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Chet Ramey
2017-03-28 11:32:59 -04:00
parent f698849a75
commit 124d67cde0
41 changed files with 9975 additions and 9249 deletions
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@@ -5,12 +5,12 @@
.\" Case Western Reserve University
.\" chet.ramey@case.edu
.\"
.\" Last Change: Mon Mar 13 12:04:35 EDT 2017
.\" Last Change: Wed Mar 22 15:35:08 EDT 2017
.\"
.\" bash_builtins, strip all but Built-Ins section
.if \n(zZ=1 .ig zZ
.if \n(zY=1 .ig zY
.TH BASH 1 "2017 March 13" "GNU Bash 4.4"
.TH BASH 1 "2017 March 22" "GNU Bash 4.4"
.\"
.\" There's some problem with having a `@'
.\" in a tagged paragraph with the BSD man macros.
@@ -2673,10 +2673,12 @@ special parameters \fI@\fP and \fI*\fP within double quotes.
The
.B unset
builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
destroys the array element at index \fIsubscript\fP.
destroys the array element at index \fIsubscript\fP,
for both indexed and associative arrays.
Negative subscripts to indexed arrays are interpreted as described above.
Care must be taken to avoid unwanted side effects caused by pathname
expansion.
Unsetting the last element of an array variable does not unset the variable.
\fBunset\fP \fIname\fP, where \fIname\fP is an array, or
\fBunset\fP \fIname\fP[\fIsubscript\fP], where
\fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
@@ -4244,6 +4246,42 @@ Variables local to the function may be declared with the
.B local
builtin command. Ordinarily, variables and their values
are shared between the function and its caller.
If a variable is declared \fBlocal\fP, the variable's visible scope
is restricted to that function and its children (including the functions
it calls).
Local variables "shadow" variables with the same name declared at
previous scopes.
For instance, a local variable declared in a function
hides a global variable of the same name: references and assignments
refer to the local variable, leaving the global variable unmodified.
When the function returns, the global variable is once again visible.
.PP
The shell uses \fIdynamic scoping\fP to control a variable's visibility
within functions.
With dynamic scoping, visible variables and their values
are a result of the sequence of function calls that caused execution
to reach the current function.
The value of a variable that a function sees depends
on its value within its caller, if any, whether that caller is
the "global" scope or another shell function.
This is also the value that a local variable
declaration "shadows", and the value that is restored when the function
returns.
.PP
For example, if a variable \fIvar\fP is declared as local in function
\fIfunc1\fP, and \fIfunc1\fP calls another function \fIfunc2\fP,
references to \fIvar\fP made from within \fIfunc2\fP will resolve to the
local variable \fIvar\fP from \fIfunc1\fP, shadowing any global variable
named \fIvar\fP.
.PP
The \fBunset\fP builtin also acts using the same dynamic scope: if a
variable is local to the current scope, \fBunset\fP will unset it;
otherwise the unset will refer to the variable found in any calling scope
as described above.
If a variable at the local scope is unset, it will remain so
until it is reset in that scope or until the function returns.
If the unset acts on a variable at a previous scope, any instance of a
variable with that name that had been shadowed will become visible.
.PP
The \fBFUNCNEST\fP variable, if set to a numeric value greater
than 0, defines a maximum function nesting level. Function