fmlexpr(1F) fmlexpr(1F)
NAME
fmlexpr - evaluate arguments as an expression
SYNOPSIS
fmlexpr arguments
DESCRIPTION
The fmlexpr function evaluates its arguments as an expression. After
evaluation, the result is written on the standard output. Terms of
the expression must be separated by blanks. Characters special to
FMLI must be escaped. Note that 0 is returned to indicate a zero
value, rather than the null string. Strings containing blanks or
other special characters should be quoted. Integer-valued arguments
may be preceded by a unary minus sign. Internally, integers are
treated as 32-bit, 2s complement numbers.
The operators and keywords are listed below. Characters that need to
be escaped are preceded by \. The list is in order of increasing
precedence, with equal precedence operators grouped within {}
symbols.
expr \| expr
returns the first expr if it is neither null nor 0, otherwise
returns the second expr.
expr \& expr
returns the first expr if neither expr is null or 0, otherwise
returns 0.
expr { =, \>, \>=, \<, \<=, != } expr
returns the result of an integer comparison if both arguments
are integers, otherwise returns the result of a lexical
comparison.
expr { +, - } expr
addition or subtraction of integer-valued arguments.
expr { *, /, % } expr
multiplication, division, or remainder of the integer-valued
arguments.
expr : expr
The matching operator : compares the first argument with the
second argument which must be a regular expression. Regular
expression syntax is the same as that of ed(1), except that all
patterns are ``anchored'' (i.e., begin with ^) and, therefore, ^
is not a special character, in that context. Normally, the
matching operator returns the number of bytes matched (0 on
failure). Alternatively, the \(...\) pattern symbols can be
used to return a portion of the first argument.
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fmlexpr(1F) fmlexpr(1F)
EXAMPLES
1. Add 1 to the variable a:
`fmlexpr $a + 1 | set -l a`
2. For $a equal to either "/usr/abc/file" or just "file":
fmlexpr $a : .*/\(.*\) \| $a
returns the last segment of a path name (i.e., file). Watch out for
/ alone as an argument: fmlexpr will take it as the division
operator (see NOTES below).
3. A better representation of example 2.
fmlexpr //$a : .*/\(.*\)
The addition of the // characters eliminates any ambiguity about the
division operator (because it makes it impossible for the left-hand
expression to be interpreted as the division operator), and
simplifies the whole expression.
4. Return the number of characters in $VAR.
fmlexpr $VAR : .*
DIAGNOSTICS
As a side effect of expression evaluation, fmlexpr returns the
following exit values:
0 if the expression is neither null nor 0 (i.e., TRUE)
1 if the expression is null or 0 (i.e., FALSE)
2 for invalid expressions (i.e., FALSE).
syntax error for operator/operand errors
non-numeric argument
if arithmetic is attempted on such a string
In the case of syntax errors and non-numeric arguments, an error
message will be printed at the current cursor position. Use refresh
to redraw the screen.
NOTES
After argument processing by FMLI, fmlexpr cannot tell the difference
between an operator and an operand except by the value. If $a is an
=, the command:
fmlexpr $a = =
looks like:
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fmlexpr(1F) fmlexpr(1F)
fmlexpr = = =
as the arguments are passed to fmlexpr (and they will all be taken as
the = operator). The following works, and returns TRUE:
fmlexpr X$a = X=
SEE ALSO
ed(1), expr(1), set(1F), sh(1).
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