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<A NAME="PAGENUM-34"><P>Page 34</P></A>
<P>
<B>MODIFIERS</B>
</P>
<P>After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a
:</P>
<TABLE>
<TR><TD>
h
</TD><TD>
Remove a trailing pathname component, leaving only the head.
</TD></TR><TR><TD>
r
</TD><TD>
Remove a trailing suffix of the form .xxx, leaving the basename.
</TD></TR><TR><TD>
e
</TD><TD>
Remove all but the trailing suffix.
</TD></TR><TR><TD>
t
</TD><TD>
Remove all leading pathname components, leaving the tail.
</TD></TR><TR><TD>
p
</TD><TD>
Print the new command but do not execute it.
</TD></TR><TR><TD>
q
</TD><TD>
Quote the substituted words, escaping further substitutions.
</TD></TR><TR><TD>
x
</TD><TD>
Quote the substituted words as with q, but break into words at blanks and newlines.
</TD></TR><TR><TD>
s/old/new/
</TD><TD>
Substitute new for the first occurrence of
old in the event line. Any delimiter can be used in place
of /. The final delimiter is optional if it is the last character of the event line. The delimiter may
be quoted in old and new with a single backslash.
If & appears in new, it is replaced by old. A
single backslash will quote the &.
</TD></TR><TR><TD>
&
</TD><TD>
Repeat the previous substitution.
</TD></TR><TR><TD>
g
</TD><TD>
Cause changes to be applied over the entire event line. This is used in conjunction with
:s (for example, :gs/old/new/) or :&. If used with
:s, any delimiter can be used in place of /, and the
final delimiter is optional if it is the last character of the event line.
</TD></TR></TABLE>
<B>
<P>ARITHMETIC EVALUATION</P>
</B>
<P>The shell allows arithmetic expressions to be evaluated, under certain circumstances. (See the
let built-in command and "Arithmetic Expansion.") Evaluation is done in long integers with no check for overflow, though division by 0 is trapped
and flagged as an error. The following list of operators is grouped into levels of equal-precedence operators. The levels are
listed in order of decreasing precedence.</P>
<TABLE>
<TR><TD>
_ +
</TD><TD>
Unary minus and plus
</TD></TR><TR><TD>
! ~
</TD><TD>
Logical and bitwise negation
</TD></TR><TR><TD>
* / %
</TD><TD>
Multiplication, division, remainder
</TD></TR><TR><TD>
+ _
</TD><TD>
Addition, subtraction
</TD></TR><TR><TD>
<< >>
</TD><TD>
Left and right bitwise shifts
</TD></TR><TR><TD>
<= >= <>
</TD><TD>
Comparison
</TD></TR><TR><TD>
== !=
</TD><TD>
Equality and inequality
</TD></TR><TR><TD>
&
</TD><TD>
Bitwise AND
</TD></TR><TR><TD>
^
</TD><TD>
Bitwise exclusive OR
</TD></TR><TR><TD>
| Bitwise OR
</TD><TD>
&&
</TD></TR><TR><TD>
Logical AND
</TD><TD>
||
</TD></TR><TR><TD>
Logical OR
</TD><TD>
= *= /= %= += _= <<= >>=&=^=|=
</TD></TR><TR><TD>
Assignment
</TD></TR></TABLE>
<P>Shell variables are allowed as operands; parameter expansion is performed before the expression is evaluated. The value of
a parameter is coerced to a long integer within an expression. A shell variable need not have its integer attribute turned on
to be used in an expression.</P>
<P>Constants with a leading 0 are interpreted as octal numbers. A leading
0x or 0X denotes hexadecimal. Otherwise, numbers take the form
[base#]n, where base is a decimal number between 2 and 36 representing the arithmetic base, and
n is a number in that base. If base is omitted, then base 10 is used.</P>
<P>Operators are evaluated in order of precedence. Subexpressions in parentheses are evaluated first and may override
the precedence rules.</P>
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