Bash - If then else

About

if execute conditionally a block with a list of command based on the exit status of a list of command

Syntax

if list; then 
list; 
[ elif list; then list; ]... 
[ else list; ] 
fi

• The if list. The command list) is executed (Generally there is one or more conditional command expression in the list of command)
• If its exit status is:
  • zero, then the then list list is executed.
  • Otherwise, each elif list list is executed in turn, and if its exit status is zero:
    • the corresponding then list list is executed and the if command completes.
    • Otherwise, the else list list is executed, if present.

Nested if example

if lists;
then
  ...
else
  if lists;
  then 
     # code if 'expression' is true.
  fi
fi 

Exit Status

The exit status of the entire construct is:

• the exit status of the last command executed,
• or zero if no condition tested true.

Example

With a conditional expression command

if [ "foo" = "foo" ]; then
   echo expression evaluated as true
else
    echo expression evaluated as false
fi

Documentation / Reference

• http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-6.html

help if

• http://mywiki.wooledge.org/BashFAQ/031