108 lines
2.8 KiB
Groff
108 lines
2.8 KiB
Groff
.\" $NetBSD: expr.1,v 1.12 2000/08/28 02:11:05 hubertf Exp $
|
|
.\"
|
|
.\" Written by J.T. Conklin <jtc@netbsd.org>.
|
|
.\" Public domain.
|
|
.\"
|
|
.Dd July 3, 1993
|
|
.Dt EXPR 1
|
|
.Os
|
|
.Sh NAME
|
|
.Nm expr
|
|
.Nd evaluate expression
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Ar expression
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
utility evaluates
|
|
.Ar expression
|
|
and writes the result on standard output.
|
|
.Pp
|
|
All operators are separate arguments to the
|
|
.Nm
|
|
utility.
|
|
Characters special to the command interpreter must be escaped.
|
|
.Pp
|
|
Operators are listed below in order of increasing precedence.
|
|
Operators with equal precedence are grouped within { } symbols.
|
|
.Bl -tag -width indent
|
|
.It Ar expr1 Li | Ar expr2
|
|
Returns the evaluation of
|
|
.Ar expr1
|
|
if it is neither an empty string nor zero;
|
|
otherwise, returns the evaluation of
|
|
.Ar expr2 .
|
|
.It Ar expr1 Li & Ar expr2
|
|
Returns the evaluation of
|
|
.Ar expr1
|
|
if neither expression evaluates to an empty string or zero;
|
|
otherwise, returns zero.
|
|
.It Ar expr1 Li "{=, >, >=, <, <=, !=}" Ar expr2
|
|
Returns the results of integer comparison if both arguments are integers;
|
|
otherwise, returns the results of string comparison using the locale-specific
|
|
collation sequence.
|
|
The result of each comparison is 1 if the specified relation is true,
|
|
or 0 if the relation is false.
|
|
.It Ar expr1 Li "{+, -}" Ar expr2
|
|
Returns the results of addition or subtraction of integer-valued arguments.
|
|
.It Ar expr1 Li "{*, /, %}" Ar expr2
|
|
Returns the results of multiplication, integer division, or remainder of integer-valued arguments.
|
|
.It Ar expr1 Li : Ar expr2
|
|
The
|
|
.Dq \:
|
|
operator matches
|
|
.Ar expr1
|
|
against
|
|
.Ar expr2 ,
|
|
which must be a regular expression. The regular expression is anchored
|
|
to the beginning of the string with an implicit
|
|
.Dq ^ .
|
|
.Pp
|
|
If the match succeeds and the pattern contains at least one regular
|
|
expression subexpression
|
|
.Dq "\e(...\e)" ,
|
|
the string corresponding to
|
|
.Dq "\e1"
|
|
is returned;
|
|
otherwise the matching operator returns the number of characters matched.
|
|
If the match fails and the pattern contains a regular expression subexpression
|
|
the null string is returned;
|
|
otherwise 0.
|
|
.El
|
|
.Pp
|
|
Parentheses are used for grouping in the usual manner.
|
|
.Sh EXAMPLES
|
|
.Bl -enum
|
|
.It
|
|
The following example adds one to the variable a.
|
|
.Dl a=`expr $a + 1`
|
|
.It
|
|
The following example returns the filename portion of a pathname stored
|
|
in variable a. The // characters act to eliminate ambiguity with the
|
|
division operator.
|
|
.Dl expr "//$a" Li : '.*/\e(.*\e)'
|
|
.It
|
|
The following example returns the number of characters in variable a.
|
|
.Dl expr $a Li : '.*'
|
|
.El
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Nm
|
|
utility exits with one of the following values:
|
|
.Bl -tag -width Ds -compact
|
|
.It 0
|
|
the expression is neither an empty string nor 0.
|
|
.It 1
|
|
the expression is an empty string or 0.
|
|
.It 2
|
|
the expression is invalid.
|
|
.It >2
|
|
an error occurred (such as memory allocation failure).
|
|
.El
|
|
.Sh STANDARDS
|
|
The
|
|
.Nm
|
|
utility conforms to
|
|
.St -p1003.2 .
|