Date: Thu, 9 Sep 2010 21:59:54 +0000 (UTC) From: Jilles Tjoelker <jilles@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r212390 - head/bin/expr Message-ID: <201009092159.o89LxsHf038447@svn.freebsd.org>
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Author: jilles Date: Thu Sep 9 21:59:53 2010 New Revision: 212390 URL: http://svn.freebsd.org/changeset/base/212390 Log: expr(1): Add sh(1) versions of examples, remove an incorrect example. The three examples are better done using sh(1) itself these days. The example expr -- "$a" : ".*" is incorrect in the general case, as "$a" may be an operator. MFC after: 2 weeks Modified: head/bin/expr/expr.1 Modified: head/bin/expr/expr.1 ============================================================================== --- head/bin/expr/expr.1 Thu Sep 9 21:39:06 2010 (r212389) +++ head/bin/expr/expr.1 Thu Sep 9 21:59:53 2010 (r212390) @@ -30,7 +30,7 @@ .\" .\" $FreeBSD$ .\" -.Dd July 12, 2004 +.Dd September 9, 2010 .Dt EXPR 1 .Os .Sh NAME @@ -217,6 +217,9 @@ command, one might rearrange the express More generally, parenthesize possibly-negative values: .Dl "a=$(expr \e( $a \e) + 1)" .It +With shell arithmetic, no escaping is required: +.Dl "a=$((a + 1))" +.It This example prints the filename portion of a pathname stored in variable .Va a . @@ -229,6 +232,12 @@ The .Li // characters resolve this ambiguity. .Dl "expr \*q//$a\*q \&: '.*/\e(.*\e)'" +.It +With modern +.Xr sh 1 +syntax, +.Dl "\*q${a##*/}\*q" +expands to the same value. .El .Pp The following examples output the number of characters in variable @@ -237,19 +246,21 @@ Again, if .Va a might begin with a hyphen, it is necessary to prevent it from being interpreted as an option to -.Nm . +.Nm , +and +.Va a +might be interpreted as an operator. .Bl -bullet .It -If the -.Nm -command conforms to -.St -p1003.1-2001 , -this is simple: -.Dl "expr -- \*q$a\*q \&: \*q.*\*q" -.It -For portability to older systems, however, a more complicated command +To deal with all of this, a complicated command is required: .Dl "expr \e( \*qX$a\*q \&: \*q.*\*q \e) - 1" +.It +With modern +.Xr sh 1 +syntax, this can be done much more easily: +.Dl "${#a}" +expands to the required number. .El .Sh SEE ALSO .Xr sh 1 ,
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