mirror of
https://https.git.savannah.gnu.org/git/bash.git
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bash-5.2-beta release
This commit is contained in:
Chet Ramey
+116
-41
@@ -4,13 +4,13 @@
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<!-- This text is a brief description of the features that are present in
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the Bash shell (version 5.2, 26 December 2021).
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the Bash shell (version 5.2, 24 February 2022).
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This is Edition 5.2, last updated 26 December 2021,
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This is Edition 5.2, last updated 24 February 2022,
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of The GNU Bash Reference Manual,
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for Bash, Version 5.2.
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Copyright (C) 1988-2021 Free Software Foundation, Inc.
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Copyright (C) 1988-2022 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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@@ -77,10 +77,10 @@ Next: <a href="#Introduction" accesskey="n" rel="next">Introduction</a>, Previou
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<span id="Bash-Features-1"></span><h1 class="top">Bash Features</h1>
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<p>This text is a brief description of the features that are present in
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the Bash shell (version 5.2, 26 December 2021).
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the Bash shell (version 5.2, 24 February 2022).
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The Bash home page is <a href="http://www.gnu.org/software/bash/">http://www.gnu.org/software/bash/</a>.
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</p>
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<p>This is Edition 5.2, last updated 26 December 2021,
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<p>This is Edition 5.2, last updated 24 February 2022,
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of <cite>The GNU Bash Reference Manual</cite>,
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for <code>Bash</code>, Version 5.2.
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</p>
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@@ -1947,10 +1947,22 @@ return status is the exit status of the last command executed
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before the <code>return</code>.
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</p>
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<p>Variables local to the function may be declared with the
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<code>local</code> builtin. These variables are visible only to
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<code>local</code> builtin (<em>local variables</em>).
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Ordinarily, variables and their values
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are shared between a function and its caller.
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These variables are visible only to
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the function and the commands it invokes. This is particularly
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important when a shell function calls other functions.
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</p>
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<p>In the following description, the <em>current scope</em> is a currently-
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executing function.
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Previous scopes consist of that function’s caller and so on,
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back to the "global" scope, where the shell is not executing
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any shell function.
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Consequently, a local variable at the current local scope is a variable
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declared using the <code>local</code> or <code>declare</code> builtins in the
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function that is currently executing.
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</p>
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<p>Local variables "shadow" variables with the same name declared at
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previous scopes. For instance, a local variable declared in a function
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hides a global variable of the same name: references and assignments
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@@ -2003,11 +2015,13 @@ variable is local to the current scope, <code>unset</code> will unset it;
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otherwise the unset will refer to the variable found in any calling scope
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as described above.
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If a variable at the current local scope is unset, it will remain so
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(appearing as unset)
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until it is reset in that scope or until the function returns.
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Once the function returns, any instance of the variable at a previous
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scope will become visible.
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If the unset acts on a variable at a previous scope, any instance of a
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variable with that name that had been shadowed will become visible.
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variable with that name that had been shadowed will become visible
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(see below how <code>localvar_unset</code>shell option changes this behavior).
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</p>
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<p>Function names and definitions may be listed with the
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<samp>-f</samp> option to the <code>declare</code> (<code>typeset</code>)
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@@ -2608,7 +2622,7 @@ var is set and not null
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<dd><p>This is referred to as Substring Expansion.
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It expands to up to <var>length</var> characters of the value of <var>parameter</var>
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starting at the character specified by <var>offset</var>.
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If <var>parameter</var> is ‘<samp>@</samp>’, an indexed array subscripted by
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If <var>parameter</var> is ‘<samp>@</samp>’ or ‘<samp>*</samp>’, an indexed array subscripted by
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‘<samp>@</samp>’ or ‘<samp>*</samp>’, or an associative array name, the results differ as
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described below.
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If <var>length</var> is omitted, it expands to the substring of the value of
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@@ -2683,8 +2697,8 @@ bc
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$ echo ${array[0]: -7:-2}
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bcdef
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</pre>
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<p>If <var>parameter</var> is ‘<samp>@</samp>’, the result is <var>length</var> positional
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parameters beginning at <var>offset</var>.
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<p>If <var>parameter</var> is ‘<samp>@</samp>’ or ‘<samp>*</samp>’, the result is <var>length</var>
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positional parameters beginning at <var>offset</var>.
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A negative <var>offset</var> is taken relative to one greater than the greatest
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positional parameter, so an offset of -1 evaluates to the last positional
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parameter.
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@@ -2845,45 +2859,65 @@ and the ‘<samp>/</samp>’ following <var>pattern</var> may be omitted
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any unquoted instances of ‘<samp>&</samp>’ in <var>string</var> are replaced with the
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matching portion of <var>pattern</var>.
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This is intended to duplicate a common <code>sed</code> idiom.
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Backslash is used to quote ‘<samp>&</samp>’ in <var>string</var>; the backslash is removed
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</p>
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<p>Quoting any part of <var>string</var> inhibits replacement in the
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expansion of the quoted portion, including replacement strings stored
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in shell variables.
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Backslash will escape ‘<samp>&</samp>’ in <var>string</var>; the backslash is removed
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in order to permit a literal ‘<samp>&</samp>’ in the replacement string.
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Pattern substitution performs the check for ‘<samp>&</samp>’ after expanding
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<var>string</var>,
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so users should take care to quote backslashes intended to escape
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the ‘<samp>&</samp>’ and inhibit replacement so they survive any quote removal
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performed by the expansion of <var>string</var>.
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For instance,
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Users should take care if <var>string</var> is double-quoted to avoid
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unwanted interactions between the backslash and double-quoting, since
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backslash has special meaning within double quotes.
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Pattern substitution performs the check for unquoted ‘<samp>&</samp>’ after
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expanding <var>string</var>,
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so users should ensure to properly quote any occurrences of ‘<samp>&</samp>’
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they want to be taken literally in the replacement
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and ensure any instances of ‘<samp>&</samp>’ they want to be replaced are unquoted.
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</p>
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<p>For instance,
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</p>
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<div class="example">
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<pre class="example">var=abcdef
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rep='& '
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echo ${var/abc/& }
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echo "${var/abc/& }"
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echo ${var/abc/"& "}
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echo ${var/abc/$rep}
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echo "${var/abc/$rep}"
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</pre></div>
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<p>will display three lines of "abc def", while
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<p>will display four lines of "abc def", while
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</p>
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<div class="example">
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<pre class="example">var=abcdef
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rep='& '
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echo ${var/abc/\& }
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echo "${var/abc/\& }"
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echo ${var/abc/"\& "}
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echo ${var/abc/"& "}
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echo ${var/abc/"$rep"}
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</pre></div>
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<p>will display two lines of "abc def" and a third line of "& def".
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The first two are replaced because the backslash is removed by quote
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removal performed during the expansion of <var>string</var>
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(the expansion is performed in a
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context that doesn’t take any enclosing double quotes into account, as
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with other word expansions).
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In the third case, the double quotes affect the expansion
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of ‘<samp>\&</samp>’, and, because ‘<samp>&</samp>’ is not one of the characters for
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which backslash is special in double quotes,
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the backslash survives the expansion, inhibits the replacement,
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but is removed because it is treated specially.
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One could use ‘<samp>\\&</samp>’, unquoted, as the replacement string to achive
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the same effect.
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It should rarely be necessary to enclose only <var>string</var> in double
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<p>will display four lines of "& def".
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Like the pattern removal operators, double quotes surrounding the
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replacement string quote the expanded characters, while double quotes
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enclosing the entire parameter substitution do not, since
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the expansion is performed in a
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context that doesn’t take any enclosing double quotes into account.
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</p>
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<p>Since backslash can escape ‘<samp>&</samp>’, it can also escape a backslash in
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the replacement string.
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This means that ‘<samp>\\</samp>’ will insert a literal
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backslash into the replacement, so these two <code>echo</code> commands
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</p>
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<div class="example">
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<pre class="example">var=abcdef
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rep='\\&xyz'
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echo ${var/abc/\\&xyz}
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echo ${var/abc/$rep}
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</pre></div>
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<p>will both output ‘<samp>\abcxyzdef</samp>’.
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</p>
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<p>It should rarely be necessary to enclose only <var>string</var> in double
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quotes.
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</p>
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<p>If the <code>nocasematch</code> shell option
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@@ -8626,6 +8660,9 @@ interpreted as relative to one greater than the maximum index of
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<var>name</var>, so negative indices count back from the end of the
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array, and an index of -1 references the last element.
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</p>
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<p>The ‘<samp>+=</samp>’ operator will append to an array variable when assigning
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using the compound assignment syntax; see <a href="#Shell-Parameters">Shell Parameters</a> above.
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</p>
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<p>Any element of an array may be referenced using
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<code>${<var>name</var>[<var>subscript</var>]}</code>.
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The braces are required to avoid
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@@ -9102,6 +9139,12 @@ example, <code>SIGTSTP</code>.
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</li><li> Reserved words appearing in a context where reserved words are recognized
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do not undergo alias expansion.
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</li><li> Alias expansion is performed when initially parsing a command substitution.
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The default mode generally defers it, when enabled, until the command
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substitution is executed. This means that command substitution will not
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expand aliases that are defined after the command substitution is initially
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parsed (e.g., as part of a function definition).
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</li><li> The <small>POSIX</small> <code>PS1</code> and <code>PS2</code> expansions of ‘<samp>!</samp>’ to
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the history number and ‘<samp>!!</samp>’ to ‘<samp>!</samp>’ are enabled,
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and parameter expansion is performed on the values of <code>PS1</code> and
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@@ -9338,8 +9381,8 @@ Previous: <a href="#Bash-POSIX-Mode" accesskey="p" rel="prev">Bash POSIX Mode</a
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<span id="index-Compatibility-Level"></span>
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<span id="index-Compatibility-Mode"></span>
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<p>Bash-4.0 introduced the concept of a ‘shell compatibility level’, specified
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as a set of options to the shopt builtin
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<p>Bash-4.0 introduced the concept of a <em>shell compatibility level</em>,
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specified as a set of options to the shopt builtin
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(<code>compat31</code>,
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<code>compat32</code>,
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<code>compat40</code>,
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@@ -10293,6 +10336,32 @@ variables.
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</p>
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<span id="index-variables_002c-readline"></span>
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<dl compact="compact">
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<dt id='index-active_002dregion_002dstart_002dcolor'><span><code>active-region-start-color</code><a href='#index-active_002dregion_002dstart_002dcolor' class='copiable-anchor'> ¶</a></span></dt>
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<dd><p>A string variable that controls the text color and background when displaying
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the text in the active region (see the description of
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<code>enable-active-region</code> below).
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This string must not take up any physical character positions on the display,
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so it should consist only of terminal escape sequences.
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It is output to the terminal before displaying the text in the active region.
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This variable is reset to the default value whenever the terminal type changes.
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The default value is the string that puts the terminal in standout mode,
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as obtained from the terminal’s terminfo description.
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A sample value might be ‘<samp>\e[01;33m</samp>’.
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</p>
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</dd>
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<dt id='index-active_002dregion_002dend_002dcolor'><span><code>active-region-end-color</code><a href='#index-active_002dregion_002dend_002dcolor' class='copiable-anchor'> ¶</a></span></dt>
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<dd><p>A string variable that "undoes" the effects of <code>active-region-start-color</code>
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and restores "normal" terminal display appearance after displaying text
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in the active region.
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This string must not take up any physical character positions on the display,
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so it should consist only of terminal escape sequences.
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It is output to the terminal after displaying the text in the active region.
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This variable is reset to the default value whenever the terminal type changes.
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The default value is the string that restores the terminal from standout mode,
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as obtained from the terminal’s terminfo description.
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A sample value might be ‘<samp>\e[0m</samp>’.
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</p>
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</dd>
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<dt id='index-bell_002dstyle'><span><code>bell-style</code><a href='#index-bell_002dstyle' class='copiable-anchor'> ¶</a></span></dt>
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<dd><p>Controls what happens when Readline wants to ring the terminal bell.
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If set to ‘<samp>none</samp>’, Readline never rings the bell. If set to
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@@ -10426,6 +10495,8 @@ The text between the point and mark is referred to as the <em>region</em>.
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When this variable is set to ‘<samp>On</samp>’, Readline allows certain commands
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to designate the region as <em>active</em>.
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When the region is active, Readline highlights the text in the region using
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the value of the <code>active-region-start-color</code>, which defaults to the
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string that enables
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the terminal’s standout mode.
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The active region shows the text inserted by bracketed-paste and any
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matching text found by incremental and non-incremental history searches.
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@@ -10433,11 +10504,13 @@ The default is ‘<samp>On</samp>’.
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</p>
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</dd>
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<dt id='index-enable_002dbracketed_002dpaste'><span><code>enable-bracketed-paste</code><a href='#index-enable_002dbracketed_002dpaste' class='copiable-anchor'> ¶</a></span></dt>
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<dd><p>When set to ‘<samp>On</samp>’, Readline will configure the terminal in a way
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that will enable it to insert each paste into the editing buffer as a
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single string of characters, instead of treating each character as if
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it had been read from the keyboard. This can prevent pasted characters
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from being interpreted as editing commands. The default is ‘<samp>On</samp>’.
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<dd><p>When set to ‘<samp>On</samp>’, Readline configures the terminal to insert each
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paste into the editing buffer as a single string of characters, instead
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of treating each character as if it had been read from the keyboard.
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This is called putting the terminal into <em>bracketed paste mode</em>;
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it prevents Readline from executing any editing commands bound to key
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sequences appearing in the pasted text.
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The default is ‘<samp>On</samp>’.
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</p>
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</dd>
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<dt id='index-enable_002dkeypad'><span><code>enable-keypad</code><a href='#index-enable_002dkeypad' class='copiable-anchor'> ¶</a></span></dt>
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@@ -15129,6 +15202,8 @@ Next: <a href="#Function-Index" accesskey="n" rel="next">Function Index</a>, Pre
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<tr><td></td><td valign="top"><a href="#index-_005f"><code>_</code></a>:</td><td> </td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
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<tr><td colspan="4"> <hr></td></tr>
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<tr><th id="Variable-Index_vr_letter-A">A</th><td></td><td></td></tr>
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<tr><td></td><td valign="top"><a href="#index-active_002dregion_002dend_002dcolor"><code>active-region-end-color</code></a>:</td><td> </td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
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<tr><td></td><td valign="top"><a href="#index-active_002dregion_002dstart_002dcolor"><code>active-region-start-color</code></a>:</td><td> </td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
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<tr><td></td><td valign="top"><a href="#index-auto_005fresume"><code>auto_resume</code></a>:</td><td> </td><td valign="top"><a href="#Job-Control-Variables">Job Control Variables</a></td></tr>
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<tr><td colspan="4"> <hr></td></tr>
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<tr><th id="Variable-Index_vr_letter-B">B</th><td></td><td></td></tr>
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Reference in New Issue
Block a user