[apple/shell_cmds.git] / expr / expr.1

.\"	$NetBSD: expr.1,v 1.10 1997/10/20 08:51:56 enami 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 ^ .
.Nm
expects "basic" regular expressions, see 
.Xr re_format 7
for more information on regular expressions.
.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 DIAGNOSTICS
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.
.El
.Sh STANDARDS
The
.Nm
utility conforms to
.St -p1003.2 .
Commit	Line	Data
44bd5ea7 A	1	.\" $NetBSD: expr.1,v 1.10 1997/10/20 08:51:56 enami Exp $
	2	.\"
	3	.\" Written by J.T. Conklin <jtc@netbsd.org>.
	4	.\" Public domain.
	5	.\"
	6	.Dd July 3, 1993
	7	.Dt EXPR 1
	8	.Os
	9	.Sh NAME
	10	.Nm expr
	11	.Nd evaluate expression
	12	.Sh SYNOPSIS
	13	.Nm
	14	.Ar expression
	15	.Sh DESCRIPTION
	16	The
	17	.Nm
	18	utility evaluates
	19	.Ar expression
	20	and writes the result on standard output.
	21	.Pp
	22	All operators are separate arguments to the
	23	.Nm
	24	utility.
	25	Characters special to the command interpreter must be escaped.
	26	.Pp
	27	Operators are listed below in order of increasing precedence.
	28	Operators with equal precedence are grouped within { } symbols.
	29	.Bl -tag -width indent
	30	.It Ar expr1 Li \| Ar expr2
	31	Returns the evaluation of
	32	.Ar expr1
	33	if it is neither an empty string nor zero;
	34	otherwise, returns the evaluation of
	35	.Ar expr2 .
	36	.It Ar expr1 Li & Ar expr2
	37	Returns the evaluation of
	38	.Ar expr1
	39	if neither expression evaluates to an empty string or zero;
	40	otherwise, returns zero.
	41	.It Ar expr1 Li "{=, >, >=, <, <=, !=}" Ar expr2
	42	Returns the results of integer comparison if both arguments are integers;
	43	otherwise, returns the results of string comparison using the locale-specific
	44	collation sequence.
	45	The result of each comparison is 1 if the specified relation is true,
	46	or 0 if the relation is false.
	47	.It Ar expr1 Li "{+, -}" Ar expr2
	48	Returns the results of addition or subtraction of integer-valued arguments.
	49	.It Ar expr1 Li "{*, /, %}" Ar expr2
	50	Returns the results of multiplication, integer division, or remainder of integer-valued arguments.
	51	.It Ar expr1 Li : Ar expr2
	52	The
9bafe280	53	.Dq \&:
44bd5ea7 A	54	operator matches
	55	.Ar expr1
	56	against
	57	.Ar expr2 ,
	58	which must be a regular expression. The regular expression is anchored
	59	to the beginning of the string with an implicit
	60	.Dq ^ .
9bafe280 A	61	.Nm
	62	expects "basic" regular expressions, see
	63	.Xr re_format 7
	64	for more information on regular expressions.
44bd5ea7 A	65	.Pp
	66	If the match succeeds and the pattern contains at least one regular
	67	expression subexpression
	68	.Dq "\e(...\e)" ,
	69	the string corresponding to
	70	.Dq "\e1"
	71	is returned;
	72	otherwise the matching operator returns the number of characters matched.
	73	If the match fails and the pattern contains a regular expression subexpression
	74	the null string is returned;
	75	otherwise 0.
	76	.El
	77	.Pp
	78	Parentheses are used for grouping in the usual manner.
	79	.Sh EXAMPLES
	80	.Bl -enum
	81	.It
	82	The following example adds one to the variable a.
	83	.Dl a=`expr $a + 1`
	84	.It
	85	The following example returns the filename portion of a pathname stored
	86	in variable a. The // characters act to eliminate ambiguity with the
	87	division operator.
	88	.Dl expr "//$a" Li : './\e(.\e)'
	89	.It
	90	The following example returns the number of characters in variable a.
	91	.Dl expr $a Li : '.*'
	92	.El
	93	.Sh DIAGNOSTICS
	94	The
	95	.Nm
	96	utility exits with one of the following values:
	97	.Bl -tag -width Ds -compact
	98	.It 0
	99	the expression is neither an empty string nor 0.
	100	.It 1
	101	the expression is an empty string or 0.
	102	.It 2
	103	the expression is invalid.
	104	.El
	105	.Sh STANDARDS
	106	The
	107	.Nm
	108	utility conforms to
	109	.St -p1003.2 .