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NAME            if --  conditional command
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SYNOPSIS        if\b\b__ expr command [ arg\e91\e8 ... ]
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DESCRIPTION     if\b\b__
evaluates the expression expr\b\b\b\b____, and if its value is true\b\b\b\b____,
executes the given command\b\b\b\b\b\b\b_______ with the given arguments.

The following primitives are used to construct
the expr\b\b\b\b____:

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-r\b\b__ file
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true if the file exists and is readable.

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-w\b\b__ file
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true if the file exists and is writable

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s1 =\b_ s2
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true if the strings s1\b\b__ and s2\b\b__ are equal.

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s1 !=\b\b__ s2
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true if the strings s1\b\b__ and s2\b\b__ are not equal.

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These primaries may be combined with the
following operators:

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!\b_
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unary negation operator

-a\b\b__
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binary and\b\b\b___ operator

-o\b\b__
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binary or\b\b__ operator

(\b_ expr )\b_
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parentheses for grouping.

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-a\b\b__ has higher precedence than -o\b\b__.
Notice that all the operators and flags are separate
arguments to if\b\b__ and hence must be surrounded by spaces.
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FILES           --
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SEE ALSO        sh(I)
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DIAGNOSTICS     "if error",
if the expression has the wrong syntax;
"command not found."
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BUGS            --