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From ed5e4d34a16436a37c0e084666fcfb77cc4859c3 Mon Sep 17 00:00:00 2001 From: Hiltjo Posthuma <hiltjo@codemadness.org> Date: Thu, 31 Jul 2025 14:42:59 +0200 Subject: [PATCH 4/4] improve man pages and some warnings. Checking for warnings: mandoc -Tlint *.1 - Swap .St -p1003.1-2013 macro with text: mdoc does not support this macro and some texts were changed, like commit d4dfd42d3580ad36bedfdc5b8924ff6683981f53 - Typo fixes: exeption -> exception. - xargs.1: document -P extension. - sed.1: remove use of .Pp of .Ss. - Wrap lines to less than 80 characters and use a new sentence for each line. - find.1: Xr reference C library functions.
102 lines
1.7 KiB
Groff
102 lines
1.7 KiB
Groff
.Dd October 8, 2015
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.Dt EXPR 1
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.Os sbase
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.Sh NAME
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.Nm expr
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.Nd evaluate expression
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.Sh SYNOPSIS
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.Nm
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.Ar expression
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.Sh DESCRIPTION
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.Nm
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evaluates
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.Ar expression
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and writes the result to stdout.
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.Pp
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There are two elemental expressions,
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.Sy integer
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and
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.Sy string .
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Let
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.Sy expr
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be a non-elemental expression and
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.Sy expr1 ,
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.Sy expr2
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arbitrary expressions.
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Then
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.Sy expr
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has the recursive form
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.Sy expr = [(] expr1 operand expr2 [)] .
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.Pp
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With
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.Sy operand
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being in order of increasing precedence:
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.Bl -tag -width Ds
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.It |
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Evaluate to
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.Sy expr1
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if it is neither an empty string nor 0; otherwise evaluate to
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.Sy expr2 .
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.It &
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Evaluate to
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.Sy expr1
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if
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.Sy expr1
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and
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.Sy expr2
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are neither empty strings nor 0; otherwise evaluate to 0.
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.It = > >= < <= !=
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If
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.Sy expr1
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and
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.Sy expr2
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are integers, evaluate to 1 if the relation is true and 0 if it is false.
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If
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.Sy expr1
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and
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.Sy expr2
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are strings, apply the relation to the return value of
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.Xr strcmp 3 .
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.It + -
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If
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.Sy expr1
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and
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.Sy expr2
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are integers, evaluate to their sum or subtraction.
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.It * / %
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If
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.Sy expr1
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and
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.Sy expr2
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are integers, evaluate to their multiplication, division or remainder.
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.It :
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Evaluate to the number of characters matched in
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.Sy expr1
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against
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.Sy expr2 . expr2
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is anchored with an implicit '^'.
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.Pp
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You can't directly match the empty string, since zero matched characters
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resolve equally to a failed match.
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To work around this limitation, use "expr X'' : 'X$' instead of "expr ''
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: '$'"
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.El
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.Sh EXIT STATUS
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.Bl -tag -width Ds
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.It 0
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.Ar expression
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is neither an empty string nor 0.
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.It 1
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.Ar expression
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is an empty string or 0.
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.It 2
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.Ar expression
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is invalid.
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.It > 2
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An error occurred.
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.El
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.Sh SEE ALSO
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.Xr test 1
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.Sh STANDARDS
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POSIX.1-2013.
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