Editing C shell (section)

=== Expressions ===

The C shell implements a 32-bit integer expression grammar with operators borrowed from C but with a few additional operators for string comparisons and filesystem tests, e.g., testing for the existence of a file.  Operators must be separated by whitespace from their operands.  Variables are referenced as <code>$</code>''name''.

[[Operator precedence#Programming languages|Operator precedence]] is also borrowed from C, but with different [[operator associativity]] rules to resolve the ambiguity of what comes first in a sequence of equal precedence operators.  In C, the associativity is left-to-right for most operators; in C shell, it is right-to-left.  For example,

{{column
|width=60em
|1=
<syntaxhighlight lang="c">
// C groups from the left
int i = 10 / 5 * 2;
printf( "%d\n", i ); // prints 4
i = 7 - 4 + 2;
printf( "%d\n", i ); // prints 5
i = 2 >> 1 << 4;
printf( "%d\n", i ); // prints 16
</syntaxhighlight>
|2=
<syntaxhighlight lang="csh">
# C shell groups from the right
@ i = 10 / 5 * 2
echo $i # prints 1
@ i = 7 - 4 + 2
echo $i # prints 1
@ i = ( 2 >> 1 << 4 )
echo $i # prints 0
</syntaxhighlight>
}}

The parentheses in the C shell example are to avoid having the bit-shifting operators confused as I/O redirection operators.  In either language, parentheses can always be used to explicitly specify the desired order of evaluation, even if only for clarity.

Return values are limited to 8-bit. For <code>exit</code> expressions, the unary negation operator can be used for 32-bit evaluation.

<syntaxhighlight lang="csh">
exit ! ! 256 # Returns 1.
</syntaxhighlight>