # Now, getting a little bit fancier (command substitution).
 9 
 10 a=`echo Hello!` # Assigns result of 'echo' command to 'a'
 11 echo $a
 12 # Note that using an exclamation mark (!) in command substitution
 13 #+ will not work from the command line,
 14 #+ since this triggers the Bash "history mechanism."
 15 # Within a script, however, the history functions are disabled.
 16 
 17 a=`ls -l` # Assigns result of 'ls -l' command to 'a'
 18 echo $a # Unquoted, however, removes tabs and newlines.
 19 echo
 20 echo "$a" # The quoted variable preserves whitespace.
 21 # (See the chapter on "Quoting.")
 22 
 23 exit 0