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complete initial implementation of nofork command substitution (${ command; })

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Chet Ramey
2023-05-15 13:30:18 -04:00
parent c375f8f45f
commit e44e3d50de
42 changed files with 4387 additions and 3516 deletions
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@@ -3,7 +3,7 @@
</HEAD>
<BODY><TABLE WIDTH=100%>
<TR>
<TH ALIGN=LEFT width=33%>BASH(1)<TH ALIGN=CENTER width=33%>2023 April 17<TH ALIGN=RIGHT width=33%>BASH(1)
<TH ALIGN=LEFT width=33%>BASH(1)<TH ALIGN=CENTER width=33%>2023 May 14<TH ALIGN=RIGHT width=33%>BASH(1)
</TR>
</TABLE>
<BR><A HREF="#index">Index</A>
@@ -2869,8 +2869,10 @@ and
which sort the files on name, file size, modification time, access time,
inode change time, and number of blocks, respectively.
For example, a value of <B>-mtime</B> sorts the results in descending
For example, a value of <I>-mtime</I> sorts the results in descending
order by modification time (newest first).
A sort specifier of <I>nosort</I> disables sorting completely; the results
are returned in the order they are read from the file system,.
If the sort specifier is missing, it defaults to <I>name</I>,
so a value of <I>+</I> is equivalent to the null string,
and a value of <I>-</I> sorts by name in descending order.
@@ -4463,16 +4465,17 @@ expansion as described below.
<H4>Command Substitution</H4>
<I>Command substitution</I> allows the output of a command to replace
the command name. There are two forms:
the command itself.
There are two standard forms:
<DL COMPACT><DT><DD>
<P>
<B>$(</B><I>command</I><B>)</B>
</DL>
or
or (deprecated)
<DL COMPACT><DT><DD>
<B>`</B><I>command</I><B>`</B>
<B>`</B><I>command</I><B>`</B>.
</DL>
<P>
@@ -4488,7 +4491,7 @@ The command substitution <B>$(cat </B><I>file</I>) can be replaced by
the equivalent but faster <B>$(&lt; </B><I>file</I>).
<P>
When the old-style backquote form of substitution is used,
With the old-style backquote form of substitution,
backslash retains its literal meaning except when followed by
<B>$</B>,
@@ -4503,12 +4506,60 @@ When using the $(<I>command</I>) form, all characters between the
parentheses make up the command; none are treated specially.
<P>
There is an alternate form of command substitution:
<DL COMPACT><DT><DD>
<P>
<B>${</B><I>C</I> <I>command</I><B>;</B><B>}</B>
</DL>
<P>
which executes <I>command</I> in the current execution environment.
This means that side effects of <I>command</I> take effect immediately
in the current execution environment and persist in the current
environment after the command completes (e.g., the <B>exit</B> builtin
will exit the shell).
<P>
The character <I>C</I> following the open brace must be a space, tab,
newline, <B>(</B>, or <B>|</B>, and the close brace must be in a position
where a reserved word may appear (i.e., preceded by a command terminator
such as semicolon).
<B>Bash</B> allows the close brace to be joined to the remaining characters in
the word without being followed by a shell metacharacter as a reserved
word would usually require.
<P>
This type of command substitution superficially resembles executing an
unnamed shell function: local variables are created as when a shell
function is executing, and the <B>return</B> builtin forces
<I>command</I> to complete;
however, the rest of the execution environment,
including the positional parameters, is shared with the caller.
<P>
If the first character following the open brace is a <B>(</B>,
<I>command</I> is executed in a subshell, and <I>command</I> must be
terminated by a <B>)</B>. This is similar to the <B>(</B> compound
command (see <B>Compound Commands</B> above).
If the first character is a <B>|</B>, the construct expands to the
value of the <B>REPLY</B> shell variable after <I>command</I> executes,
without removing any trailing newlines,
and the standard output of <I>command</I> remains the same as in the
calling shell.
<B>Bash</B> creates <B>REPLY</B> as an initially-unset local variable when
<I>command</I> executes, and restores <B>REPLY</B> to the value it had
before the command substitution after <I>command</I> completes,
as with any local variable.
<P>
Command substitutions may be nested. To nest when using the backquoted form,
escape the inner backquotes with backslashes.
<P>
If the substitution appears within double quotes, word splitting and
pathname expansion are not performed on the results.
If the substitution appears within double quotes, <B>bash</B> does not perform
word splitting and pathname expansion on the results.
<A NAME="lbBD">&nbsp;</A>
<H4>Arithmetic Expansion</H4>
@@ -11999,7 +12050,7 @@ in the same way as <B>echo -e</B>.
<DD>
causes <B>printf</B> to output the corresponding
<I>argument</I> in a format that can be reused as shell input.
<B>%q</B> and <B>%Q</B> use the <B>$''</B> quoting style if any characters
<B>%q</B> and <B>%Q</B> use the <B>$aqaq</B> quoting style if any characters
in the argument string require it, and backslash quoting otherwise.
If the format string uses the <I>printf</I> alternate form, these two
formats quote the argument string using single quotes.
@@ -14944,7 +14995,7 @@ There may be only one active coprocess at a time.
<HR>
<TABLE WIDTH=100%>
<TR>
<TH ALIGN=LEFT width=33%>GNU Bash 5.2<TH ALIGN=CENTER width=33%>2023 April 17<TH ALIGN=RIGHT width=33%>BASH(1)
<TH ALIGN=LEFT width=33%>GNU Bash 5.2<TH ALIGN=CENTER width=33%>2023 May 14<TH ALIGN=RIGHT width=33%>BASH(1)
</TR>
</TABLE>
<HR>
@@ -15050,7 +15101,7 @@ There may be only one active coprocess at a time.
<DT><A HREF="#lbDI">BUGS</A><DD>
</DL>
<HR>
This document was created by man2html from bash.1.<BR>
Time: 18 April 2023 10:26:09 EDT
This document was created by man2html from /usr/local/src/bash/bash-20230509/doc/bash.1.<BR>
Time: 14 May 2023 15:37:14 EDT
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</HTML>