if(1)                                                             if(1)

  if

  NAME

    if - execute commands if expression is true

  SYNOPSIS

  C shell

    if (expr) command

    if (expr) then
    ...
    else if (expr2) then
    ...
    else
    ...
    endif

  Korn shell

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

  DESCRIPTION

    This command is a built-in command in the C shell and the Korn shell.

  C shell

    For the first form, if expr (an expression, as described in the tcsh(1)
    section on Expressions) evaluates true, command is executed. Variable
    substitution on command occurs early, at the same time as it does for the
    rest of the if command. The command argument must be a simple command, not
    an alias, a pipeline, a command list, or a parenthesized command list. It
    can have arguments. Input/output redirection occurs even if expr is false
    and command is thus not executed; this is a bug.

    For the second form, if the specified expr is true, the commands to the
    first else are executed. Otherwise, if expr2 is true, the commands to the
    second else are executed, and so on. Any number of else-if pairs are
    possible; only one endif is needed. The else part is optional. The words
    else and endif must appear at the beginning of input lines. The if must
    appear alone on its input line or after an else.)

  Korn shell

    If the exit status of the first list is zero, the second list is executed;
    otherwise the list following the elif, if any, is executed with similar
    consequences. If all the lists following the if and each elif fail (that
    is, exit with non-zero status), the list following the else is executed.
    The exit status of an if statement is that of nonconditional list that is
    executed. If no nonconditional list is executed, the exit status is zero.