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Add mandoc-manpage for expr(1)

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and mark it as finished in README.
Upon further checking, expr(1) turns out to be implicitly UTF-8 compliant.
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FRIGN 2015-01-25 16:49:46 +01:00
parent 1a8dfaca37
commit b98bf41ecc
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README
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@ -29,7 +29,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
=* echo yes none
=* env yes none
#* expand yes none
expr yes none
=* expr yes none
=* false yes none
fold yes none
grep yes none

207
expr.1
View File

@ -1,12 +1,5 @@
.\" $OpenBSD: src/bin/expr/expr.1,v 1.22 2014/02/23 18:13:27 schwarze Exp $
.\" $NetBSD: expr.1,v 1.9 1995/04/28 23:27:13 jtc Exp $
.\"
.\" Written by J.T. Conklin <jtc@netbsd.org>.
.\" Public domain.
.\"
.Dd $Mdocdate: September 3 2010 $
.Dt EXPR 1
.Os
.Dd January 25, 2015
.Dt EXPR 1 sbase\-VERSION
.Sh NAME
.Nm expr
.Nd evaluate expression
@ -14,143 +7,95 @@
.Nm expr
.Ar expression
.Sh DESCRIPTION
The
.Nm
utility evaluates
evaluates
.Ar expression
and writes the result on standard output.
All operators are separate arguments to the
.Nm
utility.
Characters special to the command interpreter must be escaped.
and writes the result to stdout.
.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 | 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
.Ql \&:
operator matches
.Ar expr1
There are two elemental expressions,
.Sy integer
and
.Sy string.
Let
.Sy expr
be a non-elemental expression and
.Sy expr1 ,
.Sy expr2
arbitrary expressions. Then
.Sy expr
has the recursive form
.Sy expr = [(] expr1 operand expr2 [)].
.Pp
With
.Sy operand
being in oder of increasing precedence:
.Bl -tag -width Ds
.It |
Evaluate to
.Sy expr1
if it is neither an empty string nor 0; otherwise evaluate to
.Sy expr2 .
.It &
Evaluate to
.Sy expr1
if
.Sy expr1
and
.Sy expr2
are neither empty strings nor 0; otherwise evaluate to 0.
.It = > >= < <= !=
If
.Sy expr1
and
.Sy expr2
are integers, evaluate to 1 if the relation is true and 0 if it is false.
If
.Sy expr1
and
.Sy expr2
are strings, apply the relation to the return value of
.Xr strcmp 3 .
.It + -
If
.Sy expr1
and
.Sy expr2
are integers, evaluate to their sum or subtraction.
.It * / %
If
.Sy expr1
and
.Sy expr2
are integers, evaluate to their mulitplication, division or remainder.
.It :
Evaluate to the number of characters matched in
.Sy expr1
against
.Ar expr2 ,
which must be a basic regular expression.
The regular expression is anchored
to the beginning of the string with an implicit
.Ql ^ .
.Sy expr2 . expr2
is anchored with an implicit '^'.
.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, returns 0.
.Pp
Note: the empty string cannot be matched using
.Bd -literal -offset indent
expr '' : '$'
.Ed
.Pp
This is because the returned number of matched characters
.Pq zero
is indistinguishable from a failed match, so
.Nm
returns failure
.Pq 0 .
To match the empty string, use a structure such as:
.Bd -literal -offset indent
expr X'' : 'X$'
.Ed
You can't directly match the empty string, since zero matched characters
resolve equally to a failed match. To work around this limitation, use "expr X'' : 'X$' instead of "expr '' : '$'"
.El
.Pp
Parentheses are used for grouping in the usual manner.
.Sh EXIT STATUS
The
.Nm
utility exits with one of the following values:
.Pp
.Bl -tag -width Ds -offset indent -compact
.Bl -tag -width Ds
.It 0
The expression is neither an empty string nor 0.
.Ar expression
is neither an empty string nor 0
.It 1
The expression is an empty string or 0.
.Ar expression
is an empty string or 0
.It 2
The expression is invalid.
.It \*(Gt2
An error occurred (such as memory allocation failure).
.Ar expression
is invalid
.It > 2
An error occured
.El
.Sh EXAMPLES
Add 1 to the variable
.Va a :
.Bd -literal -offset indent
$ a=`expr $a + 1`
.Ed
.Pp
Return the filename portion of a pathname stored
in variable
.Va a .
The
.Ql //
characters act to eliminate ambiguity with the division operator:
.Bd -literal -offset indent
$ expr "//$a" \&: '.*/\e(.*\e)'
.Ed
.Pp
Return the number of characters in variable
.Va a :
.Bd -literal -offset indent
$ expr $a \&: '.*'
.Ed
.Sh SEE ALSO
.Xr test 1 ,
.Xr re_format 7
.Xr test 1
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2008
specification.
.Sh HISTORY
The
.Nm
utility first appeared in the Programmer's Workbench (PWB/UNIX)
and has supported regular expressions since
.At v7 .
It was rewritten from scratch for
.Bx 386 0.1
and again for
.Nx 1.1 .
.Sh AUTHORS
.An -nosplit
The first free version was written by
.An Pace Willisson
in 1992.
This version was written by
.An John T. Conklin
in 1994.