Author: jilles Date: Sun Mar 24 22:48:45 2013 New Revision: 248692 URL: http://svnweb.freebsd.org/changeset/base/248692
Log: sh(1): Mention possible ambiguities with $(( and ((. In some other shells, things like $((a);(b)) are command substitutions. Also, there are shells that have an extension ((ARITH)) that evaluates an arithmetic expression and returns status 1 if the result is zero, 0 otherwise. This extension may lead to ambiguity with two subshells starting in sequence. Modified: head/bin/sh/sh.1 Modified: head/bin/sh/sh.1 ============================================================================== --- head/bin/sh/sh.1 Sun Mar 24 22:37:10 2013 (r248691) +++ head/bin/sh/sh.1 Sun Mar 24 22:48:45 2013 (r248692) @@ -32,7 +32,7 @@ .\" from: @(#)sh.1 8.6 (Berkeley) 5/4/95 .\" $FreeBSD$ .\" -.Dd January 22, 2013 +.Dd March 24, 2013 .Dt SH 1 .Os .Sh NAME @@ -1061,6 +1061,9 @@ A subshell environment may be implemente If job control is enabled in an interactive shell, commands grouped in parentheses can be suspended and continued as a unit. .Pp +For compatibility with other shells, +two open parentheses in sequence should be separated by whitespace. +.Pp The second form never forks another shell, so it is slightly more efficient. Grouping commands together this way allows the user to @@ -1618,6 +1621,16 @@ and .Ic times returns information about the same process if they are the only command in a command substitution. +.Pp +If a command substitution of the +.Li $( +form begins with a subshell, +the +.Li $( +and +.Li ( +must be separated by whitespace +to avoid ambiguity with arithmetic expansion. .Ss Arithmetic Expansion Arithmetic expansion provides a mechanism for evaluating an arithmetic expression and substituting its value. _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
